2021

  • Analysis of process-induced damage in remote laser cut carbon fibre reinforced polymers
    • B. Schmidt, M. Rose, M. Zimmermann, M. Kästner
    • Journal of Materials Processing Technology 295, 117162 (2021)
    • DOI   Abstract  

      In this paper, an approach is presented that allows for a linkage between cutting process induced damage and the mechanical properties of the machined structures. For carbon fibre reinforced polymers, the milling and remote laser cutting processes are analysed. Open hole tensile test specimens, that are either milled or remote laser cut with three different cutting parameter configurations are tested. With a two-dimensional heat conduction simulation, the temperature field resulting from laser cutting is determined and thus the thermally induced damage is quantified. Those results are compared to micro-sections. The following structural analysis is based on an anisotropic damage model and is taking the thermal pre-damage into account. For this purpose two different thermal damage modelling approaches, based on damage variables and material parameter reduction, are compared. The influence of the cutting process on the structural properties is determined and compared with experimental results. © 2021 Elsevier B.V.

      @ARTICLE{Schmidt2021,
      author={Schmidt, B. and Rose, M. and Zimmermann, M. and Kästner, M.},
      title={Analysis of process-induced damage in remote laser cut carbon fibre reinforced polymers},
      journal={Journal of Materials Processing Technology},
      year={2021},
      volume={295},
      doi={10.1016/j.jmatprotec.2021.117162},
      art_number={117162},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85103684839&doi=10.1016%2fj.jmatprotec.2021.117162&partnerID=40&md5=fce44de1b87bae944b44b6b582a8e885},
      affiliation={Institute of Solid Mechanics, TU Dresden, Dresden, Germany; Institute of Materials Science, TU Dresden, Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, Germany},
      abstract={In this paper, an approach is presented that allows for a linkage between cutting process induced damage and the mechanical properties of the machined structures. For carbon fibre reinforced polymers, the milling and remote laser cutting processes are analysed. Open hole tensile test specimens, that are either milled or remote laser cut with three different cutting parameter configurations are tested. With a two-dimensional heat conduction simulation, the temperature field resulting from laser cutting is determined and thus the thermally induced damage is quantified. Those results are compared to micro-sections. The following structural analysis is based on an anisotropic damage model and is taking the thermal pre-damage into account. For this purpose two different thermal damage modelling approaches, based on damage variables and material parameter reduction, are compared. The influence of the cutting process on the structural properties is determined and compared with experimental results. © 2021 Elsevier B.V.},
      author_keywords={Carbon fibre reinforced polymers; Process-structure-property linkage; Remote laser cutting; Thermal degradation},
      document_type={Article},
      source={Scopus},
      }

  • Doubly degenerate diffuse interface models of anisotropic surface diffusion
    • M. Salvalaglio, M. Selch, A. Voigt, S. M. Wise
    • Mathematical Methods in the Applied Sciences 44, 5406-5417 (2021)
    • DOI   Abstract  

      We extend the doubly degenerate Cahn–Hilliard (DDCH) models for isotropic surface diffusion, which yield more accurate approximations than classical degenerate Cahn–Hilliard (DCH) models, to the anisotropic case. We consider both weak and strong anisotropies and demonstrate the capabilities of the approach for these cases numerically. The proposed model provides a variational and energy dissipative approach for anisotropic surface diffusion, enabling large-scale simulations with material-specific parameters. © 2020 The Authors. Mathematical Methods in the Applied Sciences published by John Wiley & Sons Ltd

      @ARTICLE{Salvalaglio20215406,
      author={Salvalaglio, M. and Selch, M. and Voigt, A. and Wise, S.M.},
      title={Doubly degenerate diffuse interface models of anisotropic surface diffusion},
      journal={Mathematical Methods in the Applied Sciences},
      year={2021},
      volume={44},
      number={7},
      pages={5406-5417},
      doi={10.1002/mma.7118},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097852332&doi=10.1002%2fmma.7118&partnerID=40&md5=686693570aacd1683dc69ec85b7b87ce},
      affiliation={Institute of Scientific Computing, Department of Mathematics, TU Dresden, Dresden, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, Germany; Department of Mathematics, The University of Tennessee, Knoxville, TN, United States},
      abstract={We extend the doubly degenerate Cahn–Hilliard (DDCH) models for isotropic surface diffusion, which yield more accurate approximations than classical degenerate Cahn–Hilliard (DCH) models, to the anisotropic case. We consider both weak and strong anisotropies and demonstrate the capabilities of the approach for these cases numerically. The proposed model provides a variational and energy dissipative approach for anisotropic surface diffusion, enabling large-scale simulations with material-specific parameters. © 2020 The Authors. Mathematical Methods in the Applied Sciences published by John Wiley & Sons Ltd},
      author_keywords={anisotropy; degenerate Cahn–Hilliard equation; surface diffusion},
      document_type={Article},
      source={Scopus},
      }

  • Thermoelectric energy harvesting from single-walled carbon nanotube alkali-activated nanocomposites produced from industrial waste materials
    • M. Davoodabadi, I. Vareli, M. Liebscher, L. Tzounis, M. Sgarzi, A. S. Paipetis, J. Yang, G. Cuniberti, V. Mechtcherine
    • Nanomaterials 11, 1095 (2021)
    • DOI   Abstract  

      A waste-originated one-part alkali-activated nanocomposite is introduced herein as a novel thermoelectric material. For this purpose, single-walled carbon nanotubes (SWCNTs) were utilized as nanoinclusions to create an electrically conductive network within the investigated alkali-activated construction material. Thermoelectric and microstructure characteristics of SWCNT-alkali-activated nanocomposites were assessed after 28 days. Nanocomposites with 1.0 wt.% SWCNTs exhibited a multifunctional behavior, a combination of structural load-bearing, electrical conductivity, and thermoelectric response. These nanocomposites (1.0 wt.%) achieved the highest thermoelectric performance in terms of power factor (PF), compared to the lower SWCNTs’ incorporations, namely 0.1 and 0.5 wt.%. The measured electrical conductivity (σ) and Seebeck coefficient (S) were 1660 S·m−1 and 15.8 µV·K−1, respectively, which led to a power factor of 0.414 µW·m−1·K−2 . Consequently, they have been utilized as the building block of a thermoelectric generator (TEG) device, which demon-strated a maximum power output (Pout ) of 0.695 µW, with a power density (PD) of 372 nW·m−2, upon exposure to a temperature gradient of 60 K. The presented SWCNT-alkali-activated nanocomposites could establish the pathway towards waste thermal energy harvesting and future sustainable civil engineering structures. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

      @ARTICLE{Davoodabadi2021,
      author={Davoodabadi, M. and Vareli, I. and Liebscher, M. and Tzounis, L. and Sgarzi, M. and Paipetis, A.S. and Yang, J. and Cuniberti, G. and Mechtcherine, V.},
      title={Thermoelectric energy harvesting from single-walled carbon nanotube alkali-activated nanocomposites produced from industrial waste materials},
      journal={Nanomaterials},
      year={2021},
      volume={11},
      number={5},
      doi={10.3390/nano11051095},
      art_number={1095},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85104503827&doi=10.3390%2fnano11051095&partnerID=40&md5=4d65f2c8ddfa0afa9d0936ce211163b6},
      affiliation={Institute of Construction Materials, Faculty of Civil Engineering, Dresden University of Technology, Dresden, 01069, Germany; Institute for Materials Science and Max Bergmann Centre of Biomaterials, Dresden University of Technology, Dresden, 01069, Germany; Dresden Center for Nanoanalysis (DCN), Dresden University of Technology, Dresden, 01069, Germany; Department of Civil Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China; Department of Materials Science and Engineering, University of Ioannina, Ioannina, 45110, Greece; Center for Advancing Electronics Dresden (CfAED), Dresden University of Technology, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden University of Technology, Dresden, 01069, Germany},
      abstract={A waste-originated one-part alkali-activated nanocomposite is introduced herein as a novel thermoelectric material. For this purpose, single-walled carbon nanotubes (SWCNTs) were utilized as nanoinclusions to create an electrically conductive network within the investigated alkali-activated construction material. Thermoelectric and microstructure characteristics of SWCNT-alkali-activated nanocomposites were assessed after 28 days. Nanocomposites with 1.0 wt.% SWCNTs exhibited a multifunctional behavior, a combination of structural load-bearing, electrical conductivity, and thermoelectric response. These nanocomposites (1.0 wt.%) achieved the highest thermoelectric performance in terms of power factor (PF), compared to the lower SWCNTs’ incorporations, namely 0.1 and 0.5 wt.%. The measured electrical conductivity (σ) and Seebeck coefficient (S) were 1660 S·m−1 and 15.8 µV·K−1, respectively, which led to a power factor of 0.414 µW·m−1·K−2 . Consequently, they have been utilized as the building block of a thermoelectric generator (TEG) device, which demon-strated a maximum power output (Pout ) of 0.695 µW, with a power density (PD) of 372 nW·m−2, upon exposure to a temperature gradient of 60 K. The presented SWCNT-alkali-activated nanocomposites could establish the pathway towards waste thermal energy harvesting and future sustainable civil engineering structures. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.},
      author_keywords={Alkali-activated nanocomposites; Green construction; Multifunctional waste materials; Single-walled carbon nanotubes; Thermal energy harvesting; Thermoelectric generator},
      document_type={Article},
      source={Scopus},
      }

  • Searching for Aquamelt Behavior among Silklike Biomimetics during Fibrillation under Flow
    • S. Donets, O. Guskova, J. -U. Sommer
    • The journal of physical chemistry. B 125, 3238-3250 (2021)
    • DOI   Abstract  

      In this paper, we elucidate a generic mechanism behind strain-induced phase transition in aqueous solutions of silk-inspired biomimetics by atomistic molecular dynamics simulations. We show the results of modeling of homopeptides polyglycine Gly30 and polyalanine Ala30 and a heteropeptide (Gly-Ala-Gly-Ala-Gly-Ser)5, i.e., the simplest and yet relevant sequences that could mimic the behavior of natural silk under stress conditions. First, we analyze hydrophobicities of the sequences by calculating the Gibbs free energy of hydration and inspecting the interchain hydrogen bonding and hydration by water. Second, the force-extension profiles are scanned and compared with the results for poly(ethylene oxide), the synthetic polymer for which the aquamelt behavior has been proved recently. Additionally, the conformational transitions of oligopeptides from coiled to extended states are characterized by a generalized order parameter and by the dependence of the solvent-accessible surface area of the chains on applied stretching. Fibrillation itself is surveyed using both the two-dimensional interchain pair correlation function and the SAXS/WAXS patterns for the aggregates formed under stress. These are compared with experimental data found in the literature on fibril structure of silk composite materials doped with oligoalanine peptides. Our results show that tensile stress introduced into aqueous oligopeptide solutions facilitates interchain interactions. The oligopeptides display both a greater resistance to extension as compared to poly(ethylene oxide) and a reduced ability for hydrogen bonding of the stretched chains between oligomers and with water. Fiber formation is proved for all simulated objects, but the most structured one is made of a heteropeptide (Gly-Ala-Gly-Ala-Gly-Ser)5: For this sequence, we obtain the highest degree of the secondary structure motifs in the fiber. We conclude that this is the most promising candidate among considered sequences to find the aquamelt behavior in further experimental studies.

      @ARTICLE{Donets20213238,
      author={Donets, S. and Guskova, O. and Sommer, J.-U.},
      title={Searching for Aquamelt Behavior among Silklike Biomimetics during Fibrillation under Flow},
      journal={The journal of physical chemistry. B},
      year={2021},
      volume={125},
      number={12},
      pages={3238-3250},
      doi={10.1021/acs.jpcb.1c00647},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85103682088&doi=10.1021%2facs.jpcb.1c00647&partnerID=40&md5=5102ec0af2bcc8a39e3fdf90b4166bb5},
      affiliation={Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Institute of Theoretical Physics, Technische Universität Dresden ,Zellescher Weg 17, Dresden, 01069, Germany},
      abstract={In this paper, we elucidate a generic mechanism behind strain-induced phase transition in aqueous solutions of silk-inspired biomimetics by atomistic molecular dynamics simulations. We show the results of modeling of homopeptides polyglycine Gly30 and polyalanine Ala30 and a heteropeptide (Gly-Ala-Gly-Ala-Gly-Ser)5, i.e., the simplest and yet relevant sequences that could mimic the behavior of natural silk under stress conditions. First, we analyze hydrophobicities of the sequences by calculating the Gibbs free energy of hydration and inspecting the interchain hydrogen bonding and hydration by water. Second, the force-extension profiles are scanned and compared with the results for poly(ethylene oxide), the synthetic polymer for which the aquamelt behavior has been proved recently. Additionally, the conformational transitions of oligopeptides from coiled to extended states are characterized by a generalized order parameter and by the dependence of the solvent-accessible surface area of the chains on applied stretching. Fibrillation itself is surveyed using both the two-dimensional interchain pair correlation function and the SAXS/WAXS patterns for the aggregates formed under stress. These are compared with experimental data found in the literature on fibril structure of silk composite materials doped with oligoalanine peptides. Our results show that tensile stress introduced into aqueous oligopeptide solutions facilitates interchain interactions. The oligopeptides display both a greater resistance to extension as compared to poly(ethylene oxide) and a reduced ability for hydrogen bonding of the stretched chains between oligomers and with water. Fiber formation is proved for all simulated objects, but the most structured one is made of a heteropeptide (Gly-Ala-Gly-Ala-Gly-Ser)5: For this sequence, we obtain the highest degree of the secondary structure motifs in the fiber. We conclude that this is the most promising candidate among considered sequences to find the aquamelt behavior in further experimental studies.},
      document_type={Article},
      source={Scopus},
      }

  • Theoretical Insight into High-Efficiency Triple-Junction Tandem Solar Cells via the Band Engineering of Antimony Chalcogenides
    • Y. Cao, C. Liu, J. Jiang, X. Zhu, J. Zhou, J. Ni, J. Zhang, J. Pang, M. H. Rummeli, W. Zhou, H. Liu, G. Cuniberti
    • Solar RRL 5, 2000800 (2021)
    • DOI   Abstract  

      Antimony chalcogenides have become a family of promising photoelectric materials for high-efficiency solar cells. To date, single-junction solar cells based on individual antimony selenide or sulfide are dominant and show limited photoelectric conversion efficiency. Therefore, great gaps remain for the multiple junction solar cells. Herein, triple-junction antimony chalcogenides-based solar cells are designed and optimized with a theoretical efficiency of 32.98% through band engineering strategies with Sb2S3/Sb2(S0.7Se0.3)3/Sb2Se3 stacking. The optimum Se content of the mid-cell should be maintained low, i.e., 30% for achieving a low defect density in an absorber layer. Therefore, Sb2(S0.7Se0.3)3-based mid solar cells have contributed to elevate the external quantum efficiency in triple-junction devices by the full utilization of the solar spectrum. In a single-junction solar cell, the bandgap gradient is regulated through the Se content gradient along the depth profile of Sb2(S1−xSex)3. Besides, an increasing Se content profile provides an additional built-in electric field for boosting hole charge carrier collection. Thus, the high charge carrier generation rate leads to a 17.96% improvement in the conversion efficiency compared with a conventional cell. This work may pave the way to boost the conversion efficiency of antimony chalcogenides-based solar cells to their theoretical limits. © 2021 Wiley-VCH GmbH

      @ARTICLE{Cao2021,
      author={Cao, Y. and Liu, C. and Jiang, J. and Zhu, X. and Zhou, J. and Ni, J. and Zhang, J. and Pang, J. and Rummeli, M.H. and Zhou, W. and Liu, H. and Cuniberti, G.},
      title={Theoretical Insight into High-Efficiency Triple-Junction Tandem Solar Cells via the Band Engineering of Antimony Chalcogenides},
      journal={Solar RRL},
      year={2021},
      volume={5},
      number={4},
      doi={10.1002/solr.202000800},
      art_number={2000800},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85101602611&doi=10.1002%2fsolr.202000800&partnerID=40&md5=93616af3627d11f4dca5744b9520ddf4},
      affiliation={Key Laboratory of Modern Power System Simulation and Control & Renewable Energy Technology, Ministry of Education (Northeast Electric Power University), Jilin, 132012, China; School of Electrical Engineering, Northeast Electric Power University, Jilin, 132012, China; School of Chemical Engineering, Northeast Electric Power University, Jilin, 132012, China; College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300350, China; Collaborative Innovation Center of Technology and Equipment for Biological Diagnosis and Therapy in Universities of Shandong, Institute for Advanced Interdisciplinary Research (iAIR), University of Jinan, Jinan, 250022, China; College of Energy, Soochow Institute for Energy and Materials Innovations Soochow University, Suzhou, 215006, China; Key Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu Province, Soochow University, Suzhou, 215006, China; Centre of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie Sklodowskiej 34, Zabrze, 41-819, Poland; Institute for Complex Materials, IFW Dresden, 20 Helmholtz Strasse, Dresden, 01069, Germany; Institute of Environmental Technology, VŠB-Technical University of Ostrava, 17. Listopadu 15, Ostrava, 708 33, Czech Republic; State Key Laboratory of Crystal Materials, Center of Bio & Micro/Nano Functional Materials, Shandong University, 27 Shandanan Road, Jinan, 250100, China; Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={Antimony chalcogenides have become a family of promising photoelectric materials for high-efficiency solar cells. To date, single-junction solar cells based on individual antimony selenide or sulfide are dominant and show limited photoelectric conversion efficiency. Therefore, great gaps remain for the multiple junction solar cells. Herein, triple-junction antimony chalcogenides-based solar cells are designed and optimized with a theoretical efficiency of 32.98% through band engineering strategies with Sb2S3/Sb2(S0.7Se0.3)3/Sb2Se3 stacking. The optimum Se content of the mid-cell should be maintained low, i.e., 30% for achieving a low defect density in an absorber layer. Therefore, Sb2(S0.7Se0.3)3-based mid solar cells have contributed to elevate the external quantum efficiency in triple-junction devices by the full utilization of the solar spectrum. In a single-junction solar cell, the bandgap gradient is regulated through the Se content gradient along the depth profile of Sb2(S1−xSex)3. Besides, an increasing Se content profile provides an additional built-in electric field for boosting hole charge carrier collection. Thus, the high charge carrier generation rate leads to a 17.96% improvement in the conversion efficiency compared with a conventional cell. This work may pave the way to boost the conversion efficiency of antimony chalcogenides-based solar cells to their theoretical limits. © 2021 Wiley-VCH GmbH},
      author_keywords={antimony chalcogenides; band engineering; quantum efficiencies; thin films; triple-junction tandem solar cells},
      document_type={Article},
      source={Scopus},
      }

  • Multi-walled carbon nanotube dispersion methodologies in alkaline media and their influence on mechanical reinforcement of alkali-activated nanocomposites
    • M. Davoodabadi, M. Liebscher, S. Hampel, M. Sgarzi, A. B. Rezaie, D. Wolf, G. Cuniberti, V. Mechtcherine, J. Yang
    • Composites Part B: Engineering 209, 108559 (2021)
    • DOI   Abstract  

      The focus of present research is the establishment of a practical procedure for effective incorporation of multi-walled carbon nanotubes (MWCNTs) into alkali-activated materials (AAMs) with the aim of mechanical reinforcement. Investigated composite in this work was an alkali-activated matrix composed of fly ash (FA) and ground-granulated blast furnace-slag (GGBS) as solid aluminium-calcium-silicate precursors along with highly concentrated sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) as liquid alkaline activators. Na2SiO3, NaOH, and a combination of them were used for dispersion of MWCNTs. An anionic surfactant, naphthalene sulfonate (NS), and ultrasonication were applied to assist in the preparation of nanofluids. Optical microscopy, integral light transmission (ILT), and Fourier-transform infrared spectroscopy (FTIR) were performed to assess the colloidal behaviour of MWCNTs in the nanofluids. The possible dispersion mechanisms were furthermore hypothesised for each alkaline medium. Based on the outcomes, MWCNTs had the best dispersion performance in the Na2SiO3 based nanofluids. The relevant nanocomposites accordingly, in comparison to the other preparation methodologies in this research, indicated the highest improvements in flexural (65%) and compressive (30%) strengths as a consequence of 0.050 wt% MWCNT incorporation. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) further clarified the reinforcement functionality and microstructure refinement of the MWCNTs dispersed in the Na2SiO3 based nanofluids. Altogether, this paper represents a broad insight concerning a better understanding of MWCNTs’ interactions in alkaline activators, i.e. dispersion media, and AAMs, i.e. host matrices, to obtain the highest possible mechanical and microstructural performance of reinforced nanocomposites. © 2021 Elsevier Ltd

      @ARTICLE{Davoodabadi2021,
      author={Davoodabadi, M. and Liebscher, M. and Hampel, S. and Sgarzi, M. and Rezaie, A.B. and Wolf, D. and Cuniberti, G. and Mechtcherine, V. and Yang, J.},
      title={Multi-walled carbon nanotube dispersion methodologies in alkaline media and their influence on mechanical reinforcement of alkali-activated nanocomposites},
      journal={Composites Part B: Engineering},
      year={2021},
      volume={209},
      doi={10.1016/j.compositesb.2020.108559},
      art_number={108559},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85100019051&doi=10.1016%2fj.compositesb.2020.108559&partnerID=40&md5=815c8fb302e5a298cab412dbfeb67097},
      affiliation={Department of Civil Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China; Institute of Construction Materials, Faculty of Civil Engineering, TU Dresden, Dresden, 01069, Germany; Leibniz Institute for Solid State and Materials Research, Dresden, 01069, Germany; Institute for Materials Science and Max Bergmann Centre of Biomaterials, TU Dresden, Dresden, 01069, Germany; Center for Advancing Electronics Dresden (CfAED), TU Dresden, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01069, Germany},
      abstract={The focus of present research is the establishment of a practical procedure for effective incorporation of multi-walled carbon nanotubes (MWCNTs) into alkali-activated materials (AAMs) with the aim of mechanical reinforcement. Investigated composite in this work was an alkali-activated matrix composed of fly ash (FA) and ground-granulated blast furnace-slag (GGBS) as solid aluminium-calcium-silicate precursors along with highly concentrated sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) as liquid alkaline activators. Na2SiO3, NaOH, and a combination of them were used for dispersion of MWCNTs. An anionic surfactant, naphthalene sulfonate (NS), and ultrasonication were applied to assist in the preparation of nanofluids. Optical microscopy, integral light transmission (ILT), and Fourier-transform infrared spectroscopy (FTIR) were performed to assess the colloidal behaviour of MWCNTs in the nanofluids. The possible dispersion mechanisms were furthermore hypothesised for each alkaline medium. Based on the outcomes, MWCNTs had the best dispersion performance in the Na2SiO3 based nanofluids. The relevant nanocomposites accordingly, in comparison to the other preparation methodologies in this research, indicated the highest improvements in flexural (65%) and compressive (30%) strengths as a consequence of 0.050 wt% MWCNT incorporation. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) further clarified the reinforcement functionality and microstructure refinement of the MWCNTs dispersed in the Na2SiO3 based nanofluids. Altogether, this paper represents a broad insight concerning a better understanding of MWCNTs’ interactions in alkaline activators, i.e. dispersion media, and AAMs, i.e. host matrices, to obtain the highest possible mechanical and microstructural performance of reinforced nanocomposites. © 2021 Elsevier Ltd},
      author_keywords={Alkali-activated materials; Carbon nanotubes; Colloidal interactions; Mechanical properties; Microstructure; Nanocomposites; Nanofluids},
      document_type={Article},
      source={Scopus},
      }

  • Pressure-induced structural transition and antiferromagnetism in elemental terbium
    • D. P. Kozlenko, V. Y. Yushankhai, R. Hayn, M. Richter, N. O. Golosova, S. E. Kichanov, E. V. Lukin, B. N. Savenko
    • Physical Review Materials 5, 034402 (2021)
    • DOI   Abstract  

      Structural and magnetic properties of rare-earth Tb metal have been studied by means of neutron powder diffraction at pressures up to 9 GPa in the temperature range 7-290 K. A structural phase transition from the initial hexagonal close-packed (hcp) to the Sm-type rhombohedral phase develops gradually at high pressures above 4 GPa. The initial ferromagnetic state in the hcp phase is suppressed and an antiferromagnetic state is developed in the pressure-induced phase. In the Sm-type structure and the temperature range below TMO=110K (at 9 GPa) down to 50 K, long-range order of Tb magnetic moments located in the layers resembling hexagonal close-packing type is formed with a propagation vector kAF1=(0012), while the layers resembling cubic close-packing type remain disordered. This partial disorder disappears at temperatures below 50 K when magnetic order, including the moments in the latter layers, develops with a propagation vector kAF2=(12012). The relative stability of the hcp and Sm-type structures under pressure was examined by density functional theory calculations, providing significant support to the experimental findings. The calculated bulk moduli of the hcp and Sm-type phases are close to the experimentally determined ones and the estimate P0≈4GPa obtained for the equilibrium transition pressure is close to the onset pressure found in real material. The volume collapse at the hcp to Sm-type transition was evaluated to amount to 0.4Å3 per atom. © 2021 American Physical Society.

      @ARTICLE{Kozlenko2021,
      author={Kozlenko, D.P. and Yushankhai, V.Y. and Hayn, R. and Richter, M. and Golosova, N.O. and Kichanov, S.E. and Lukin, E.V. and Savenko, B.N.},
      title={Pressure-induced structural transition and antiferromagnetism in elemental terbium},
      journal={Physical Review Materials},
      year={2021},
      volume={5},
      number={3},
      doi={10.1103/PhysRevMaterials.5.034402},
      art_number={034402},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85104256814&doi=10.1103%2fPhysRevMaterials.5.034402&partnerID=40&md5=a7a9ee1f101d77ea5cf46a7939b58a5e},
      affiliation={Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, 141980, Russian Federation; Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna, 141980, Russian Federation; Dubna State University, Dubna, 141982, Russian Federation; Aix-Marseille Université, CNRS, IM2NP-UMR7334, Marseille Cedex 20, 13397, France; Leibniz IFW Dresden, Helmholtzstraße 20, Dresden, D-01069, Germany; Max-Planck Institut für Physik Komplexer Systeme, Dresden, D-01187, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, D-01062, Germany},
      abstract={Structural and magnetic properties of rare-earth Tb metal have been studied by means of neutron powder diffraction at pressures up to 9 GPa in the temperature range 7-290 K. A structural phase transition from the initial hexagonal close-packed (hcp) to the Sm-type rhombohedral phase develops gradually at high pressures above 4 GPa. The initial ferromagnetic state in the hcp phase is suppressed and an antiferromagnetic state is developed in the pressure-induced phase. In the Sm-type structure and the temperature range below TMO=110K (at 9 GPa) down to 50 K, long-range order of Tb magnetic moments located in the layers resembling hexagonal close-packing type is formed with a propagation vector kAF1=(0012), while the layers resembling cubic close-packing type remain disordered. This partial disorder disappears at temperatures below 50 K when magnetic order, including the moments in the latter layers, develops with a propagation vector kAF2=(12012). The relative stability of the hcp and Sm-type structures under pressure was examined by density functional theory calculations, providing significant support to the experimental findings. The calculated bulk moduli of the hcp and Sm-type phases are close to the experimentally determined ones and the estimate P0≈4GPa obtained for the equilibrium transition pressure is close to the onset pressure found in real material. The volume collapse at the hcp to Sm-type transition was evaluated to amount to 0.4Å3 per atom. © 2021 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Highly sensitive room temperature ammonia gas sensor using pristine graphene: The role of biocompatible stabilizer
    • S. Huang, L. A. Panes-Ruiz, A. Croy, M. Löffler, V. Khavrus, V. Bezugly, G. Cuniberti
    • Carbon 173, 262-270 (2021)
    • DOI   Abstract  

      Graphene has attracted extraordinary attention for gas sensing due to its large specific surface area as well as its high charge carrier mobility. Nonetheless, in most cases, graphene derivatives, such as reduced graphene oxide (rGO), were employed as sensing elements instead of pristine graphene. In this contribution, pristine graphene noncovalently functionalized by a biocompatible stabilizer (flavin monocleotide sodium salt, FMNS) was produced for the application as NH3 sensing materials in a chemiresistor type gas sensor. Detailed characterizations indicate that the graphene flakes exhibit good structural quality with few defects. The optimized ammonia sensors demonstrate outstanding performance: ultralow limit-of-detection (1.6 ppm), excellent sensitivity (2.8%, 10 ppm; 18.5%, 1000 ppm), reproducibility, reversibility, low power consumption (work temperature, 25 °C) as well as low cost. Additionally, the roles of FMNS from graphene preparation to NH3 sensing are elucidated via all-atom molecular dynamics simulations: (1) stabilizer for the graphene dispersion, (2) p-type dopant for graphene-based sensing element, and (3) active adsorption sites for NH3 gas sensing. This contribution provides an efficient strategy to design highly sensitive pristine graphene-based NH3 gas sensors utilizing FMNS-like molecules, involving a facile and environmentally friendly process, biocompatible materials, low cost equipment, and scale-up capability. © 2020 Elsevier Ltd

      @ARTICLE{Huang2021262,
      author={Huang, S. and Panes-Ruiz, L.A. and Croy, A. and Löffler, M. and Khavrus, V. and Bezugly, V. and Cuniberti, G.},
      title={Highly sensitive room temperature ammonia gas sensor using pristine graphene: The role of biocompatible stabilizer},
      journal={Carbon},
      year={2021},
      volume={173},
      pages={262-270},
      doi={10.1016/j.carbon.2020.11.001},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096354195&doi=10.1016%2fj.carbon.2020.11.001&partnerID=40&md5=de149cf81d3b3d020bee77e038e5b41f},
      affiliation={Institute for Materials Science and Max Bergmann Center for Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Nanoanalysis, Center for Advancing Electronics Dresden (CfAED), TU Dresden, Dresden, 01187, Germany; Life Science Inkubator Sachsen GmbH & Co. KG, Tatzberg 47, Dresden, 01307, Germany; Center for Advancing Electronics Dresden (cfAED), TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={Graphene has attracted extraordinary attention for gas sensing due to its large specific surface area as well as its high charge carrier mobility. Nonetheless, in most cases, graphene derivatives, such as reduced graphene oxide (rGO), were employed as sensing elements instead of pristine graphene. In this contribution, pristine graphene noncovalently functionalized by a biocompatible stabilizer (flavin monocleotide sodium salt, FMNS) was produced for the application as NH3 sensing materials in a chemiresistor type gas sensor. Detailed characterizations indicate that the graphene flakes exhibit good structural quality with few defects. The optimized ammonia sensors demonstrate outstanding performance: ultralow limit-of-detection (1.6 ppm), excellent sensitivity (2.8%, 10 ppm; 18.5%, 1000 ppm), reproducibility, reversibility, low power consumption (work temperature, 25 °C) as well as low cost. Additionally, the roles of FMNS from graphene preparation to NH3 sensing are elucidated via all-atom molecular dynamics simulations: (1) stabilizer for the graphene dispersion, (2) p-type dopant for graphene-based sensing element, and (3) active adsorption sites for NH3 gas sensing. This contribution provides an efficient strategy to design highly sensitive pristine graphene-based NH3 gas sensors utilizing FMNS-like molecules, involving a facile and environmentally friendly process, biocompatible materials, low cost equipment, and scale-up capability. © 2020 Elsevier Ltd},
      author_keywords={Ammonia gas sensor; Biocompatibility; Flavin mononucleotide sodium; Graphene; Molecular dynamic simulations},
      document_type={Article},
      source={Scopus},
      }

  • Nanoscale Phononic Analog of the Ranque-Hilsch Vortex Tube
    • L. Medrano Sandonas, Á. Rodríguez Méndez, R. Gutierrez, G. Cuniberti, V. Mujica
    • Physical Review Applied 15, 034008 (2021)
    • DOI   Abstract  

      Thermal management is a current global challenge that must be addressed exhaustively. We propose the design of a nanoscale phononic analog of the Ranque-Hilsch vortex tube in which heat flowing at a given temperature is split into two different streams going to the two ends of the device, inducing a temperature asymmetry. Our nanoscale prototype consists of two carbon nanotubes (capped and open) connected by molecular chains. The results show that the structural asymmetry in the contact regions is the key factor for producing the flux asymmetry and, hence, the induced temperature-bias effect. The effect can be controlled by tuning the thermal-equilibration temperature, the number of chains, and the chain length. Deposition on a substrate adds another variable to the manipulation of the flux asymmetry but the effect vanishes at very large substrate temperatures. Our study yields insights into the thermal management in nanoscale materials, especially the crucial issue of whether the thermal asymmetry can survive phonon scattering over relatively long distances, and thus provides a starting point for the design of a nanoscale phononic analog of the Ranque-Hilsch vortex tube. © 2021 American Physical Society.

      @ARTICLE{MedranoSandonas2021,
      author={Medrano Sandonas, L. and Rodríguez Méndez, Á. and Gutierrez, R. and Cuniberti, G. and Mujica, V.},
      title={Nanoscale Phononic Analog of the Ranque-Hilsch Vortex Tube},
      journal={Physical Review Applied},
      year={2021},
      volume={15},
      number={3},
      doi={10.1103/PhysRevApplied.15.034008},
      art_number={034008},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85103436975&doi=10.1103%2fPhysRevApplied.15.034008&partnerID=40&md5=7dc6e35c0c752d2389bc69bfeec8480f},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, Tu Dresden, Dresden, 01062, Germany; Department of Physics and Materials Science, University of Luxembourg, Luxembourg, L-1511, Luxembourg; Center for Advancing Electronics Dresden, Tu Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Tu Dresden, Dresden, 01062, Germany; School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, United States; Kimika Fakultatea, Euskal Herriko Unibertsitatea and Donostia International Physics Center (DIPC), P. K. 1072, Donostia, Euskadi, 20080, Spain},
      abstract={Thermal management is a current global challenge that must be addressed exhaustively. We propose the design of a nanoscale phononic analog of the Ranque-Hilsch vortex tube in which heat flowing at a given temperature is split into two different streams going to the two ends of the device, inducing a temperature asymmetry. Our nanoscale prototype consists of two carbon nanotubes (capped and open) connected by molecular chains. The results show that the structural asymmetry in the contact regions is the key factor for producing the flux asymmetry and, hence, the induced temperature-bias effect. The effect can be controlled by tuning the thermal-equilibration temperature, the number of chains, and the chain length. Deposition on a substrate adds another variable to the manipulation of the flux asymmetry but the effect vanishes at very large substrate temperatures. Our study yields insights into the thermal management in nanoscale materials, especially the crucial issue of whether the thermal asymmetry can survive phonon scattering over relatively long distances, and thus provides a starting point for the design of a nanoscale phononic analog of the Ranque-Hilsch vortex tube. © 2021 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Investigating a Combined Stochastic Nucleation and Molecular Dynamics-Based Equilibration Approach for Constructing Large-Scale Polycrystalline Films
    • K. S. Schellhammer, G. Cuniberti, F. Ortmann
    • Journal of Chemical Theory and Computation 17, 1266-1275 (2021)
    • DOI   Abstract  

      The morphology of small-molecule organic semiconducting materials can vary from single crystals via polycrystalline films with varying grain sizes to amorphous structures, depending on the process conditions. This structural variety affects the electronic properties and, thus, the performance of organic electronic devices. A nucleation-equilibration approach is investigated, whose focus is on the construction of morphologies with controlled variations in the average grain size. Its computational requirements are low because nucleation is purely based on geometrical considerations, thus allowing the construction of model systems of experimentally relevant sizes. Its application is demonstrated for C60 and pentacene by generating single-component films that vary from amorphous to crystalline structures. It is further generalized to two-component films and applied to C60: Pentacene blends as well as dilute n-doped C60 structures. When combined with electronic structure calculations in the future, the nucleation-equilibration approach can offer insights into the impact of polycrystallinity on electronic and charge-transport properties in the absence of any knowledge about the growth mechanism and for a broad set of systems. © 2021 American Chemical Society. All rights reserved.

      @ARTICLE{Schellhammer20211266,
      author={Schellhammer, K.S. and Cuniberti, G. and Ortmann, F.},
      title={Investigating a Combined Stochastic Nucleation and Molecular Dynamics-Based Equilibration Approach for Constructing Large-Scale Polycrystalline Films},
      journal={Journal of Chemical Theory and Computation},
      year={2021},
      volume={17},
      number={2},
      pages={1266-1275},
      doi={10.1021/acs.jctc.0c01196},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85100038120&doi=10.1021%2facs.jctc.0c01196&partnerID=40&md5=5f3d106a1df883af1e0973956e04daea},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, 01062, Germany; Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, Garching, 85748, Germany},
      abstract={The morphology of small-molecule organic semiconducting materials can vary from single crystals via polycrystalline films with varying grain sizes to amorphous structures, depending on the process conditions. This structural variety affects the electronic properties and, thus, the performance of organic electronic devices. A nucleation-equilibration approach is investigated, whose focus is on the construction of morphologies with controlled variations in the average grain size. Its computational requirements are low because nucleation is purely based on geometrical considerations, thus allowing the construction of model systems of experimentally relevant sizes. Its application is demonstrated for C60 and pentacene by generating single-component films that vary from amorphous to crystalline structures. It is further generalized to two-component films and applied to C60: Pentacene blends as well as dilute n-doped C60 structures. When combined with electronic structure calculations in the future, the nucleation-equilibration approach can offer insights into the impact of polycrystallinity on electronic and charge-transport properties in the absence of any knowledge about the growth mechanism and for a broad set of systems. © 2021 American Chemical Society. All rights reserved.},
      document_type={Article},
      source={Scopus},
      }

  • Surface-Phonon-Induced Rotational Dissipation for Nanoscale Solid-State Gears
    • H. -H. Lin, A. Croy, R. Gutierrez, G. Cuniberti
    • Physical Review Applied 15, 024053 (2021)
    • DOI   Abstract  

      Compared to nanoscale friction of translational motion, the mechanisms of rotational friction have received less attention. Such motion becomes an important issue for the miniaturization of mechanical machinery that often involves rotating gears. In this study, molecular-dynamics simulations are performed to explore rotational friction for solid-state gears rotating on top of different substrates. In each case, viscous damping of the rotational motion is observed and found to be induced by the pure van der Waals interaction between the gear and the substrate. The influence of different gear sizes and various substrate materials is investigated. Furthermore, the rigidities of the gear and the substrate are found to give rise to different dissipation channels. Finally, it is shown that the dominant contribution to the dissipation is related to the excitation of low-frequency surface phonons in the substrate. © 2021 American Physical Society.

      @ARTICLE{Lin2021,
      author={Lin, H.-H. and Croy, A. and Gutierrez, R. and Cuniberti, G.},
      title={Surface-Phonon-Induced Rotational Dissipation for Nanoscale Solid-State Gears},
      journal={Physical Review Applied},
      year={2021},
      volume={15},
      number={2},
      doi={10.1103/PhysRevApplied.15.024053},
      art_number={024053},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85102407399&doi=10.1103%2fPhysRevApplied.15.024053&partnerID=40&md5=81615e817c02d1610197452435b65dfe},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01069, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Compared to nanoscale friction of translational motion, the mechanisms of rotational friction have received less attention. Such motion becomes an important issue for the miniaturization of mechanical machinery that often involves rotating gears. In this study, molecular-dynamics simulations are performed to explore rotational friction for solid-state gears rotating on top of different substrates. In each case, viscous damping of the rotational motion is observed and found to be induced by the pure van der Waals interaction between the gear and the substrate. The influence of different gear sizes and various substrate materials is investigated. Furthermore, the rigidities of the gear and the substrate are found to give rise to different dissipation channels. Finally, it is shown that the dominant contribution to the dissipation is related to the excitation of low-frequency surface phonons in the substrate. © 2021 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Predicting the bulk modulus of single-layer covalent organic frameworks with square-lattice topology from molecular building-block properties
    • A. Raptakis, A. Dianat, A. Croy, G. Cuniberti
    • Nanoscale 13, 1077-1085 (2021)
    • DOI   Abstract  

      Two-dimensional Covalent Organic Frameworks (2D COFs) have attracted a lot of interest because of their potential for a broad range of applications. Different combinations of their molecular building blocks can lead to new materials with different physical and chemical properties. In this study, the elasticity of different single-layer tetrabenzoporphyrin (H2-TBPor) and phthalocyanine (H2-Pc) based 2D COFs is numerically investigated using a density-functional based tight-binding approach. Specifically, we calculate the 2D bulk modulus and the equivalent spring constants of the respective molecular building-blocks. Using a spring network model we are able to predict the 2D bulk modulus based on the properties of the isolated molecules. This provides a path to optimize elastic properties of 2D COFs. This journal is © The Royal Society of Chemistry.

      @ARTICLE{Raptakis20211077,
      author={Raptakis, A. and Dianat, A. and Croy, A. and Cuniberti, G.},
      title={Predicting the bulk modulus of single-layer covalent organic frameworks with square-lattice topology from molecular building-block properties},
      journal={Nanoscale},
      year={2021},
      volume={13},
      number={2},
      pages={1077-1085},
      doi={10.1039/d0nr07666j},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85099792497&doi=10.1039%2fd0nr07666j&partnerID=40&md5=28767b6e0d30412257f7be65866af2bc},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={Two-dimensional Covalent Organic Frameworks (2D COFs) have attracted a lot of interest because of their potential for a broad range of applications. Different combinations of their molecular building blocks can lead to new materials with different physical and chemical properties. In this study, the elasticity of different single-layer tetrabenzoporphyrin (H2-TBPor) and phthalocyanine (H2-Pc) based 2D COFs is numerically investigated using a density-functional based tight-binding approach. Specifically, we calculate the 2D bulk modulus and the equivalent spring constants of the respective molecular building-blocks. Using a spring network model we are able to predict the 2D bulk modulus based on the properties of the isolated molecules. This provides a path to optimize elastic properties of 2D COFs. This journal is © The Royal Society of Chemistry.},
      document_type={Article},
      source={Scopus},
      }

  • Magneto-mechanical coupling in magneto-active elastomers
    • P. Metsch, D. Romeis, K. A. Kalina, A. Raßloff, M. Saphiannikova, M. Kästner
    • Materials 14, 1-27 , 434 (2021)
    • DOI   Abstract  

      In the present work, the magneto-mechanical coupling in magneto-active elastomers is investigated from two different modeling perspectives: a micro-continuum and a particle–interaction approach. Since both strategies differ significantly in their basic assumptions and the resolution of the problem under investigation, they are introduced in a concise manner and their capabilities are illustrated by means of representative examples. To motivate the application of these strategies within a hybrid multiscale framework for magneto-active elastomers, their interchangeability is then examined in a systematic comparison of the model predictions with regard to the magneto-deformation of chain-like helical structures in an elastomer surrounding. The presented results show a remarkable agreement of both modeling approaches and help to provide an improved understanding of the interactions in magneto-active elastomers with chain-like microstructures. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

      @ARTICLE{Metsch20211,
      author={Metsch, P. and Romeis, D. and Kalina, K.A. and Raßloff, A. and Saphiannikova, M. and Kästner, M.},
      title={Magneto-mechanical coupling in magneto-active elastomers},
      journal={Materials},
      year={2021},
      volume={14},
      number={2},
      pages={1-27},
      doi={10.3390/ma14020434},
      art_number={434},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85099543750&doi=10.3390%2fma14020434&partnerID=40&md5=bfad931a9d4d3ff37f4ac5c5e42885a9},
      affiliation={Institute of Solid Mechanics, Technische Universität Dresden, Dresden, 01062, Germany; Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Strasse 6, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={In the present work, the magneto-mechanical coupling in magneto-active elastomers is investigated from two different modeling perspectives: a micro-continuum and a particle–interaction approach. Since both strategies differ significantly in their basic assumptions and the resolution of the problem under investigation, they are introduced in a concise manner and their capabilities are illustrated by means of representative examples. To motivate the application of these strategies within a hybrid multiscale framework for magneto-active elastomers, their interchangeability is then examined in a systematic comparison of the model predictions with regard to the magneto-deformation of chain-like helical structures in an elastomer surrounding. The presented results show a remarkable agreement of both modeling approaches and help to provide an improved understanding of the interactions in magneto-active elastomers with chain-like microstructures. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.},
      author_keywords={Magneto-active elastomers; Magneto-deformation; Magneto-mechanical coupling; Magneto-striction},
      document_type={Article},
      source={Scopus},
      }

  • Erratum to “Phase-field modeling of crack branching and deflection in heterogeneous media” [Eng. Fract. Mech. 232 (2020) 107004] (Engineering Fracture Mechanics (2020) 232, (S0013794419315474), (10.1016/j.engfracmech.2020.107004))
    • A. C. Hansen-Dörr, F. Dammaß, R. de Borst, M. Kästner
    • Engineering Fracture Mechanics 241, 107449 (2021)
    • DOI   Abstract  

      In Section 2.7, the solution of heterogeneous, one-dimensional phase-field profiles with the intent to improve previous analytical correction approaches was brought into consideration in a personal communication by Keita Yoshioka, Helmholtz Centre for Environmental Research. © 2020

      @ARTICLE{Hansen-Dörr2021,
      author={Hansen-Dörr, A.C. and Dammaß, F. and de Borst, R. and Kästner, M.},
      title={Erratum to “Phase-field modeling of crack branching and deflection in heterogeneous media” [Eng. Fract. Mech. 232 (2020) 107004] (Engineering Fracture Mechanics (2020) 232, (S0013794419315474), (10.1016/j.engfracmech.2020.107004))},
      journal={Engineering Fracture Mechanics},
      year={2021},
      volume={241},
      doi={10.1016/j.engfracmech.2020.107449},
      art_number={107449},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097738647&doi=10.1016%2fj.engfracmech.2020.107449&partnerID=40&md5=a5969e1892eb918aaef6ad1877149234},
      affiliation={Institute of Solid Mechanics, TU Dresden, Dresden, 01062, Germany; University of Sheffield, Department of Civil and Structural Engineering, Mappin Street, Sir Frederick Mappin Building, Sheffield, S1 3JD, United Kingdom; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={In Section 2.7, the solution of heterogeneous, one-dimensional phase-field profiles with the intent to improve previous analytical correction approaches was brought into consideration in a personal communication by Keita Yoshioka, Helmholtz Centre for Environmental Research. © 2020},
      document_type={Erratum},
      source={Scopus},
      }

  • Determining the Diffusion Coefficient of Lithium Insertion Cathodes from GITT measurements: Theoretical Analysis for low Temperatures**
    • T. Schied, A. Nickol, C. Heubner, M. Schneider, A. Michaelis, M. Bobeth, G. Cuniberti
    • ChemPhysChem (2021)
    • DOI   Abstract  

      Accurate knowledge of transport properties of Li-insertion materials in application-relevant temperature ranges is of crucial importance for the targeted optimization of Li-ion batteries (LIBs). Galvanostatic intermittent titration technique (GITT) is a widely applied method to determine Li-ion diffusion coefficients of electrode materials. The well-known calculation formulas based on Weppner’s and Huggins’ approach, imply a square-root time dependence of the potential during a GITT pulse. Charging the electrochemical double layer capacitance at the beginning of a GITT pulse usually takes less than one second. However, at lower temperatures down to −40 °C, the double layer charging time strongly increases due to an increase of the charge transfer resistance. The charging time can become comparable with the pulse duration, impeding the conventional GITT diffusion analysis. We propose a model to describe the potential change during a galvanostatic current pulse, which includes an initial, relatively long-lasting double layer charging, and analyze the accuracy of the lithium diffusion coefficient, derived by using the Weppner-Huggins method within a suitably chosen time interval of the pulse. Effects leading to an inaccurate determination of the diffusion coefficient are discussed and suggestions to improve GITT analyses at low temperature are derived. © 2021 The Authors. ChemPhysChem published by Wiley-VCH GmbH

      @ARTICLE{Schied2021,
      author={Schied, T. and Nickol, A. and Heubner, C. and Schneider, M. and Michaelis, A. and Bobeth, M. and Cuniberti, G.},
      title={Determining the Diffusion Coefficient of Lithium Insertion Cathodes from GITT measurements: Theoretical Analysis for low Temperatures**},
      journal={ChemPhysChem},
      year={2021},
      doi={10.1002/cphc.202001025},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85104242079&doi=10.1002%2fcphc.202001025&partnerID=40&md5=4ca2f07390cb9780f83f335a9025cf8b},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Fraunhofer IKTS Dresden, Winterbergstr. 28, Dresden, 01277, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={Accurate knowledge of transport properties of Li-insertion materials in application-relevant temperature ranges is of crucial importance for the targeted optimization of Li-ion batteries (LIBs). Galvanostatic intermittent titration technique (GITT) is a widely applied method to determine Li-ion diffusion coefficients of electrode materials. The well-known calculation formulas based on Weppner's and Huggins’ approach, imply a square-root time dependence of the potential during a GITT pulse. Charging the electrochemical double layer capacitance at the beginning of a GITT pulse usually takes less than one second. However, at lower temperatures down to −40 °C, the double layer charging time strongly increases due to an increase of the charge transfer resistance. The charging time can become comparable with the pulse duration, impeding the conventional GITT diffusion analysis. We propose a model to describe the potential change during a galvanostatic current pulse, which includes an initial, relatively long-lasting double layer charging, and analyze the accuracy of the lithium diffusion coefficient, derived by using the Weppner-Huggins method within a suitably chosen time interval of the pulse. Effects leading to an inaccurate determination of the diffusion coefficient are discussed and suggestions to improve GITT analyses at low temperature are derived. © 2021 The Authors. ChemPhysChem published by Wiley-VCH GmbH},
      author_keywords={Battery; charge transfer; diffusion coefficient of cathode material; galvanostatic intermittent titration technique; low temperature kinetics},
      document_type={Article},
      source={Scopus},
      }

2020

  • Determination of the entire stent surface area by a new analytical method
    • M. Saqib, R. Bernhardt, M. Kästner, N. Beshchasna, G. Cuniberti, J. Opitz
    • Materials 13, 1-11 , 5633 (2020)
    • DOI   Abstract  

      Stenting is a widely used treatment procedure for coronary artery disease around the world. Stents have a complex geometry, which makes the characterization of their corrosion difficult due to the absence of a mathematical model to calculate the entire stent surface area (ESSA). Therefore, corrosion experiments with stents are mostly based on qualitative analysis. Additionally, the quantitative analysis of corrosion is conducted with simpler samples made of stent material instead of stents, in most cases. At present, several methods are available to calculate the stent outer surface area (SOSA), whereas no model exists for the calculation of the ESSA. This paper presents a novel mathematical model for the calculation of the ESSA using the SOSA as one of the main parameters. The ESSA of seven magnesium alloy stents (MeKo Laser Material Processing GmbH, Sarstedt, Germany) were calculated using the developed model. The calculated SOSA and ESSA for all stents are 33.34% (±0.26%) and 111.86 mm (±0.85 mm), respectively. The model is validated by micro-computed tomography (micro-CT), with a difference of 12.34% (±0.46%). The value of corrosion rates calculated using the ESSA computed with the developed model will be 12.34% (±0.46%) less than that of using ESSA obtained by micro-CT. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

      @ARTICLE{Saqib20201,
      author={Saqib, M. and Bernhardt, R. and Kästner, M. and Beshchasna, N. and Cuniberti, G. and Opitz, J.},
      title={Determination of the entire stent surface area by a new analytical method},
      journal={Materials},
      year={2020},
      volume={13},
      number={24},
      pages={1-11},
      doi={10.3390/ma13245633},
      art_number={5633},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097530492&doi=10.3390%2fma13245633&partnerID=40&md5=0f7b4cc4e6c6eaf7c3e1cdc91130ddde},
      affiliation={Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Maria-Reiche-Strasse 2, Dresden, 01109, Germany; Faculty of Mechanical Science and Engineering, Institute of Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, 01062, Germany; Leibniz Institute of Polymer Research Dresden, Dresden, 01069, Germany; Faculty of Mechanical Science and Engineering, Institute of Solid Mechanics, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={Stenting is a widely used treatment procedure for coronary artery disease around the world. Stents have a complex geometry, which makes the characterization of their corrosion difficult due to the absence of a mathematical model to calculate the entire stent surface area (ESSA). Therefore, corrosion experiments with stents are mostly based on qualitative analysis. Additionally, the quantitative analysis of corrosion is conducted with simpler samples made of stent material instead of stents, in most cases. At present, several methods are available to calculate the stent outer surface area (SOSA), whereas no model exists for the calculation of the ESSA. This paper presents a novel mathematical model for the calculation of the ESSA using the SOSA as one of the main parameters. The ESSA of seven magnesium alloy stents (MeKo Laser Material Processing GmbH, Sarstedt, Germany) were calculated using the developed model. The calculated SOSA and ESSA for all stents are 33.34% (±0.26%) and 111.86 mm (±0.85 mm), respectively. The model is validated by micro-computed tomography (micro-CT), with a difference of 12.34% (±0.46%). The value of corrosion rates calculated using the ESSA computed with the developed model will be 12.34% (±0.46%) less than that of using ESSA obtained by micro-CT. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.},
      author_keywords={Corrosion; Degradation; Mass loss; Micro-CT; Quantitative corrosion test; Stents; Surface area},
      document_type={Article},
      source={Scopus},
      }

  • A simulation method for particle migration in microfluidic spirals with application to small and medium particle concentrations
    • T. Hafemann, S. Tschisgale, J. Fröhlich
    • Physics of Fluids 32, 123303 (2020)
    • DOI   Abstract  

      This paper treats the separation of particles in microchannels relevant to biological and industrial process engineering. To elucidate the mechanisms creating uneven distribution of particles over the cross section, simulations are conducted with the particles being geometrically resolved and coupled to the fluid by an immersed-boundary method. In a first step, the method is validated for particle focusing in straight channels. Beyond validation, new information not previously available is reported for these cases. Next, an efficient approach is presented to simulate the motion of particles in spiral ducts of small curvature by means of a well-controlled set of approximate equations. It is applied here to situations with spherical particles and validated with reference data for inertial migration in curved channels achieving good agreement. The simulation data provide new rich information on the details of the separation process concerning migration time, particle positioning in the cross section, streamwise particle spacing, and velocity field of the continuous phase. For concentrations smaller than 1%, three different focusing modes are observed: single position, two symmetric positions, and periodic trajectories oscillating between two focusing points. Another set of results is obtained with particle concentrations up to 10% in a curved channel. Here, the spatial distribution of particles is determined in a statistical sense and related to the mean flow of the continuous phase. While focusing is reduced with increasing particle concentration, the distribution of particles is found to be still far from uniform up to the investigated concentration level. © 2020 Author(s).

      @ARTICLE{Hafemann2020,
      author={Hafemann, T. and Tschisgale, S. and Fröhlich, J.},
      title={A simulation method for particle migration in microfluidic spirals with application to small and medium particle concentrations},
      journal={Physics of Fluids},
      year={2020},
      volume={32},
      number={12},
      doi={10.1063/5.0024472},
      art_number={123303},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097330589&doi=10.1063%2f5.0024472&partnerID=40&md5=61dbedee403c5d03469dfe549b487633},
      affiliation={Chair of Fluid Mechanics, Tu Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, Tu Dresden, Dresden, 01062, Germany; Institute of Air Handling and Refrigeration, Dresden, 01309, Germany},
      abstract={This paper treats the separation of particles in microchannels relevant to biological and industrial process engineering. To elucidate the mechanisms creating uneven distribution of particles over the cross section, simulations are conducted with the particles being geometrically resolved and coupled to the fluid by an immersed-boundary method. In a first step, the method is validated for particle focusing in straight channels. Beyond validation, new information not previously available is reported for these cases. Next, an efficient approach is presented to simulate the motion of particles in spiral ducts of small curvature by means of a well-controlled set of approximate equations. It is applied here to situations with spherical particles and validated with reference data for inertial migration in curved channels achieving good agreement. The simulation data provide new rich information on the details of the separation process concerning migration time, particle positioning in the cross section, streamwise particle spacing, and velocity field of the continuous phase. For concentrations smaller than 1%, three different focusing modes are observed: single position, two symmetric positions, and periodic trajectories oscillating between two focusing points. Another set of results is obtained with particle concentrations up to 10% in a curved channel. Here, the spatial distribution of particles is determined in a statistical sense and related to the mean flow of the continuous phase. While focusing is reduced with increasing particle concentration, the distribution of particles is found to be still far from uniform up to the investigated concentration level. © 2020 Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • The Weak 3D Topological Insulator Bi12Rh3Sn3I9
    • M. Lê Anh, M. Kaiser, M. P. Ghimire, M. Richter, K. Koepernik, M. Gruschwitz, C. Tegenkamp, T. Doert, M. Ruck
    • Chemistry – A European Journal 26, 15549-15557 (2020)
    • DOI   Abstract  

      Topological insulators (TIs) gained high interest due to their protected electronic surface states that allow dissipation-free electron and information transport. In consequence, TIs are recommended as materials for spintronics and quantum computing. Yet, the number of well-characterized TIs is rather limited. To contribute to this field of research, we focused on new bismuth-based subiodides and recently succeeded in synthesizing a new compound Bi12Rh3Sn3I9, which is structurally closely related to Bi14Rh3I9 – a stable, layered material. In fact, Bi14Rh3I9 is the first experimentally supported weak 3D TI. Both structures are composed of well-defined intermetallic layers of ∞2[(Bi4Rh)3I]2+ with topologically protected electronic edge-states. The fundamental difference between Bi14Rh3I9 and Bi12Rh3Sn3I9 lies in the composition and the arrangement of the anionic spacer. While the intermetallic 2D TI layers in Bi14Rh3I9 are isolated by ∞1[Bi2I8]2− chains, the isoelectronic substitution of bismuth(III) with tin(II) leads to ∞2[Sn3I8]2− layers as anionic spacers. First transport experiments support the 2D character of this material class and revealed metallic conductivity. © 2020 The Authors. Published by Wiley-VCH GmbH

      @ARTICLE{LêAnh202015549,
      author={Lê Anh, M. and Kaiser, M. and Ghimire, M.P. and Richter, M. and Koepernik, K. and Gruschwitz, M. and Tegenkamp, C. and Doert, T. and Ruck, M.},
      title={The Weak 3D Topological Insulator Bi12Rh3Sn3I9},
      journal={Chemistry - A European Journal},
      year={2020},
      volume={26},
      number={67},
      pages={15549-15557},
      doi={10.1002/chem.202001953},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092060259&doi=10.1002%2fchem.202001953&partnerID=40&md5=6f8b24e793798732103914f88a2b51d8},
      affiliation={Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, Dresden, 01062, Germany; Central Department of Physics, Tribhuvan University, Kirtipur, Kathmandu, Nepal; Leibniz IFW Dresden, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Institute of Physics, Technische Universität Chemnitz, Chemnitz, 09126, Germany; Max Planck Institute for Chemical Physics of Solids, Dresden, 01187, Germany},
      abstract={Topological insulators (TIs) gained high interest due to their protected electronic surface states that allow dissipation-free electron and information transport. In consequence, TIs are recommended as materials for spintronics and quantum computing. Yet, the number of well-characterized TIs is rather limited. To contribute to this field of research, we focused on new bismuth-based subiodides and recently succeeded in synthesizing a new compound Bi12Rh3Sn3I9, which is structurally closely related to Bi14Rh3I9 – a stable, layered material. In fact, Bi14Rh3I9 is the first experimentally supported weak 3D TI. Both structures are composed of well-defined intermetallic layers of ∞2[(Bi4Rh)3I]2+ with topologically protected electronic edge-states. The fundamental difference between Bi14Rh3I9 and Bi12Rh3Sn3I9 lies in the composition and the arrangement of the anionic spacer. While the intermetallic 2D TI layers in Bi14Rh3I9 are isolated by ∞1[Bi2I8]2− chains, the isoelectronic substitution of bismuth(III) with tin(II) leads to ∞2[Sn3I8]2− layers as anionic spacers. First transport experiments support the 2D character of this material class and revealed metallic conductivity. © 2020 The Authors. Published by Wiley-VCH GmbH},
      author_keywords={crystal growth; crystal structure; topological band gap; topological insulators; weak topological insulators},
      document_type={Article},
      source={Scopus},
      }

  • Erratum: Field-induced interactions in magneto-active elastomers — A comparison of experiments and simulations (Smart Materials and Structures (2020) 29 (085026) DOI: 10.13039/501100001659)
    • P. Metsch, H. Schmidt, D. Sindersberger, K. A. Kalina, J. Brummund, G. K. Auernhammer, G. J. Monkman, M. Kästner
    • Smart Materials and Structures 29, 119501 (2020)
    • DOI   Abstract  

      (Figure Presented). The authors would like to correct an erroneous picture within the published paper that was accidentally regenerated using wrong data after the revision process. On page 6 in the published paper, figure 6(b) shows wrong results for the two-dimensional simulation (dashed, gray line). The results shown in the picture are in contradiction with the given explanations on the same page and, thus, figure 6(b) should be replaced by the original, correct version that is shown here. © 2020 IOP Publishing Ltd.

      @ARTICLE{Metsch2020,
      author={Metsch, P. and Schmidt, H. and Sindersberger, D. and Kalina, K.A. and Brummund, J. and Auernhammer, G.K. and Monkman, G.J. and Kästner, M.},
      title={Erratum: Field-induced interactions in magneto-active elastomers — A comparison of experiments and simulations (Smart Materials and Structures (2020) 29 (085026) DOI: 10.13039/501100001659)},
      journal={Smart Materials and Structures},
      year={2020},
      volume={29},
      number={11},
      doi={10.1088/1361-665X/abb98b},
      art_number={119501},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095884853&doi=10.1088%2f1361-665X%2fabb98b&partnerID=40&md5=15bd770581b6a66b79b3da28cb9ead18},
      affiliation={Institute of Solid Mechanics, Technische Universität Dresden, Dresden, 01062, Germany; Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany; Mechatronics Research Unit, OTH Regensburg, Regensburg, Germany; Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, Germany},
      abstract={(Figure Presented). The authors would like to correct an erroneous picture within the published paper that was accidentally regenerated using wrong data after the revision process. On page 6 in the published paper, figure 6(b) shows wrong results for the two-dimensional simulation (dashed, gray line). The results shown in the picture are in contradiction with the given explanations on the same page and, thus, figure 6(b) should be replaced by the original, correct version that is shown here. © 2020 IOP Publishing Ltd.},
      document_type={Erratum},
      source={Scopus},
      }

  • Flow-Induced Formation of Thin PEO Fibers in Water and Their Stability after the Strain Release
    • S. Donets, O. Guskova, J. -U. Sommer
    • Journal of Physical Chemistry B 124, 9224-9229 (2020)
    • DOI   Abstract  

      Recently, we have shown that a tensile stress applied to chains of poly(ethylene oxide) (PEO) in water reduces the solubility and leads to phase separation of PEO chains from water with the formation of a two-phase region. In this work, we further elucidate the generic mechanism behind strain-induced phase transitions in aqueous PEO solutions with concentrations of 50-60 wt % by performing all-atom molecular dynamics simulations. In particular, we study the stability of oriented PEO fibers after removing stretching forces. We found that the size of the PEO bundle increased with time, which is associated with the dissolution of PEO chains on the fiber surface due to the reformation of hydrogen bonds between the outer PEO molecules and water. For precise characterization of the fibers, the scattering patterns (small- and wide-angle X-ray spectra) for configurations taken at different relaxation times are calculated. The tendency of the oligomer chains to be peeled off from the surface of the bundle eventually might lead to a complete dissolution of the PEO fiber. We conclude that either entanglement constraints or a quick drying process are necessary to conserve the fiber structure in a quiescent state. The scattering results show that external strain induced a liquid-liquid phase separation first. On long time scales, this can be a precursor for crystallization of the fiber. © 2020 American Chemical Society.

      @ARTICLE{Donets20209224,
      author={Donets, S. and Guskova, O. and Sommer, J.-U.},
      title={Flow-Induced Formation of Thin PEO Fibers in Water and Their Stability after the Strain Release},
      journal={Journal of Physical Chemistry B},
      year={2020},
      volume={124},
      number={41},
      pages={9224-9229},
      doi={10.1021/acs.jpcb.0c05627},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85093539138&doi=10.1021%2facs.jpcb.0c05627&partnerID=40&md5=e0e866f846ac96917c6b0ca79a8e97d9},
      affiliation={Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Institute of Theoretical Physics, Technische Universität Dresden, Zellescher Weg 17, Dresden, 01069, Germany},
      abstract={Recently, we have shown that a tensile stress applied to chains of poly(ethylene oxide) (PEO) in water reduces the solubility and leads to phase separation of PEO chains from water with the formation of a two-phase region. In this work, we further elucidate the generic mechanism behind strain-induced phase transitions in aqueous PEO solutions with concentrations of 50-60 wt % by performing all-atom molecular dynamics simulations. In particular, we study the stability of oriented PEO fibers after removing stretching forces. We found that the size of the PEO bundle increased with time, which is associated with the dissolution of PEO chains on the fiber surface due to the reformation of hydrogen bonds between the outer PEO molecules and water. For precise characterization of the fibers, the scattering patterns (small- and wide-angle X-ray spectra) for configurations taken at different relaxation times are calculated. The tendency of the oligomer chains to be peeled off from the surface of the bundle eventually might lead to a complete dissolution of the PEO fiber. We conclude that either entanglement constraints or a quick drying process are necessary to conserve the fiber structure in a quiescent state. The scattering results show that external strain induced a liquid-liquid phase separation first. On long time scales, this can be a precursor for crystallization of the fiber. © 2020 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Role of Exchange Interactions in the Magnetic Response and Intermolecular Recognition of Chiral Molecules
    • A. Dianat, R. Gutierrez, H. Alpern, V. Mujica, A. Ziv, S. Yochelis, O. Millo, Y. Paltiel, G. Cuniberti
    • Nano Letters 20, 7077-7086 (2020)
    • DOI   Abstract  

      The physical origin of the so-called chirality-induced spin selectivity (CISS) effect has puzzled experimental and theoretical researchers over the past few years. Early experiments were interpreted in terms of unconventional spin-orbit interactions mediated by the helical geometry. However, more recent experimental studies have clearly revealed that electronic exchange interactions also play a key role in the magnetic response of chiral molecules in singlet states. In this investigation, we use spin-polarized closed-shell density functional theory calculations to address the influence of exchange contributions to the interaction between helical molecules as well as of helical molecules with magnetized substrates. We show that exchange effects result in differences in the interaction properties with magnetized surfaces, shedding light into the possible origin of two recent important experimental results: enantiomer separation and magnetic exchange force microscopy with AFM tips functionalized with helical peptides. Copyright © 2020 American Chemical Society.

      @ARTICLE{Dianat20207077,
      author={Dianat, A. and Gutierrez, R. and Alpern, H. and Mujica, V. and Ziv, A. and Yochelis, S. and Millo, O. and Paltiel, Y. and Cuniberti, G.},
      title={Role of Exchange Interactions in the Magnetic Response and Intermolecular Recognition of Chiral Molecules},
      journal={Nano Letters},
      year={2020},
      volume={20},
      number={10},
      pages={7077-7086},
      doi={10.1021/acs.nanolett.0c02216},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092944916&doi=10.1021%2facs.nanolett.0c02216&partnerID=40&md5=5276dd9b4122504d51c64b1000e7bff5},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Tu Dresden, Dresden, 01062, Germany; Applied Physics Department, Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem, 9190401, Israel; Racah Institute of Physics, Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem, 9190401, Israel; School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, United States; Ikerbasque Foundation and Donostia International Physics Center (DIPC), Manuel de Lardizabal Pasealekua 4, Donostia, Euskadi 20018, Spain; Applied Physics Department, Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem, 9190401, Israel; Dresden Center for Computational Materials Science (DCMS), Tu Dresden, Dresden, 01062, Germany},
      abstract={The physical origin of the so-called chirality-induced spin selectivity (CISS) effect has puzzled experimental and theoretical researchers over the past few years. Early experiments were interpreted in terms of unconventional spin-orbit interactions mediated by the helical geometry. However, more recent experimental studies have clearly revealed that electronic exchange interactions also play a key role in the magnetic response of chiral molecules in singlet states. In this investigation, we use spin-polarized closed-shell density functional theory calculations to address the influence of exchange contributions to the interaction between helical molecules as well as of helical molecules with magnetized substrates. We show that exchange effects result in differences in the interaction properties with magnetized surfaces, shedding light into the possible origin of two recent important experimental results: enantiomer separation and magnetic exchange force microscopy with AFM tips functionalized with helical peptides. Copyright © 2020 American Chemical Society.},
      author_keywords={broken symmetry; CISS effect; Density-Functional Theory; Exchange Effects; Helical Molecules},
      document_type={Article},
      source={Scopus},
      }

  • Interactions of long-chain polyamines with silica studied by molecular dynamics simulations and solid-state NMR spectroscopy
    • E. Brunner, G. Cuniberti, M. Montagna, S. I. Brückner, A. Dianat, R. Gutierrez, F. Daus, A. Geyer
    • Langmuir 36, 11600-11609 (2020)
    • DOI   Abstract  

      The investigation of molecular interactions between silica phases and organic components is crucial for elucidating the main steps involved in the biosilica mineralization process. In this respect, the structural characterization of the organic/ inorganic interface is particularly useful for a deeper understanding of the dominant mechanisms of biomineralization. In this work, we have investigated the interaction of selectively 13C- and 15N-labeled atoms of organic long-chain polyamines (LCPAs) with 29Si-labeled atoms of a silica layer at the molecular level. In particular, silica/ LCPA nanocomposites were analyzed by solid-state NMR spectroscopy in combination with all-atom molecular dynamics simulations. Solid-state NMR experiments allow the determination of 29Si-15N and 29Si-13C internuclear distances, providing the parameters for direct verification of atomistic simulations. Our results elucidate the relevant molecular conformations as well as the nature of the interaction between the LCPA and a silica substrate. Specifically, distances and second moments suggest a picture compatible with (i) LCPA completely embedded in the silica phase and (ii) the charged amino groups located in close vicinity of silanol groups. © 2020 American Chemical Society.

      @ARTICLE{Brunner202011600,
      author={Brunner, E. and Cuniberti, G. and Montagna, M. and Brückner, S.I. and Dianat, A. and Gutierrez, R. and Daus, F. and Geyer, A.},
      title={Interactions of long-chain polyamines with silica studied by molecular dynamics simulations and solid-state NMR spectroscopy},
      journal={Langmuir},
      year={2020},
      volume={36},
      number={39},
      pages={11600-11609},
      doi={10.1021/acs.langmuir.0c02157},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092682553&doi=10.1021%2facs.langmuir.0c02157&partnerID=40&md5=64549b4a74d42301e33ea220e8174e91},
      affiliation={Faculty of Chemistry and Food Chemistry, Tu Dresden, Dresden, 01062, Germany; Institute for Materials Science, Max Bergmann Center of Biomaterials, Tu Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, Tu Dresden, Dresden, 01062, Germany; Department of Chemistry, Philipps-University Marburg, Marburg, 35032, Germany},
      abstract={The investigation of molecular interactions between silica phases and organic components is crucial for elucidating the main steps involved in the biosilica mineralization process. In this respect, the structural characterization of the organic/ inorganic interface is particularly useful for a deeper understanding of the dominant mechanisms of biomineralization. In this work, we have investigated the interaction of selectively 13C- and 15N-labeled atoms of organic long-chain polyamines (LCPAs) with 29Si-labeled atoms of a silica layer at the molecular level. In particular, silica/ LCPA nanocomposites were analyzed by solid-state NMR spectroscopy in combination with all-atom molecular dynamics simulations. Solid-state NMR experiments allow the determination of 29Si-15N and 29Si-13C internuclear distances, providing the parameters for direct verification of atomistic simulations. Our results elucidate the relevant molecular conformations as well as the nature of the interaction between the LCPA and a silica substrate. Specifically, distances and second moments suggest a picture compatible with (i) LCPA completely embedded in the silica phase and (ii) the charged amino groups located in close vicinity of silanol groups. © 2020 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Sensitivity to strains and defects for manipulating the conductivity of graphene
    • I. Sahalianov, T. M. Radchenko, V. A. Tatarenko, G. Cuniberti
    • EPL 132, 48002 (2020)
    • DOI   Abstract  

      Implementing the quantum-mechanical Kubo-Greenwood formalism for the numerical calculation of dc conductivity, we demonstrate that the electron transport properties of a graphene layer can be tailored through the combined effect of defects (point and line scatterers) and strains (uniaxial tension and shear), which are commonly present in a graphene sample due to the features of its growth procedure and when the sample is used in devices. Motivated by two experimental works (He X. et al. Appl. Phys. Lett., 104 (2014) 243108; 105 (2014) 083108), where authors did not observe the transport gap even at large (22.5% of tensile and 16.7% of shear) deformations, we explain possible reasons, emphasizing on graphene’s strain and defect sensing. The strain- and defect-induced electron-hole asymmetry and anisotropy of conductivity, and its nonmonotony as a function of deformation suggest perspectives for the strain-defect engineering of electrotransport properties of graphene and related 2D materials. Copyright © 2020 EPLA.

      @ARTICLE{Sahalianov2020,
      author={Sahalianov, I.Yu. and Radchenko, T.M. and Tatarenko, V.A. and Cuniberti, G.},
      title={Sensitivity to strains and defects for manipulating the conductivity of graphene},
      journal={EPL},
      year={2020},
      volume={132},
      number={4},
      doi={10.1209/0295-5075/132/48002},
      art_number={48002},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85099830534&doi=10.1209%2f0295-5075%2f132%2f48002&partnerID=40&md5=c8b76d43bc428ffcf083bf9ad5c53ca7},
      affiliation={Linköping University, Norrköping, 60174, Sweden; G. V. Kurdyumov Institute for Metal Physics of the NAS of Ukraine, Kyiv, 03142, Ukraine; Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany},
      abstract={Implementing the quantum-mechanical Kubo-Greenwood formalism for the numerical calculation of dc conductivity, we demonstrate that the electron transport properties of a graphene layer can be tailored through the combined effect of defects (point and line scatterers) and strains (uniaxial tension and shear), which are commonly present in a graphene sample due to the features of its growth procedure and when the sample is used in devices. Motivated by two experimental works (He X. et al. Appl. Phys. Lett., 104 (2014) 243108; 105 (2014) 083108), where authors did not observe the transport gap even at large (22.5% of tensile and 16.7% of shear) deformations, we explain possible reasons, emphasizing on graphene's strain and defect sensing. The strain- and defect-induced electron-hole asymmetry and anisotropy of conductivity, and its nonmonotony as a function of deformation suggest perspectives for the strain-defect engineering of electrotransport properties of graphene and related 2D materials. Copyright © 2020 EPLA.},
      document_type={Article},
      source={Scopus},
      }

  • Hyperuniform monocrystalline structures by spinodal solid-state dewetting
    • M. Salvalaglio, M. Bouabdellaoui, M. Bollani, A. Benali, L. Favre, J. -B. Claude, J. Wenger, P. De Anna, F. Intonti, A. Voigt, M. Abbarchi
    • Physical Review Letters 125, 126101 (2020)
    • DOI   Abstract  

      Materials featuring anomalous suppression of density fluctuations over large length scales are emerging systems known as disordered hyperuniform. The underlying hidden order renders them appealing for several applications, such as light management and topologically protected electronic states. These applications require scalable fabrication, which is hard to achieve with available top-down approaches. Theoretically, it is known that spinodal decomposition can lead to disordered hyperuniform architectures. Spontaneous formation of stable patterns could thus be a viable path for the bottom-up fabrication of these materials. Here, we show that monocrystalline semiconductor-based structures, in particular Si1-xGex layers deposited on silicon-on-insulator substrates, can undergo spinodal solid-state dewetting featuring correlated disorder with an effective hyperuniform character. Nano- to micrometric sized structures targeting specific morphologies and hyperuniform character can be obtained, proving the generality of the approach and paving the way for technological applications of disordered hyperuniform metamaterials. Phase-field simulations explain the underlying nonlinear dynamics and the physical origin of the emerging patterns. © 2020 American Physical Society.

      @ARTICLE{Salvalaglio2020,
      author={Salvalaglio, M. and Bouabdellaoui, M. and Bollani, M. and Benali, A. and Favre, L. and Claude, J.-B. and Wenger, J. and De Anna, P. and Intonti, F. and Voigt, A. and Abbarchi, M.},
      title={Hyperuniform monocrystalline structures by spinodal solid-state dewetting},
      journal={Physical Review Letters},
      year={2020},
      volume={125},
      number={12},
      doi={10.1103/PhysRevLett.125.126101},
      art_number={126101},
      note={cited By 2},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092427244&doi=10.1103%2fPhysRevLett.125.126101&partnerID=40&md5=3431987fa642bf5f2d02d7530d42c695},
      affiliation={Institute of Scientific Computing, Tu Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Tu Dresden, Dresden, 01062, Germany; Aix Marseille Univ, Université de Toulon, Cnrs, IM2NP, Marseille, 13397, France; Istituto di Fotonica e Nanotecnologie-Consiglio Nazionale Delle Ricerche, Laboratory for Nanostructure Epitaxy and Spintronics on Silicon, Via Anzani 42, Como, 22100, Italy; Aix Marseille Université, Cnrs, Centrale Marseille, Institut Fresnel, Marseille, 13013, France; Institut des Sciences de la Terre, University of Lausanne, Lausanne, 1015, Switzerland; Lens, University of Florence, Sesto Fiorentino, 50019, Italy},
      abstract={Materials featuring anomalous suppression of density fluctuations over large length scales are emerging systems known as disordered hyperuniform. The underlying hidden order renders them appealing for several applications, such as light management and topologically protected electronic states. These applications require scalable fabrication, which is hard to achieve with available top-down approaches. Theoretically, it is known that spinodal decomposition can lead to disordered hyperuniform architectures. Spontaneous formation of stable patterns could thus be a viable path for the bottom-up fabrication of these materials. Here, we show that monocrystalline semiconductor-based structures, in particular Si1-xGex layers deposited on silicon-on-insulator substrates, can undergo spinodal solid-state dewetting featuring correlated disorder with an effective hyperuniform character. Nano- to micrometric sized structures targeting specific morphologies and hyperuniform character can be obtained, proving the generality of the approach and paving the way for technological applications of disordered hyperuniform metamaterials. Phase-field simulations explain the underlying nonlinear dynamics and the physical origin of the emerging patterns. © 2020 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Universal Limit for Air-Stable Molecular n-Doping in Organic Semiconductors
    • M. Schwarze, M. L. Tietze, F. Ortmann, H. Kleemann, K. Leo
    • ACS Applied Materials and Interfaces 12, 40566-40571 (2020)
    • DOI   Abstract  

      The air sensitivity of n-doped layers is crucial for the long-term stability of organic electronic devices. Although several air-stable and highly efficient n-dopants have been developed, the reason for the varying air sensitivity between different n-doped layers, in which the n-dopant molecules are dispersed, is not fully understood. In contrast to previous studies that compared the air stability of doped films with the energy levels of neat host or dopant layers, we trace back the varying degree of air sensitivity to the energy levels of integer charge transfer states (ICTCs) formed by host anions and dopant cations. Our data indicate a universal limit for the ionization energy of ICTCs above which the n-doped semiconductors are air-stable. © 2020 American Chemical Society.

      @ARTICLE{Schwarze202040566,
      author={Schwarze, M. and Tietze, M.L. and Ortmann, F. and Kleemann, H. and Leo, K.},
      title={Universal Limit for Air-Stable Molecular n-Doping in Organic Semiconductors},
      journal={ACS Applied Materials and Interfaces},
      year={2020},
      volume={12},
      number={36},
      pages={40566-40571},
      doi={10.1021/acsami.0c04380},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090870344&doi=10.1021%2facsami.0c04380&partnerID=40&md5=719ea2a9bea7159ee921359afd94a68c},
      affiliation={Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP), Technische Universität Dresden, Dresden, 01069, Germany; Center for Advancing Electronics Dresden, Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01069, Germany},
      abstract={The air sensitivity of n-doped layers is crucial for the long-term stability of organic electronic devices. Although several air-stable and highly efficient n-dopants have been developed, the reason for the varying air sensitivity between different n-doped layers, in which the n-dopant molecules are dispersed, is not fully understood. In contrast to previous studies that compared the air stability of doped films with the energy levels of neat host or dopant layers, we trace back the varying degree of air sensitivity to the energy levels of integer charge transfer states (ICTCs) formed by host anions and dopant cations. Our data indicate a universal limit for the ionization energy of ICTCs above which the n-doped semiconductors are air-stable. © 2020 American Chemical Society.},
      author_keywords={air-stable n-doping; electrical conductivity; electron trap; Fermi level; integer charge transfer complex; molecular doping; photoelectron spectroscopy; universal limit},
      document_type={Article},
      source={Scopus},
      }

  • Nanocytometer for smart analysis of peripheral blood and acute myeloid leukemia: A pilot study
    • J. Schütt, D. I. Sandoval Bojorquez, E. Avitabile, E. S. Oliveros Mata, G. Milyukov, J. Colditz, L. G. Delogu, M. Rauner, A. Feldmann, S. Koristka, J. M. Middeke, K. Sockel, J. Fassbender, M. Bachmann, M. Bornhäuser, G. Cuniberti, L. Baraban
    • Nano Letters 20, 6572-6581 (2020)
    • DOI   Abstract  

      We realize an ultracompact nanocytometer for real-time impedimetric detection and classification of subpopulations of living cells. Nanoscopic nanowires in a microfluidic channel act as nanocapacitors and measure in real time the change of the amplitude and phase of the output voltage and, thus, the electrical properties of living cells. We perform the cell classification in the human peripheral blood (PBMC) and demonstrate for the first time the possibility to discriminate monocytes and subpopulations of lymphocytes in a label-free format. Further, we demonstrate that the PBMC of acute myeloid leukemia and healthy samples grant the label free identification of the disease. Using the algorithm based on machine learning, we generated specific data patterns to discriminate healthy donors and leukemia patients. Such a solution has the potential to improve the traditional diagnostics approaches with respect to the overall cost and time effort, in a label-free format, and restrictions of the complex data analysis. © 2020 American Chemical Society.

      @ARTICLE{Schütt20206572,
      author={Schütt, J. and Sandoval Bojorquez, D.I. and Avitabile, E. and Oliveros Mata, E.S. and Milyukov, G. and Colditz, J. and Delogu, L.G. and Rauner, M. and Feldmann, A. and Koristka, S. and Middeke, J.M. and Sockel, K. and Fassbender, J. and Bachmann, M. and Bornhäuser, M. and Cuniberti, G. and Baraban, L.},
      title={Nanocytometer for smart analysis of peripheral blood and acute myeloid leukemia: A pilot study},
      journal={Nano Letters},
      year={2020},
      volume={20},
      number={9},
      pages={6572-6581},
      doi={10.1021/acs.nanolett.0c02300},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090613693&doi=10.1021%2facs.nanolett.0c02300&partnerID=40&md5=82f2185f39a0003f96d440c6b7ae8877},
      affiliation={Max Bergmann Center of Biomaterials, Institute for Materials Science, Dresden University of Technology, Budapesterstrasse 27, Dresden, 01069, Germany; Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf E.V., Bautzner Landstrasse 400, Dresden, 01328, Germany; Department of Chemistry and Pharmacy, University of Sassari, via muroni 23, Sassari, 07100, Italy; Samsung R and D Institute Russia (SRR), Moscow, 127018, Russian Federation; Department of Biomedical Sciences, University of Padua, via Ugo bassi 58, Padua, 35122, Italy; Medizinische Klinik und Poliklinik i, Universitätsklinikum Carl Gustav Carus Dresden, Dresden, 01307, Germany; Medizinische Klinik und Poliklinik III, Universitätsklinikum Carl Gustav Carus Dresden, Dresden, 01307, Germany; Center for Advancing Electronics Dresden (Cfaed), Technische Universität Dresden, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf E.V., Bautzner Landstrasse 400, Dresden, 01328, Germany; Else Kröner-Fresenius Center for Digital Health (EKFZ), Technische Universität Dresden (TU Dresden), Dresden, Germany},
      abstract={We realize an ultracompact nanocytometer for real-time impedimetric detection and classification of subpopulations of living cells. Nanoscopic nanowires in a microfluidic channel act as nanocapacitors and measure in real time the change of the amplitude and phase of the output voltage and, thus, the electrical properties of living cells. We perform the cell classification in the human peripheral blood (PBMC) and demonstrate for the first time the possibility to discriminate monocytes and subpopulations of lymphocytes in a label-free format. Further, we demonstrate that the PBMC of acute myeloid leukemia and healthy samples grant the label free identification of the disease. Using the algorithm based on machine learning, we generated specific data patterns to discriminate healthy donors and leukemia patients. Such a solution has the potential to improve the traditional diagnostics approaches with respect to the overall cost and time effort, in a label-free format, and restrictions of the complex data analysis. © 2020 American Chemical Society.},
      author_keywords={acute myeloid leukemia (AML); impedance cytometer; machine learning for data treatment; nanosensor; PBMCs; POC diagnostics},
      document_type={Article},
      source={Scopus},
      }

  • Understanding the UV luminescence of zinc germanate: The role of native defects
    • J. Dolado, R. Martínez-Casado, P. Hidalgo, R. Gutierrez, A. Dianat, G. Cuniberti, F. Domínguez-Adame, E. Díaz, B. Méndez
    • Acta Materialia 196, 626-634 (2020)
    • DOI   Abstract  

      Achieving efficient and stable ultraviolet emission is a challenging goal in optoelectronic devices. Herein, we investigate the UV luminescence of zinc germanate Zn2GeO4 microwires by means of photoluminescence measurements as a function of temperature and excitation conditions. The emitted UV light is composed of two bands (a broad one and a narrow one) associated with the native defects structure. In addition, with the aid of density functional theory (DFT) calculations, the energy positions of the electronic levels related to native defects in Zn2GeO4 have been calculated. In particular, our results support that zinc interstitials are the responsible for the narrow UV band, which is, in turn, split into two components with different temperature dependence behaviour. The origin of the two components is explained on the basis of the particular location of Zni in the lattice and agrees with DFT calculations. Furthermore, a kinetic luminescence model is proposed to ascertain the temperature evolution of this UV emission. These results pave the way to exploit defect engineering in achieving functional optoelectronic devices to operate in the UV region. © 2020 Acta Materialia Inc.

      @ARTICLE{Dolado2020626,
      author={Dolado, J. and Martínez-Casado, R. and Hidalgo, P. and Gutierrez, R. and Dianat, A. and Cuniberti, G. and Domínguez-Adame, F. and Díaz, E. and Méndez, B.},
      title={Understanding the UV luminescence of zinc germanate: The role of native defects},
      journal={Acta Materialia},
      year={2020},
      volume={196},
      pages={626-634},
      doi={10.1016/j.actamat.2020.07.009},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087993125&doi=10.1016%2fj.actamat.2020.07.009&partnerID=40&md5=6a83cc7a1baa001b356c5a0bd1d238e9},
      affiliation={Departamento de Física de Materiales, Universidad Complutense de Madrid, Madrid, E-28040, Spain; Institute for Materials Science, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Achieving efficient and stable ultraviolet emission is a challenging goal in optoelectronic devices. Herein, we investigate the UV luminescence of zinc germanate Zn2GeO4 microwires by means of photoluminescence measurements as a function of temperature and excitation conditions. The emitted UV light is composed of two bands (a broad one and a narrow one) associated with the native defects structure. In addition, with the aid of density functional theory (DFT) calculations, the energy positions of the electronic levels related to native defects in Zn2GeO4 have been calculated. In particular, our results support that zinc interstitials are the responsible for the narrow UV band, which is, in turn, split into two components with different temperature dependence behaviour. The origin of the two components is explained on the basis of the particular location of Zni in the lattice and agrees with DFT calculations. Furthermore, a kinetic luminescence model is proposed to ascertain the temperature evolution of this UV emission. These results pave the way to exploit defect engineering in achieving functional optoelectronic devices to operate in the UV region. © 2020 Acta Materialia Inc.},
      author_keywords={Density functional theory; Native defects; Photoluminescence; Ultraviolet emission; Zinc germanate},
      document_type={Article},
      source={Scopus},
      }

  • Field-induced interactions in magneto-active elastomers – A comparison of experiments and simulations
    • P. Metsch, H. Schmidt, D. Sindersberger, K. A Kalina, J. Brummund, G. K Auernhammer, G. J. Monkman, M. Kästner
    • Smart Materials and Structures 29, 085026 (2020)
    • DOI   Abstract  

      In this contribution, field-induced interactions of magnetizable particles embedded into a soft elastomer matrix are analyzed with regard to the resulting mechanical deformations. By comparing experiments for two-, three- and four-particle systems with the results of finite element simulations, a fully coupled continuum model for magneto-active elastomers is validated with the help of real data for the first time. The model under consideration permits the investigation of magneto-active elastomers with arbitrary particle distances, shapes and volume fractions as well as magnetic and mechanical properties of the individual constituents. It thus represents a basis for future studies on more complex, realistic systems. Our results show a very good agreement between experiments and numerical simulations – the deformation behavior of all systems is captured by the model qualitatively as well as quantitatively. Within a sensitivity analysis, the influence of the initial particle positions on the systems‘ response is examined. Furthermore, a comparison of the full three-dimensional model with the often used, simplified two-dimensional approach shows the typical overestimation of resulting interactions in magneto-active elastomers. © 2020 The Author(s). Published by IOP Publishing Ltd.

      @ARTICLE{Metsch2020,
      author={Metsch, P. and Schmidt, H. and Sindersberger, D. and A Kalina, K. and Brummund, J. and K Auernhammer, G. and Monkman, G.J. and Kästner, M.},
      title={Field-induced interactions in magneto-active elastomers - A comparison of experiments and simulations},
      journal={Smart Materials and Structures},
      year={2020},
      volume={29},
      number={8},
      doi={10.1088/1361-665X/ab92dc},
      art_number={085026},
      note={cited By 6},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089585983&doi=10.1088%2f1361-665X%2fab92dc&partnerID=40&md5=32b0144d5adaec5ef94ecbe186929794},
      affiliation={Institute of Solid Mechanics, Technische Universität Dresden, Dresden, 01062, Germany; Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany; Mechatronics Research Unit, OTH Regensburg, Regensburg, Germany; Leibniz-Institut für Polymerforschung Dresden E.V., Hohe Straße 6, 01069 Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, Germany},
      abstract={In this contribution, field-induced interactions of magnetizable particles embedded into a soft elastomer matrix are analyzed with regard to the resulting mechanical deformations. By comparing experiments for two-, three- and four-particle systems with the results of finite element simulations, a fully coupled continuum model for magneto-active elastomers is validated with the help of real data for the first time. The model under consideration permits the investigation of magneto-active elastomers with arbitrary particle distances, shapes and volume fractions as well as magnetic and mechanical properties of the individual constituents. It thus represents a basis for future studies on more complex, realistic systems. Our results show a very good agreement between experiments and numerical simulations - the deformation behavior of all systems is captured by the model qualitatively as well as quantitatively. Within a sensitivity analysis, the influence of the initial particle positions on the systems' response is examined. Furthermore, a comparison of the full three-dimensional model with the often used, simplified two-dimensional approach shows the typical overestimation of resulting interactions in magneto-active elastomers. © 2020 The Author(s). Published by IOP Publishing Ltd.},
      author_keywords={field-induced interactions; magneto-active elastomers; nonlinear finite element-method},
      document_type={Article},
      source={Scopus},
      }

  • Discovery, Crystal Growth, and Characterization of Garnet Eu2PbSb2Zn3O12
    • R. Morrow, M. I. Sturza, R. Ray, C. Himcinschi, J. Kern, P. Schlender, M. Richter, S. Wurmehl, B. Büchner
    • European Journal of Inorganic Chemistry 2020, 2512-2520 (2020)
    • DOI   Abstract  

      Single crystal specimens of previously unknown garnet Eu2PbSb2Zn3O12 were grown in a reactive PbO:PbF2 flux medium. The crystals were characterized by a combination of X-ray crystallography, magnetization measurements, and the optical techniques of Raman, photoluminescence, and UV/Vis spectroscopy. The material exhibits Van Vleck paramagnetism associated with the J = 0 state of Eu3+, which was possible to accurately fit to a theoretical model. Band structure calculations were performed and compared to the experimental band gap of 1.98 eV. The crystals demonstrate photoluminescence associated with the 4f 6 configuration of the Eu3+ ions sitting at the distorted 8-coordinate garnet A site. The title compound represents a unique quinary contribution to a relatively unexplored area of rare earth bearing garnet crystal chemistry. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

      @ARTICLE{Morrow20202512,
      author={Morrow, R. and Sturza, M.I. and Ray, R. and Himcinschi, C. and Kern, J. and Schlender, P. and Richter, M. and Wurmehl, S. and Büchner, B.},
      title={Discovery, Crystal Growth, and Characterization of Garnet Eu2PbSb2Zn3O12},
      journal={European Journal of Inorganic Chemistry},
      year={2020},
      volume={2020},
      number={26},
      pages={2512-2520},
      doi={10.1002/ejic.202000271},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087171097&doi=10.1002%2fejic.202000271&partnerID=40&md5=871fb34e5836968fe3ee1ee7495913b4},
      affiliation={Leibniz Institute for Solid State and Materials Research Dresden IFW, Helmholtzstr. 20, Dresden, D-01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, D-01062, Germany; Institute of Theoretical Physics, TU Bergakademie Freiberg, Freiberg, D-09599, Germany; Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, Dresden, D-01062, Germany; Institut für Festkörperphysik, Technische Universität Dresden, Dresden, D-01069, Germany},
      abstract={Single crystal specimens of previously unknown garnet Eu2PbSb2Zn3O12 were grown in a reactive PbO:PbF2 flux medium. The crystals were characterized by a combination of X-ray crystallography, magnetization measurements, and the optical techniques of Raman, photoluminescence, and UV/Vis spectroscopy. The material exhibits Van Vleck paramagnetism associated with the J = 0 state of Eu3+, which was possible to accurately fit to a theoretical model. Band structure calculations were performed and compared to the experimental band gap of 1.98 eV. The crystals demonstrate photoluminescence associated with the 4f 6 configuration of the Eu3+ ions sitting at the distorted 8-coordinate garnet A site. The title compound represents a unique quinary contribution to a relatively unexplored area of rare earth bearing garnet crystal chemistry. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.},
      author_keywords={Crystal growth; Garnet; Magnetic properties; Photoluminescence; Solid State Chemistry},
      document_type={Article},
      source={Scopus},
      }

  • A macroscopic model for magnetorheological elastomers based on microscopic simulations
    • K. A. Kalina, P. Metsch, J. Brummund, M. Kästner
    • International Journal of Solids and Structures 193-194, 200-212 (2020)
    • DOI   Abstract  

      In this contribution, we present a novel proceeding for the development of a suitable macroscopic model for magneto-active composites. Based on a general continuum formulation of the coupled magneto-mechanical boundary value problem, valid for finite strains, a microscopic modeling approach is applied within a computational homogenization scheme. The calculated effective magneto-mechanical response of the composite system is used to identify the parameters of the macroscopic model. The merit of this strategy is the identification of the model fitting parameters independent of any macroscopic sample geometry. Furthermore, it facilitates the generation of large databases consisting of multiple load cases without performing expensive experiments. This strategy is applied for several microstructures with random particle distributions, where two-dimensional plane strain problems in the linear magnetization regime are considered for now. Finally, the magnetostrictive behavior of a macroscopic magneto-rheological elastomer sample is simulated for different sample geometries and underlying microstructures. © 2020

      @ARTICLE{Kalina2020200,
      author={Kalina, K.A. and Metsch, P. and Brummund, J. and Kästner, M.},
      title={A macroscopic model for magnetorheological elastomers based on microscopic simulations},
      journal={International Journal of Solids and Structures},
      year={2020},
      volume={193-194},
      pages={200-212},
      doi={10.1016/j.ijsolstr.2020.02.028},
      note={cited By 8},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079865472&doi=10.1016%2fj.ijsolstr.2020.02.028&partnerID=40&md5=5535f2086ae130458ed33aeb1aef70f1},
      affiliation={Institute of Solid Mechanics, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={In this contribution, we present a novel proceeding for the development of a suitable macroscopic model for magneto-active composites. Based on a general continuum formulation of the coupled magneto-mechanical boundary value problem, valid for finite strains, a microscopic modeling approach is applied within a computational homogenization scheme. The calculated effective magneto-mechanical response of the composite system is used to identify the parameters of the macroscopic model. The merit of this strategy is the identification of the model fitting parameters independent of any macroscopic sample geometry. Furthermore, it facilitates the generation of large databases consisting of multiple load cases without performing expensive experiments. This strategy is applied for several microstructures with random particle distributions, where two-dimensional plane strain problems in the linear magnetization regime are considered for now. Finally, the magnetostrictive behavior of a macroscopic magneto-rheological elastomer sample is simulated for different sample geometries and underlying microstructures. © 2020},
      author_keywords={Macro-model; Magneto-mechanical coupling; Magnetorheological elastomers; Parameter identification},
      document_type={Article},
      source={Scopus},
      }

  • First-principles calculation of shift current in chalcopyrite semiconductor ZnSnP2
    • B. Sadhukhan, Y. Zhang, R. Ray, J. Van Den Brink
    • Physical Review Materials 4, 064602 (2020)
    • DOI   Abstract  

      The bulk photovoltaic effect generates intrinsic photocurrents in materials without inversion symmetry. Shift current is one of the bulk photovoltaic phenomena related to the Berry phase of the constituting electronic bands: photoexcited carriers coherently shift in real space due to the difference in the Berry connection between the valence and conduction bands. Ferroelectric semiconductors and Weyl semimetals are known to exhibit such nonlinear optical phenomena. Here we consider the chalcopyrite semiconductor ZnSnP2, which lacks inversion symmetry, and calculate the shift-current conductivity. We find that the magnitude of the shift current is comparable to the recently measured values on other ferroelectric semiconductors and an order of magnitude larger than bismuth ferrite. The peak response for both optical and shift-current conductivity, which mainly comes from P-3p and Sn-5p orbitals, is several eV above the band gap. © 2020 American Physical Society.

      @ARTICLE{Sadhukhan2020,
      author={Sadhukhan, B. and Zhang, Y. and Ray, R. and Van Den Brink, J.},
      title={First-principles calculation of shift current in chalcopyrite semiconductor ZnSnP2},
      journal={Physical Review Materials},
      year={2020},
      volume={4},
      number={6},
      doi={10.1103/PhysRevMaterials.4.064602},
      art_number={064602},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088555947&doi=10.1103%2fPhysRevMaterials.4.064602&partnerID=40&md5=ca0d690022a75dc141859bb33a6c6e51},
      affiliation={Leibniz Institute for Solid State and Materials Research IFW Dresden, Helmholtzstrasse 20, Dresden, 01069, Germany; Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Max Planck Institute for Chemical Physics of Solids, Dresden, 01187, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, D-01062, Germany},
      abstract={The bulk photovoltaic effect generates intrinsic photocurrents in materials without inversion symmetry. Shift current is one of the bulk photovoltaic phenomena related to the Berry phase of the constituting electronic bands: photoexcited carriers coherently shift in real space due to the difference in the Berry connection between the valence and conduction bands. Ferroelectric semiconductors and Weyl semimetals are known to exhibit such nonlinear optical phenomena. Here we consider the chalcopyrite semiconductor ZnSnP2, which lacks inversion symmetry, and calculate the shift-current conductivity. We find that the magnitude of the shift current is comparable to the recently measured values on other ferroelectric semiconductors and an order of magnitude larger than bismuth ferrite. The peak response for both optical and shift-current conductivity, which mainly comes from P-3p and Sn-5p orbitals, is several eV above the band gap. © 2020 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Towards synthetic neural networks: Can artificial electrochemical neurons be coupled with artificial memristive synapses?
    • E. Wlaźlak, D. Przyczyna, R. Gutierrez, G. Cuniberti, K. Szaciłowski
    • Japanese Journal of Applied Physics 59, SI0801 (2020)
    • DOI   Abstract  

      The enormous amount of data generated nowadays worldwide is increasingly triggering the search for unconventional and more efficient ways of processing and classifying information, eventually able to transcend the conventional von Neumann-Turing computational central dogma. It is, therefore, greatly appealing to draw inspiration from less conventional but computationally more powerful systems such as the neural architecture of the human brain. This neuromorphic route has the potential to become one of the most influential and long-lasting paradigms in the field of unconventional computing. Memristive and the recently proposed memfractive systems have been shown to display basic features of neural systems such as synaptic-like plasticity and memory features, so that they may offer a diverse playground to implement synaptic connections. In this review, we address various material-based strategies of implementing unconventional computing hardware: (i) electrochemical oscillators based on liquid metals and (ii) mem-devices exploiting Schottky barrier modulation in polycrystalline and disordered structures made of oxide or perovskite-type semiconductors. Both items (i) and (ii) build the two pillars of neuromimetic computing devices, which we will denote as synthetic neural networks. We expect that the current review will be of great interest for scientists aiming at bridging unconventional computing strategies with specific materials-based platforms. © 2020 The Japan Society of Applied Physics.

      @ARTICLE{Wlaźlak2020,
      author={Wlaźlak, E. and Przyczyna, D. and Gutierrez, R. and Cuniberti, G. and Szaciłowski, K.},
      title={Towards synthetic neural networks: Can artificial electrochemical neurons be coupled with artificial memristive synapses?},
      journal={Japanese Journal of Applied Physics},
      year={2020},
      volume={59},
      number={SI},
      doi={10.35848/1347-4065/ab7e11},
      art_number={SI0801},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85083111248&doi=10.35848%2f1347-4065%2fab7e11&partnerID=40&md5=031907c94341c99259665f25513267b4},
      affiliation={Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, al. Mickiewicza 30, Kraków, 30-059, Poland; Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, Kraków, 30-059, Poland; Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden University of Technology, Dresden, D-01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, D-01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, D-01062, Germany},
      abstract={The enormous amount of data generated nowadays worldwide is increasingly triggering the search for unconventional and more efficient ways of processing and classifying information, eventually able to transcend the conventional von Neumann-Turing computational central dogma. It is, therefore, greatly appealing to draw inspiration from less conventional but computationally more powerful systems such as the neural architecture of the human brain. This neuromorphic route has the potential to become one of the most influential and long-lasting paradigms in the field of unconventional computing. Memristive and the recently proposed memfractive systems have been shown to display basic features of neural systems such as synaptic-like plasticity and memory features, so that they may offer a diverse playground to implement synaptic connections. In this review, we address various material-based strategies of implementing unconventional computing hardware: (i) electrochemical oscillators based on liquid metals and (ii) mem-devices exploiting Schottky barrier modulation in polycrystalline and disordered structures made of oxide or perovskite-type semiconductors. Both items (i) and (ii) build the two pillars of neuromimetic computing devices, which we will denote as synthetic neural networks. We expect that the current review will be of great interest for scientists aiming at bridging unconventional computing strategies with specific materials-based platforms. © 2020 The Japan Society of Applied Physics.},
      document_type={Article},
      source={Scopus},
      }

  • Self-Assembly of Nanovoids in Si Microcrystals Epitaxially Grown on Deeply Patterned Substrates
    • A. Barzaghi, S. Firoozabadi, M. Salvalaglio, R. Bergamaschini, A. Ballabio, A. Beyer, M. Albani, J. Valente, A. Voigt, D. J. Paul, L. Miglio, F. Montalenti, K. Volz, G. Isella
    • Crystal Growth and Design 20, 2914-2920 (2020)
    • DOI   Abstract  

      We present an experimental and theoretical analysis of the formation of nanovoids within Si microcrystals epitaxially grown on Si patterned substrates. The growth conditions leading to the nucleation of nanovoids have been highlighted, and the roles played by the deposition rate, substrate temperature, and substrate pattern geometry are identified. By combining various scanning and transmission electron microscopy techniques, it has been possible to link the appearance pits of a few hundred nanometer width at the microcrystal surface with the formation of nanovoids within the crystal volume. A phase-field model, including surface diffusion and the flux of incoming material with shadowing effects, reproduces the qualitative features of the nanovoid formation thereby opening new perspectives for the bottom-up fabrication of 3D semiconductors microstructures. © 2020 American Chemical Society.

      @ARTICLE{Barzaghi20202914,
      author={Barzaghi, A. and Firoozabadi, S. and Salvalaglio, M. and Bergamaschini, R. and Ballabio, A. and Beyer, A. and Albani, M. and Valente, J. and Voigt, A. and Paul, D.J. and Miglio, L. and Montalenti, F. and Volz, K. and Isella, G.},
      title={Self-Assembly of Nanovoids in Si Microcrystals Epitaxially Grown on Deeply Patterned Substrates},
      journal={Crystal Growth and Design},
      year={2020},
      volume={20},
      number={5},
      pages={2914-2920},
      doi={10.1021/acs.cgd.9b01312},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084742273&doi=10.1021%2facs.cgd.9b01312&partnerID=40&md5=0b09c2a902831704aa762a57adcbd09d},
      affiliation={L-NESS, Dipartimento di Fisica, Politecnico di Milano, Via Anzani 42, Como, 22100, Italy; Materials Science Center, Faculty of Physics, Philipps-Universität Marburg, Hans-Meerweinstraße 6, Marburg, 35032, Germany; Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; L-NESS and Dipartimento di Scienza Dei Materiali, Università di Milano-Bicocca, Via R. Cozzi 55, Milano, I-20125, Italy; James Watt School of Engineering, University of Glasgow, Rankine Building, Oakfield Avenue, Glasgow, G12 8LT, United Kingdom},
      abstract={We present an experimental and theoretical analysis of the formation of nanovoids within Si microcrystals epitaxially grown on Si patterned substrates. The growth conditions leading to the nucleation of nanovoids have been highlighted, and the roles played by the deposition rate, substrate temperature, and substrate pattern geometry are identified. By combining various scanning and transmission electron microscopy techniques, it has been possible to link the appearance pits of a few hundred nanometer width at the microcrystal surface with the formation of nanovoids within the crystal volume. A phase-field model, including surface diffusion and the flux of incoming material with shadowing effects, reproduces the qualitative features of the nanovoid formation thereby opening new perspectives for the bottom-up fabrication of 3D semiconductors microstructures. © 2020 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • A Phase Field Approach to Trabecular Bone Remodeling
    • S. Aland, F. Stenger, R. Müller, A. Deutsch, A. Voigt
    • Frontiers in Applied Mathematics and Statistics 6, 12 (2020)
    • DOI   Abstract  

      We introduce a continuous modeling approach which combines elastic response of the trabecular bone structure with the concentration of signaling molecules within the bone and a mechanism for concentration dependent local bone formation and resorption. In an abstract setting bone can be considered as a shape changing structure. For similar problems in materials science phase field approximations have been established as an efficient computational tool. We adapt such an approach for trabecular bone remodeling. It allows for a smooth representation of the trabecular bone structure and drastically reduces computational costs if compared with traditional micro finite element approaches. We demonstrate the advantage of the approach within a minimal model. We quantitatively compare the results with established micro finite element approaches on simple geometries and consider the bone morphology within a bone segment obtained from μCT data of a sheep vertebra with realistic parameters. © Copyright © 2020 Aland, Stenger, Müller, Deutsch and Voigt.

      @ARTICLE{Aland2020,
      author={Aland, S. and Stenger, F. and Müller, R. and Deutsch, A. and Voigt, A.},
      title={A Phase Field Approach to Trabecular Bone Remodeling},
      journal={Frontiers in Applied Mathematics and Statistics},
      year={2020},
      volume={6},
      doi={10.3389/fams.2020.00012},
      art_number={12},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085109851&doi=10.3389%2ffams.2020.00012&partnerID=40&md5=95c55f5ab52fb9e4217709eda51fd2a7},
      affiliation={Faculty of Informatics/Mathematics, HTW Dresden, Dresden, Germany; Institut für Wissenschaftliches Rechnen, TU Dresden, Dresden, Germany; Center for Information Services and High Performance Computing, TU Dresden, Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, Germany; Center for Systems Biology Dresden (CSBD), Dresden, Germany},
      abstract={We introduce a continuous modeling approach which combines elastic response of the trabecular bone structure with the concentration of signaling molecules within the bone and a mechanism for concentration dependent local bone formation and resorption. In an abstract setting bone can be considered as a shape changing structure. For similar problems in materials science phase field approximations have been established as an efficient computational tool. We adapt such an approach for trabecular bone remodeling. It allows for a smooth representation of the trabecular bone structure and drastically reduces computational costs if compared with traditional micro finite element approaches. We demonstrate the advantage of the approach within a minimal model. We quantitatively compare the results with established micro finite element approaches on simple geometries and consider the bone morphology within a bone segment obtained from μCT data of a sheep vertebra with realistic parameters. © Copyright © 2020 Aland, Stenger, Müller, Deutsch and Voigt.},
      author_keywords={bone remodeling; mechanosensing; phase-field; topology optimization; trabecular bone},
      document_type={Article},
      source={Scopus},
      }

  • Properties of surface Landau-de GennesQ-tensor models
    • M. Nestler, I. Nitschke, H. Löwen, A. Voigt
    • Soft Matter 16, 4032-4042 (2020)
    • DOI   Abstract  

      Uniaxial nematic liquid crystals whose molecular orientation is subjected to tangential anchoring on a curved surface offer a non trivial interplay between the geometry and the topology of the surface and the orientational degree of freedom. We consider a general thin film limit of a Landau-de GennesQ-tensor model which retains the characteristics of the 3D model. From this, previously proposed surface models follow as special cases. We compare fundamental properties, such as the alignment of the orientational degrees of freedom with principle curvature lines, order parameter symmetry and phase transition type for these models, and suggest experiments to identify suitable model assumptions. © The Royal Society of Chemistry 2020.

      @ARTICLE{Nestler20204032,
      author={Nestler, M. and Nitschke, I. and Löwen, H. and Voigt, A.},
      title={Properties of surface Landau-de GennesQ-tensor models},
      journal={Soft Matter},
      year={2020},
      volume={16},
      number={16},
      pages={4032-4042},
      doi={10.1039/c9sm02475a},
      note={cited By 2},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084175201&doi=10.1039%2fc9sm02475a&partnerID=40&md5=0a389dc8161a9edb5f419b5a7b017256},
      affiliation={Institut für Wissenschaftliches Rechnen, Technische Universität Dresden, Dresden, 01062, Germany; Institut für Theoretische Physik II - Soft Matter, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, 40225, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Center for Systems Biology Dresden (CSBD), Pfotenhauerstr. 108, Dresden, 01307, Germany},
      abstract={Uniaxial nematic liquid crystals whose molecular orientation is subjected to tangential anchoring on a curved surface offer a non trivial interplay between the geometry and the topology of the surface and the orientational degree of freedom. We consider a general thin film limit of a Landau-de GennesQ-tensor model which retains the characteristics of the 3D model. From this, previously proposed surface models follow as special cases. We compare fundamental properties, such as the alignment of the orientational degrees of freedom with principle curvature lines, order parameter symmetry and phase transition type for these models, and suggest experiments to identify suitable model assumptions. © The Royal Society of Chemistry 2020.},
      document_type={Article},
      source={Scopus},
      }

  • Bending rigidities and universality of flexural modes in 2D crystals
    • A. Croy
    • JPhys Materials 3, 02LT03 (2020)
    • DOI   Abstract  

      The existence of flexural modes with a quadratic phonon-dispersion is a distinguishing property of two-dimensional materials and has important consequences for their properties. Here, we deduce theoretically within the harmonic approximation the conditions for which orthotropic two-dimensional materials display a flexural mode. Further, we derive formulae for the calculation of the corresponding bending rigidities using the equilibrium structure and the second-order force constants as input. This completes the description of the elasticity of 2D crystals. Our findings are exemplarily validated by ab initio calculations of the phonon dispersions of four representative materials. © 2020 The Author(s). Published by IOP Publishing Ltd.

      @ARTICLE{Croy2020,
      author={Croy, A.},
      title={Bending rigidities and universality of flexural modes in 2D crystals},
      journal={JPhys Materials},
      year={2020},
      volume={3},
      number={2},
      doi={10.1088/2515-7639/ab8271},
      art_number={02LT03},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85099776349&doi=10.1088%2f2515-7639%2fab8271&partnerID=40&md5=7b8fdca9be65c6c205684eea27015b9c},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01069, Germany},
      abstract={The existence of flexural modes with a quadratic phonon-dispersion is a distinguishing property of two-dimensional materials and has important consequences for their properties. Here, we deduce theoretically within the harmonic approximation the conditions for which orthotropic two-dimensional materials display a flexural mode. Further, we derive formulae for the calculation of the corresponding bending rigidities using the equilibrium structure and the second-order force constants as input. This completes the description of the elasticity of 2D crystals. Our findings are exemplarily validated by ab initio calculations of the phonon dispersions of four representative materials. © 2020 The Author(s). Published by IOP Publishing Ltd.},
      author_keywords={2D Mmterials; Bending rigidity; Phonon dispersion; Strain engineering},
      document_type={Article},
      source={Scopus},
      }

  • A coarse-grained phase-field crystal model of plastic motion
    • M. Salvalaglio, L. Angheluta, Z. -F. Huang, A. Voigt, K. R. Elder, J. Viñals
    • Journal of the Mechanics and Physics of Solids 137, 103856 (2020)
    • DOI   Abstract  

      The phase-field crystal model in an amplitude equation approximation is shown to provide an accurate description of the deformation field in defected crystalline structures, as well as of dislocation motion. We analyze in detail stress regularization at a dislocation core given by the model, and show how the Burgers vector density can be directly computed from the topological singularities of the phase-field amplitudes. Distortions arising from these amplitudes are then supplemented with non-singular displacements to enforce mechanical equilibrium. This allows for a consistent separation of plastic and elastic time scales in this framework. A finite element method is introduced to solve the combined amplitude and elasticity equations, which is applied to a few prototypical configurations in two spatial dimensions for a crystal of triangular lattice symmetry: i) the stress field induced by an edge dislocation with an analysis of how the amplitude equation regularizes stresses near the dislocation core, ii) the motion of a dislocation dipole as a result of its internal interaction, and iii) the shrinkage of a rotated grain. We compare our results with those given by other extensions of classical elasticity theory, such as strain-gradient elasticity and methods based on the smoothing of Burgers vector densities near defect cores. © 2019

      @ARTICLE{Salvalaglio2020,
      author={Salvalaglio, M. and Angheluta, L. and Huang, Z.-F. and Voigt, A. and Elder, K.R. and Viñals, J.},
      title={A coarse-grained phase-field crystal model of plastic motion},
      journal={Journal of the Mechanics and Physics of Solids},
      year={2020},
      volume={137},
      doi={10.1016/j.jmps.2019.103856},
      art_number={103856},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077304464&doi=10.1016%2fj.jmps.2019.103856&partnerID=40&md5=ab2a8ab2bb9b8945ab51e0f0df83aad5},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Hong Kong Institute for Advanced Studies and Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong SAR, China; PoreLab, The Njord Centre, Department of Physics, University of Oslo, P. O. Box 1048, Oslo, 0316, Norway; Department of Physics and Astronomy, Wayne State University, Detroit, MI 48201, United States; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Department of Physics, Oakland University, Rochester, MI 48309, United States; School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455, United States},
      abstract={The phase-field crystal model in an amplitude equation approximation is shown to provide an accurate description of the deformation field in defected crystalline structures, as well as of dislocation motion. We analyze in detail stress regularization at a dislocation core given by the model, and show how the Burgers vector density can be directly computed from the topological singularities of the phase-field amplitudes. Distortions arising from these amplitudes are then supplemented with non-singular displacements to enforce mechanical equilibrium. This allows for a consistent separation of plastic and elastic time scales in this framework. A finite element method is introduced to solve the combined amplitude and elasticity equations, which is applied to a few prototypical configurations in two spatial dimensions for a crystal of triangular lattice symmetry: i) the stress field induced by an edge dislocation with an analysis of how the amplitude equation regularizes stresses near the dislocation core, ii) the motion of a dislocation dipole as a result of its internal interaction, and iii) the shrinkage of a rotated grain. We compare our results with those given by other extensions of classical elasticity theory, such as strain-gradient elasticity and methods based on the smoothing of Burgers vector densities near defect cores. © 2019},
      author_keywords={coarse-graining; crystal plasticity; dislocation motion; finite element method; phase-field crystal},
      document_type={Article},
      source={Scopus},
      }

  • Magnetically induced/enhanced coarsening in thin films
    • R. Backofen, A. Voigt
    • Physical Review Materials 4, 023404 (2020)
    • DOI   Abstract  

      External magnetic fields influence the microstructure of polycrystalline materials. We explore the influence of strong external magnetic fields on the long time scaling of grain size during coarsening in thin films with an extended phase-field-crystal model. Additionally, the change of various geometrical and topological properties is studied. In a situation which leads to stagnation, an applied external magnetic field can induce further grain growth. The induced driving force due to the magnetic anisotropy defines the magnetic influence of the external magnetic field. Different scaling regimes are identified dependent on the magnetization. At the beginning, the scaling exponent increases with the strength of the magnetization. Later, when the texture becomes dominated by grains preferably aligned with the external magnetic field, the scaling exponent becomes independent of the strength of the magnetization or stagnation occurs. We discuss how the magnetic influence change the effect of retarding or pinning forces, which are known to influence the scaling exponent. We further study the influence of the magnetic field on the grain size distribution (GSD), next-neighbor distribution (NND) as well as grain shape and orientation. If possible, we compare our predictions with experimental findings. © 2020 American Physical Society.

      @ARTICLE{Backofen2020,
      author={Backofen, R. and Voigt, A.},
      title={Magnetically induced/enhanced coarsening in thin films},
      journal={Physical Review Materials},
      year={2020},
      volume={4},
      number={2},
      doi={10.1103/PhysRevMaterials.4.023404},
      art_number={023404},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082656985&doi=10.1103%2fPhysRevMaterials.4.023404&partnerID=40&md5=b36f1f6e1ae918421394ca249d6706d3},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany},
      abstract={External magnetic fields influence the microstructure of polycrystalline materials. We explore the influence of strong external magnetic fields on the long time scaling of grain size during coarsening in thin films with an extended phase-field-crystal model. Additionally, the change of various geometrical and topological properties is studied. In a situation which leads to stagnation, an applied external magnetic field can induce further grain growth. The induced driving force due to the magnetic anisotropy defines the magnetic influence of the external magnetic field. Different scaling regimes are identified dependent on the magnetization. At the beginning, the scaling exponent increases with the strength of the magnetization. Later, when the texture becomes dominated by grains preferably aligned with the external magnetic field, the scaling exponent becomes independent of the strength of the magnetization or stagnation occurs. We discuss how the magnetic influence change the effect of retarding or pinning forces, which are known to influence the scaling exponent. We further study the influence of the magnetic field on the grain size distribution (GSD), next-neighbor distribution (NND) as well as grain shape and orientation. If possible, we compare our predictions with experimental findings. © 2020 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • ProMAD: Semiquantitative densitometric measurement of protein microarrays
    • A. Jaeschke, H. Eckert, L. J. Bray
    • BMC Bioinformatics 21, 72 (2020)
    • DOI   Abstract  

      Background: Protein microarrays are a versatile and widely used tool for analyzing complex protein mixtures. Membrane arrays utilize antibodies which are captured on a membrane to specifically immobilize several proteins of interest at once. Using detection antibodies, the bound protein-Antibody-complex is converted into visual signals, which can be quantified using densitometry. The reliability of such densitometric assessments depends on a variety of factors, not only sample preparation and the choice of acquisition device but also the selected analysis software and the algorithms used for readout and processing data. Currently available software packages use a single image of a membrane at an optimal exposure time selected for that specific experimental framework. This selection is based on a user’s best guess and is subject to inter-user variability or the acquisition device algorithm. With modern image acquisition systems proving the capacity to collect signal development over time, this information can be used to improve densitometric measurements. Here we introduce proMAD, a toolkit for protein microarray analysis providing a novel systemic approach for the quantification of membrane arrays based on the kinetics of the analytical reaction. Results: Briefly, our toolkit ensures an exact membrane alignment, utilizing basic computer vision techniques. It also provides a stable method to estimate the background light level. Finally, we model the light production over time, utilizing the knowledge about the reaction kinetics of the underlying horseradish peroxidase-based signal detection method. Conclusion: proMAD incorporates the reaction kinetics of the enzyme to model the signal development over time for each membrane creating an individual, self-referencing concept. Variations of membranes within a given experimental set up can be accounted for, allowing for a better comparison of such. While the open-source library can be implemented in existing workflows and used for highly user-Tailored analytic setups, the web application, on the other hand, provides easy platform-independent access to the core algorithm to a wide range of researchers. proMAD’s inherent flexibility has the potential to cover a wide range of use-cases and enables the automation of data analytic tasks. © 2020 The Author(s).

      @ARTICLE{Jaeschke2020,
      author={Jaeschke, A. and Eckert, H. and Bray, L.J.},
      title={ProMAD: Semiquantitative densitometric measurement of protein microarrays},
      journal={BMC Bioinformatics},
      year={2020},
      volume={21},
      number={1},
      doi={10.1186/s12859-020-3402-4},
      art_number={72},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85080938471&doi=10.1186%2fs12859-020-3402-4&partnerID=40&md5=b269ead70a101f1aab0af692f5e975aa},
      affiliation={Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, QLD 4059, Australia; School of Mechanical, Medical and Process Engineering, Science and Engineering Faculty, Queensland University of Technology, Kelvin Grove, QLD 4059, Australia; Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, Germany},
      abstract={Background: Protein microarrays are a versatile and widely used tool for analyzing complex protein mixtures. Membrane arrays utilize antibodies which are captured on a membrane to specifically immobilize several proteins of interest at once. Using detection antibodies, the bound protein-Antibody-complex is converted into visual signals, which can be quantified using densitometry. The reliability of such densitometric assessments depends on a variety of factors, not only sample preparation and the choice of acquisition device but also the selected analysis software and the algorithms used for readout and processing data. Currently available software packages use a single image of a membrane at an optimal exposure time selected for that specific experimental framework. This selection is based on a user's best guess and is subject to inter-user variability or the acquisition device algorithm. With modern image acquisition systems proving the capacity to collect signal development over time, this information can be used to improve densitometric measurements. Here we introduce proMAD, a toolkit for protein microarray analysis providing a novel systemic approach for the quantification of membrane arrays based on the kinetics of the analytical reaction. Results: Briefly, our toolkit ensures an exact membrane alignment, utilizing basic computer vision techniques. It also provides a stable method to estimate the background light level. Finally, we model the light production over time, utilizing the knowledge about the reaction kinetics of the underlying horseradish peroxidase-based signal detection method. Conclusion: proMAD incorporates the reaction kinetics of the enzyme to model the signal development over time for each membrane creating an individual, self-referencing concept. Variations of membranes within a given experimental set up can be accounted for, allowing for a better comparison of such. While the open-source library can be implemented in existing workflows and used for highly user-Tailored analytic setups, the web application, on the other hand, provides easy platform-independent access to the core algorithm to a wide range of researchers. proMAD's inherent flexibility has the potential to cover a wide range of use-cases and enables the automation of data analytic tasks. © 2020 The Author(s).},
      author_keywords={Densitometry; Membrane antibody array; Protein microarray; Python; Web application},
      document_type={Article},
      source={Scopus},
      }

  • An efficient phase-field model for fatigue fracture in ductile materials
    • M. Seiler, T. Linse, P. Hantschke, M. Kästner
    • Engineering Fracture Mechanics 224, 106807 (2020)
    • DOI   Abstract  

      Fatigue fracture in ductile materials, e.g. metals, is caused by cyclic plasticity. Especially regarding the high numbers of load cycles, plastic material models resolving the full loading path are computationally very demanding. Herein, a model with particularly small computational effort is presented. It provides a macroscopic, phenomenological description of fatigue fracture by combining the phase-field method for brittle fracture with a classic durability concept. A local lifetime variable is obtained, which degrades the fracture resistance progressively. By deriving the stress-strain path from cyclic material characteristics, only one increment per load cycle is needed at maximum. The model allows to describe fatigue crack initiation, propagation and residual fracture and can reproduce Paris behaviour. © 2019 Elsevier Ltd

      @ARTICLE{Seiler2020,
      author={Seiler, M. and Linse, T. and Hantschke, P. and Kästner, M.},
      title={An efficient phase-field model for fatigue fracture in ductile materials},
      journal={Engineering Fracture Mechanics},
      year={2020},
      volume={224},
      doi={10.1016/j.engfracmech.2019.106807},
      art_number={106807},
      note={cited By 11},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076558659&doi=10.1016%2fj.engfracmech.2019.106807&partnerID=40&md5=f0ce2ee119e880df456c5fa7eccf527b},
      affiliation={Chair of Computational and Experimental Solid Mechanics, TU Dresden, Dresden, Germany; Structural Durability Group, TU Dresden, Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, Germany},
      abstract={Fatigue fracture in ductile materials, e.g. metals, is caused by cyclic plasticity. Especially regarding the high numbers of load cycles, plastic material models resolving the full loading path are computationally very demanding. Herein, a model with particularly small computational effort is presented. It provides a macroscopic, phenomenological description of fatigue fracture by combining the phase-field method for brittle fracture with a classic durability concept. A local lifetime variable is obtained, which degrades the fracture resistance progressively. By deriving the stress-strain path from cyclic material characteristics, only one increment per load cycle is needed at maximum. The model allows to describe fatigue crack initiation, propagation and residual fracture and can reproduce Paris behaviour. © 2019 Elsevier Ltd},
      author_keywords={Ductile; Fatigue; Local strain approach; Paris law; Phase-field},
      document_type={Article},
      source={Scopus},
      }

  • Nanosensors-Assisted quantitative analysis of biochemical processes in droplets
    • D. Belyaev, J. Schütt, B. Ibarlucea, T. Rim, L. Baraban, G. Cuniberti
    • Micromachines 11, 138 (2020)
    • DOI   Abstract  

      Here, we present a miniaturized lab-on-a-chip detecting system for an all-electric and label-free analysis of the emulsion droplets incorporating the nanoscopic silicon nanowires-based field-effect transistors (FETs). We specifically focus on the analysis of β-galactosidase e.g., activity, which is an important enzyme of the glycolysis metabolic pathway. Furthermore, the efficiency of the synthesis and action of β-galactosidase can be one of the markers for several diseases, e.g., cancer, hyper/hypoglycemia, cell senescence, or other disruptions in cell functioning. We measure the reaction and reaction kinetics-associated shift of the source-to-drain current Isd in the system, which is caused by the change of the ionic strength of the microenvironment. With these results, we demonstrate that the ion-sensitive FETs are able to sense the interior of the aqueous reactors; thus, the conjunction of miniature nanosensors and droplet-based microfluidic systems conceptually opens a new route toward a sensitive, optics-less analysis of biochemical processes. © 2020 by the authors.

      @ARTICLE{Belyaev2020,
      author={Belyaev, D. and Schütt, J. and Ibarlucea, B. and Rim, T. and Baraban, L. and Cuniberti, G.},
      title={Nanosensors-Assisted quantitative analysis of biochemical processes in droplets},
      journal={Micromachines},
      year={2020},
      volume={11},
      number={2},
      doi={10.3390/mi11020138},
      art_number={138},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081283806&doi=10.3390%2fmi11020138&partnerID=40&md5=e1150f9256f6ee93f4b910054e17906b},
      affiliation={Max Bergmann Center of Biomaterials and Institute for Materials Science, Technische Universität Dresden, Dresden, 01069, Germany; Technische Universität Dresden, Center for Advancing Electronics Dresden, Dresden, 01062, Germany; Department of Creative IT Engineering, Pohang University of Science and Technology, Pohang, 37673, South Korea; Dresden Center for Computational Materials Science, Dresden, 01062, Germany},
      abstract={Here, we present a miniaturized lab-on-a-chip detecting system for an all-electric and label-free analysis of the emulsion droplets incorporating the nanoscopic silicon nanowires-based field-effect transistors (FETs). We specifically focus on the analysis of β-galactosidase e.g., activity, which is an important enzyme of the glycolysis metabolic pathway. Furthermore, the efficiency of the synthesis and action of β-galactosidase can be one of the markers for several diseases, e.g., cancer, hyper/hypoglycemia, cell senescence, or other disruptions in cell functioning. We measure the reaction and reaction kinetics-associated shift of the source-to-drain current Isd in the system, which is caused by the change of the ionic strength of the microenvironment. With these results, we demonstrate that the ion-sensitive FETs are able to sense the interior of the aqueous reactors; thus, the conjunction of miniature nanosensors and droplet-based microfluidic systems conceptually opens a new route toward a sensitive, optics-less analysis of biochemical processes. © 2020 by the authors.},
      author_keywords={Droplet-based microfluidics; Enzymatic reaction; Lab-on-a-chip; Nanosensor; Point-of-care diagnostics; Silicon nanowire-based field-effect transistor; ß-galactosidase assay},
      document_type={Article},
      source={Scopus},
      }

  • Mechanical Transmission of Rotational Motion between Molecular-Scale Gears
    • H. -H. Lin, A. Croy, R. Gutierrez, C. Joachim, G. Cuniberti
    • Physical Review Applied 13, 034024 (2020)
    • DOI   Abstract  

      The manipulation and coupling of molecule gears is the first step toward realizing molecular-scale mechanical machines. Here, we theoretically investigate the behavior of such gears using molecular-dynamics simulations. Within a nearly rigid-body approximation, we reduce the dynamics of the gears to the rotational motion around the orientation vector. This allows us to study their behavior based on a few collective variables. Specifically, for a single hexa(4-tert-butylphenyl)benzene molecule, we show that the rotational-angle dynamics correspond to those of a Brownian rotor. For two such coupled gears, we extract the effective interaction potential and find that it is strongly dependent on the center-of-mass distance. Finally, we study the collective motion of a train of gears. We demonstrate the existence of three different regimes, depending on the magnitude of the driving torque of the first gear: Underdriving, driving, and overdriving, which correspond, respectively, to no collective rotation, collective rotation, and only single-gear rotation. This behavior can be understood in terms of a simplified interaction potential. © 2020 American Physical Society.

      @ARTICLE{Lin2020,
      author={Lin, H.-H. and Croy, A. and Gutierrez, R. and Joachim, C. and Cuniberti, G.},
      title={Mechanical Transmission of Rotational Motion between Molecular-Scale Gears},
      journal={Physical Review Applied},
      year={2020},
      volume={13},
      number={3},
      doi={10.1103/PhysRevApplied.13.034024},
      art_number={034024},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082880360&doi=10.1103%2fPhysRevApplied.13.034024&partnerID=40&md5=ec1c9ba5f0f4d073855055e44f15151e},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, Tu Dresden, Dresden, 01069, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany; Gns and Mana Satellite, CEMES-CNRS, 29 rue J. Marvig, Toulouse Cedex, 31055, France; Dresden Center for Computational Materials Science, Tu Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, Tu Dresden, 01062 Dresden, Germany, Germany},
      abstract={The manipulation and coupling of molecule gears is the first step toward realizing molecular-scale mechanical machines. Here, we theoretically investigate the behavior of such gears using molecular-dynamics simulations. Within a nearly rigid-body approximation, we reduce the dynamics of the gears to the rotational motion around the orientation vector. This allows us to study their behavior based on a few collective variables. Specifically, for a single hexa(4-tert-butylphenyl)benzene molecule, we show that the rotational-angle dynamics correspond to those of a Brownian rotor. For two such coupled gears, we extract the effective interaction potential and find that it is strongly dependent on the center-of-mass distance. Finally, we study the collective motion of a train of gears. We demonstrate the existence of three different regimes, depending on the magnitude of the driving torque of the first gear: Underdriving, driving, and overdriving, which correspond, respectively, to no collective rotation, collective rotation, and only single-gear rotation. This behavior can be understood in terms of a simplified interaction potential. © 2020 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Dirac fermions and flat bands in the ideal kagome metal FeSn
    • M. Kang, L. Ye, S. Fang, J. -S. You, A. Levitan, M. Han, J. I. Facio, C. Jozwiak, A. Bostwick, E. Rotenberg, M. K. Chan, R. D. McDonald, D. Graf, K. Kaznatcheev, E. Vescovo, D. C. Bell, E. Kaxiras, J. van den Brink, M. Richter, M. Prasad Ghimire, J. G. Checkelsky, R. Comin
    • Nature Materials 19, 163-169 (2020)
    • DOI   Abstract  

      A kagome lattice of 3d transition metal ions is a versatile platform for correlated topological phases hosting symmetry-protected electronic excitations and magnetic ground states. However, the paradigmatic states of the idealized two-dimensional kagome lattice—Dirac fermions and flat bands—have not been simultaneously observed. Here, we use angle-resolved photoemission spectroscopy and de Haas–van Alphen quantum oscillations to reveal coexisting surface and bulk Dirac fermions as well as flat bands in the antiferromagnetic kagome metal FeSn, which has spatially decoupled kagome planes. Our band structure calculations and matrix element simulations demonstrate that the bulk Dirac bands arise from in-plane localized Fe-3d orbitals, and evidence that the coexisting Dirac surface state realizes a rare example of fully spin-polarized two-dimensional Dirac fermions due to spin-layer locking in FeSn. The prospect to harness these prototypical excitations in a kagome lattice is a frontier of great promise at the confluence of topology, magnetism and strongly correlated physics. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.

      @ARTICLE{Kang2020163,
      author={Kang, M. and Ye, L. and Fang, S. and You, J.-S. and Levitan, A. and Han, M. and Facio, J.I. and Jozwiak, C. and Bostwick, A. and Rotenberg, E. and Chan, M.K. and McDonald, R.D. and Graf, D. and Kaznatcheev, K. and Vescovo, E. and Bell, D.C. and Kaxiras, E. and van den Brink, J. and Richter, M. and Prasad Ghimire, M. and Checkelsky, J.G. and Comin, R.},
      title={Dirac fermions and flat bands in the ideal kagome metal FeSn},
      journal={Nature Materials},
      year={2020},
      volume={19},
      number={2},
      pages={163-169},
      doi={10.1038/s41563-019-0531-0},
      note={cited By 43},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076512559&doi=10.1038%2fs41563-019-0531-0&partnerID=40&md5=ec66db33a2ea68a44b84f7d39091e452},
      affiliation={Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, United States; Department of Physics, Harvard University, Cambridge, MA, United States; Leibniz Institute for Solid State and Materials Research, IFW Dresden, Dresden, Germany; Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, CA, United States; National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, NM, United States; National High Magnetic Field Laboratory, Tallahassee, FL, United States; National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, United States; John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, United States; Center for Nanoscale systems, Harvard University, Cambridge, MA, United States; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, Germany; Central Department of Physics, Tribhuvan University, Kirtipur, Kathmandu, Nepal},
      abstract={A kagome lattice of 3d transition metal ions is a versatile platform for correlated topological phases hosting symmetry-protected electronic excitations and magnetic ground states. However, the paradigmatic states of the idealized two-dimensional kagome lattice—Dirac fermions and flat bands—have not been simultaneously observed. Here, we use angle-resolved photoemission spectroscopy and de Haas–van Alphen quantum oscillations to reveal coexisting surface and bulk Dirac fermions as well as flat bands in the antiferromagnetic kagome metal FeSn, which has spatially decoupled kagome planes. Our band structure calculations and matrix element simulations demonstrate that the bulk Dirac bands arise from in-plane localized Fe-3d orbitals, and evidence that the coexisting Dirac surface state realizes a rare example of fully spin-polarized two-dimensional Dirac fermions due to spin-layer locking in FeSn. The prospect to harness these prototypical excitations in a kagome lattice is a frontier of great promise at the confluence of topology, magnetism and strongly correlated physics. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.},
      document_type={Article},
      source={Scopus},
      }

  • Enhanced photocatalytic activity of au/TiO2 nanoparticles against ciprofloxacin
    • P. Martins, S. Kappert, H. N. Le, V. Sebastian, K. Kühn, M. Alves, L. Pereira, G. Cuniberti, M. Melle-Franco, S. Lanceros-Méndez
    • Catalysts 10, 234 (2020)
    • DOI   Abstract  

      In the last decades, photocatalysis has arisen as a solution to degrade emerging pollutants such as antibiotics. However, the reduced photoactivation of TiO2 under visible radiation constitutes a major drawback because 95% of sunlight radiation is not being used in this process. Thus, it is critical to modify TiO2 nanoparticles to improve the ability to absorb visible radiation from sunlight. This work reports on the synthesis of TiO2 nanoparticles decorated with gold (Au) nanoparticles by deposition-precipitation method for enhanced photocatalytic activity. The produced nanocomposites absorb 40% to 55% more radiation in the visible range than pristine TiO2, the best results being obtained for the synthesis performed at 25◦C and with Au loading of 0.05 to 0.1 wt. %. Experimental tests yielded a higher photocatalytic degradation of 91% and 49% of ciprofloxacin (5 mg/L) under UV and visible radiation, correspondingly. Computational modeling supports the experimental results, showing the ability of Au to bind TiO2 anatase surfaces, the relevant role of Au transferring electrons, and the high affinity of ciprofloxacin to both Au and TiO2 surfaces. Hence, the present work represents a reliable approach to produce efficient photocatalytic materials and an overall contribution in the development of high-performance Au/TiO2 photocatalytic nanostructures through the optimization of the synthesis parameters, photocatalytic conditions, and computational modeling. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

      @ARTICLE{Martins2020,
      author={Martins, P. and Kappert, S. and Le, H.N. and Sebastian, V. and Kühn, K. and Alves, M. and Pereira, L. and Cuniberti, G. and Melle-Franco, M. and Lanceros-Méndez, S.},
      title={Enhanced photocatalytic activity of au/TiO2 nanoparticles against ciprofloxacin},
      journal={Catalysts},
      year={2020},
      volume={10},
      number={2},
      doi={10.3390/catal10020234},
      art_number={234},
      note={cited By 4},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079661606&doi=10.3390%2fcatal10020234&partnerID=40&md5=8149b222aa2ccd735e37d80e7175f797},
      affiliation={Department of Physics/Centre of Biological Engineering, University of Minho, Braga, 4710-057, Portugal; IB-S—Institute for Research and Innovation on Bio-Sustainability, University of Minho, Braga, 4710-057, Portugal; Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden Dresden, Dresden, 01062, Germany; Department of Chemical Engineering, Hanoi University of Science and Technology, Hanoi, 10000, Viet Nam; Department of Chemical Engineering, Aragon Institute of Nanoscience (INA), University of Zaragoza, Campus Río Ebro-Edificio I+D, C/Poeta Mariano Esquillor S/N, Zaragoza, 50018, Spain; Networking Research Centre on Bioengineering, Biomaterials and Nanomedicine, Centro de Investigacion Biomédica en Red—Bioengenharía, Biomateriales e Nanomedicina, Madrid, 28029, Spain; Dresden Center for Computational Materials Science, Technische Universität Dresden Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden Dresden, Dresden, 01062, Germany; Centro de Investigação em Materiais Cerâmicos e Compósitos, Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, Aveiro, 3810-193, Portugal; BCMaterials, Basque Center for Materials, Applications, and Nanostructures, Universidad del País Basco—Euskal Herriko Unibertsitatea, Science Park, Leioa, 48940, Spain; IKERBASQUE, Basque Foundation for Science, Bilbao, 48013, Spain},
      abstract={In the last decades, photocatalysis has arisen as a solution to degrade emerging pollutants such as antibiotics. However, the reduced photoactivation of TiO2 under visible radiation constitutes a major drawback because 95% of sunlight radiation is not being used in this process. Thus, it is critical to modify TiO2 nanoparticles to improve the ability to absorb visible radiation from sunlight. This work reports on the synthesis of TiO2 nanoparticles decorated with gold (Au) nanoparticles by deposition-precipitation method for enhanced photocatalytic activity. The produced nanocomposites absorb 40% to 55% more radiation in the visible range than pristine TiO2, the best results being obtained for the synthesis performed at 25◦C and with Au loading of 0.05 to 0.1 wt. %. Experimental tests yielded a higher photocatalytic degradation of 91% and 49% of ciprofloxacin (5 mg/L) under UV and visible radiation, correspondingly. Computational modeling supports the experimental results, showing the ability of Au to bind TiO2 anatase surfaces, the relevant role of Au transferring electrons, and the high affinity of ciprofloxacin to both Au and TiO2 surfaces. Hence, the present work represents a reliable approach to produce efficient photocatalytic materials and an overall contribution in the development of high-performance Au/TiO2 photocatalytic nanostructures through the optimization of the synthesis parameters, photocatalytic conditions, and computational modeling. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.},
      author_keywords={Antibiotics; Au-TiO2; Emergent contaminants; GFN-xTB; Nanocatalyst; Photocatalysis},
      document_type={Article},
      source={Scopus},
      }

  • Dodecacene Generated on Surface: Reopening of the Energy Gap
    • F. Eisenhut, T. Kühne, F. García, S. Fernández, E. Guitián, D. Pérez, G. Trinquier, G. Cuniberti, C. Joachim, D. Peña, F. Moresco
    • ACS Nano 14, 1011-1017 (2020)
    • DOI   Abstract  

      The acene series represents a model system to investigate the intriguing electronic properties of extended π-electron structures in the one-dimensional limit, which are important for applications in electronics and spintronics and for the fundamental understanding of electronic transport. Here, we present the on-surface generation of the longest acene obtained so far: dodecacene. Scanning tunneling spectroscopy gives access to the energy position and spatial distribution of its electronic states on the Au(111) surface. We observe that, after a progressive closing of the gap and a stabilization to about 1 eV at the length of decacene and undecacene, the energy gap of dodecacene unexpectedly increases to 1.4 eV. Considering the acene series as an exemplary general case, we discuss the evolution with length of the single tunneling resonances in comparison with ionization energy, electronic affinity, and optical gap. Copyright © 2019 American Chemical Society.

      @ARTICLE{Eisenhut20201011,
      author={Eisenhut, F. and Kühne, T. and García, F. and Fernández, S. and Guitián, E. and Pérez, D. and Trinquier, G. and Cuniberti, G. and Joachim, C. and Peña, D. and Moresco, F.},
      title={Dodecacene Generated on Surface: Reopening of the Energy Gap},
      journal={ACS Nano},
      year={2020},
      volume={14},
      number={1},
      pages={1011-1017},
      doi={10.1021/acsnano.9b08456},
      note={cited By 21},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077014331&doi=10.1021%2facsnano.9b08456&partnerID=40&md5=4db539b2ca3b61ab0a68e2a4df9a372d},
      affiliation={Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01069, Germany; Institute for Materials Science, TU Dresden, Dresden, 01069, Germany; Centro de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Departamento de Química Orgánica, Universidade de Santiago de Compostela, Santiago de Compostela, 15782, Spain; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01069, Germany; GNS and MANA Satellite, CEMES, CNRS, 29 rue J. Marvig, Cedex Toulouse, 31055, France; Laboratoire de Chimie et Physique Quantiques, IRSAMC-CNRS-UMR5626, Université Paul-Sabatier (Toulouse III), Cedex 4 Toulouse, 31062, France},
      abstract={The acene series represents a model system to investigate the intriguing electronic properties of extended π-electron structures in the one-dimensional limit, which are important for applications in electronics and spintronics and for the fundamental understanding of electronic transport. Here, we present the on-surface generation of the longest acene obtained so far: dodecacene. Scanning tunneling spectroscopy gives access to the energy position and spatial distribution of its electronic states on the Au(111) surface. We observe that, after a progressive closing of the gap and a stabilization to about 1 eV at the length of decacene and undecacene, the energy gap of dodecacene unexpectedly increases to 1.4 eV. Considering the acene series as an exemplary general case, we discuss the evolution with length of the single tunneling resonances in comparison with ionization energy, electronic affinity, and optical gap. Copyright © 2019 American Chemical Society.},
      author_keywords={dodecacene; electronic resonances; energy gap; on-surface synthesis; poly-radical character; scanning tunneling microscopy; scanning tunneling spectroscopy},
      document_type={Article},
      source={Scopus},
      }

  • GITT Analysis of Lithium Insertion Cathodes for Determining the Lithium Diffusion Coefficient at Low Temperature: Challenges and Pitfalls
    • A. Nickol, T. Schied, C. Heubner, M. Schneider, A. Michaelis, M. Bobeth, G. Cuniberti
    • Journal of the Electrochemical Society 167, 090546 (2020)
    • DOI   Abstract  

      Understanding the diffusion of lithium ions in electrode materials for lithium ion batteries is of great importance for their knowledge-based optimization and development of novel materials and cell designs. The galvanostatic intermittent titration technique (GITT) is widely applied in battery research to study the diffusion of lithium in anode and cathode materials depending on the degree of lithiation. While transport properties of electrode materials at high and ambient temperatures are largely available, low temperature diffusion and rate coefficients are hardly reported in the literature and vary by orders of magnitude for identical active materials. Herein, we demonstrate and discuss several challenges and pitfalls in the application and evaluation of GITT measurements for determining the effective chemical lithium ion diffusion coefficient in lithium insertion electrodes, which become especially important at low temperature. This includes theoretical considerations and an experimental analysis of the promising cathode material LiNi0.5Co0.2Mn0.3O2 (NCM523) in the wide temperature range of -40 °C to 40 °C. We show how the choice of experimental conditions for the GITT measurements and of the subsequent mathematical evaluation significantly influence the derived diffusion coefficient. The results suggest that the large scattering of reported values of the diffusion coefficient could be caused by the use of different evaluation procedures. Simple calculation methods appear to be less suited the lower the temperature is. It is shown that the complementary use of GITT and EIS supplemented by detailed knowledge of the microstructure of the electrode significantly improves the accuracy of determining the diffusion coefficient. © 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.

      @ARTICLE{Nickol2020,
      author={Nickol, A. and Schied, T. and Heubner, C. and Schneider, M. and Michaelis, A. and Bobeth, M. and Cuniberti, G.},
      title={GITT Analysis of Lithium Insertion Cathodes for Determining the Lithium Diffusion Coefficient at Low Temperature: Challenges and Pitfalls},
      journal={Journal of the Electrochemical Society},
      year={2020},
      volume={167},
      number={9},
      doi={10.1149/1945-7111/ab9404},
      art_number={090546},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086026731&doi=10.1149%2f1945-7111%2fab9404&partnerID=40&md5=d6716f8c553725a34d99d48c8f6e9b95},
      affiliation={Fraunhofer IKTS, Fraunhofer Institute for Ceramic Technologies and Systems Dresden, Dresden, 01277, Germany; Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={Understanding the diffusion of lithium ions in electrode materials for lithium ion batteries is of great importance for their knowledge-based optimization and development of novel materials and cell designs. The galvanostatic intermittent titration technique (GITT) is widely applied in battery research to study the diffusion of lithium in anode and cathode materials depending on the degree of lithiation. While transport properties of electrode materials at high and ambient temperatures are largely available, low temperature diffusion and rate coefficients are hardly reported in the literature and vary by orders of magnitude for identical active materials. Herein, we demonstrate and discuss several challenges and pitfalls in the application and evaluation of GITT measurements for determining the effective chemical lithium ion diffusion coefficient in lithium insertion electrodes, which become especially important at low temperature. This includes theoretical considerations and an experimental analysis of the promising cathode material LiNi0.5Co0.2Mn0.3O2 (NCM523) in the wide temperature range of -40 °C to 40 °C. We show how the choice of experimental conditions for the GITT measurements and of the subsequent mathematical evaluation significantly influence the derived diffusion coefficient. The results suggest that the large scattering of reported values of the diffusion coefficient could be caused by the use of different evaluation procedures. Simple calculation methods appear to be less suited the lower the temperature is. It is shown that the complementary use of GITT and EIS supplemented by detailed knowledge of the microstructure of the electrode significantly improves the accuracy of determining the diffusion coefficient. © 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.},
      document_type={Article},
      source={Scopus},
      }

  • Phase-field modeling of crack branching and deflection in heterogeneous media
    • A. C. Hansen-Dörr, F. Dammaß, R. de Borst, M. Kästner
    • Engineering Fracture Mechanics , 107004 (2020)
    • DOI   Abstract  

      This contribution presents a diffuse framework for modeling cracks in heterogeneous media. Interfaces are depicted by static phase-fields. This concept allows the use of non-conforming meshes. Another phase-field is used to describe the crack evolution in a regularized manner. The interface modeling implements two combined approaches. Firstly, a method from the literature is extended where the interface is incorporated by a local reduction of the fracture toughness. Secondly, variations of the elastic properties across the interface are enabled by approximating the abrupt change between two adjacent subdomains using a hyperbolic tangent function, which alters the elastic material parameters accordingly. The approach is validated qualitatively by means of crack patterns and quantitatively with respect to critical energy release rates with fundamental analytical results from Linear Elastic Fracture Mechanics, where a crack impinges an arbitrarily oriented interface and either branches, gets deflected or experiences no interfacial influence. The model is particularly relevant for phase-field analyses in heterogeneous, possibly complex-shaped solids, where cohesive failure in the constituent materials as well as adhesive failure at interfaces and its quantification play a role. © 2020 Elsevier Ltd

      @ARTICLE{Hansen-Dörr2020,
      author={Hansen-Dörr, A.C. and Dammaß, F. and de Borst, R. and Kästner, M.},
      title={Phase-field modeling of crack branching and deflection in heterogeneous media},
      journal={Engineering Fracture Mechanics},
      year={2020},
      doi={10.1016/j.engfracmech.2020.107004},
      art_number={107004},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084230485&doi=10.1016%2fj.engfracmech.2020.107004&partnerID=40&md5=3db16b36006c74a5d0b40cd35c87af1c},
      affiliation={Institute of Solid Mechanics, TU Dresden, Dresden, 01062, Germany; University of Sheffield, Department of Civil and Structural Engineering, Mappin Street, Sir Frederick Mappin Building, Sheffield, S1 3JD, United Kingdom; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={This contribution presents a diffuse framework for modeling cracks in heterogeneous media. Interfaces are depicted by static phase-fields. This concept allows the use of non-conforming meshes. Another phase-field is used to describe the crack evolution in a regularized manner. The interface modeling implements two combined approaches. Firstly, a method from the literature is extended where the interface is incorporated by a local reduction of the fracture toughness. Secondly, variations of the elastic properties across the interface are enabled by approximating the abrupt change between two adjacent subdomains using a hyperbolic tangent function, which alters the elastic material parameters accordingly. The approach is validated qualitatively by means of crack patterns and quantitatively with respect to critical energy release rates with fundamental analytical results from Linear Elastic Fracture Mechanics, where a crack impinges an arbitrarily oriented interface and either branches, gets deflected or experiences no interfacial influence. The model is particularly relevant for phase-field analyses in heterogeneous, possibly complex-shaped solids, where cohesive failure in the constituent materials as well as adhesive failure at interfaces and its quantification play a role. © 2020 Elsevier Ltd},
      author_keywords={Adhesive failure; Brittle fracture; Diffuse modeling framework; Heterogeneity; Phase-field modeling},
      document_type={Article},
      source={Scopus},
      }

  • Spin-polarized electron transmission in dna-like systems
    • M. A. Sierra, D. Sánchez, R. Gutierrez, G. Cuniberti, F. Domínguez-Adame, E. Díaz
    • Biomolecules 10, 49 (2020)
    • DOI   Abstract  

      The helical distribution of the electronic density in chiral molecules, such as DNA and bacteriorhodopsin, has been suggested to induce a spin–orbit coupling interaction that may lead to the so-called chirality-induced spin selectivity (CISS) effect. Key ingredients for the theoretical modelling are, in this context, the helically shaped potential of the molecule and, concomitantly, a Rashba-like spin–orbit coupling due to the appearance of a magnetic field in the electron reference frame. Symmetries of these models clearly play a crucial role in explaining the observed effect, but a thorough analysis has been largely ignored in the literature. In this work, we present a study of these symmetries and how they can be exploited to enhance chiral-induced spin selectivity in helical molecular systems. c○ 2019 by the authors. Licensee MDPI, Basel, Switzerland.

      @ARTICLE{Sierra2020,
      author={Sierra, M.A. and Sánchez, D. and Gutierrez, R. and Cuniberti, G. and Domínguez-Adame, F. and Díaz, E.},
      title={Spin-polarized electron transmission in dna-like systems},
      journal={Biomolecules},
      year={2020},
      volume={10},
      number={1},
      doi={10.3390/biom10010049},
      art_number={49},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077494423&doi=10.3390%2fbiom10010049&partnerID=40&md5=8c0a862ccfc59c3812d0453ebd176ad6},
      affiliation={Institute for Cross-Disciplinary Physics and Complex Systems IFISC (UIB-CSIC), Palma de Mallorca, E-07122, Spain; Institut für Theoretische Physik (TP4) and Würzburg, Dresden Cluster of Excellence ct.qmat, Universität Würzburg, Würzburg, 97074, Germany; Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; GISC, Departamento de Física de Materiales, Universidad Complutense, Madrid, E-28040, Spain},
      abstract={The helical distribution of the electronic density in chiral molecules, such as DNA and bacteriorhodopsin, has been suggested to induce a spin–orbit coupling interaction that may lead to the so-called chirality-induced spin selectivity (CISS) effect. Key ingredients for the theoretical modelling are, in this context, the helically shaped potential of the molecule and, concomitantly, a Rashba-like spin–orbit coupling due to the appearance of a magnetic field in the electron reference frame. Symmetries of these models clearly play a crucial role in explaining the observed effect, but a thorough analysis has been largely ignored in the literature. In this work, we present a study of these symmetries and how they can be exploited to enhance chiral-induced spin selectivity in helical molecular systems. c○ 2019 by the authors. Licensee MDPI, Basel, Switzerland.},
      author_keywords={Chirality-induced spin selectivity; DNA electronic transport; Helical molecules; Spin polarization; Spin transport},
      document_type={Article},
      source={Scopus},
      }

2019

  • Topological Electronic Structure and Intrinsic Magnetization in MnBi4Te7: A Bi2Te3 Derivative with a Periodic Mn Sublattice
    • R. C. Vidal, A. Zeugner, J. I. Facio, R. Ray, M. H. Haghighi, A. U. B. Wolter, L. T. Corredor Bohorquez, F. Caglieris, S. Moser, T. Figgemeier, T. R. F. Peixoto, H. B. Vasili, M. Valvidares, S. Jung, C. Cacho, A. Alfonsov, K. Mehlawat, V. Kataev, C. Hess, M. Richter, B. Büchner, J. Van Den Brink, M. Ruck, F. Reinert, H. Bentmann, A. Isaeva
    • Physical Review X 91, 041065 (2019)
    • DOI   Abstract  

      Combinations of nontrivial band topology and long-range magnetic order hold promise for realizations of novel spintronic phenomena, such as the quantum anomalous Hall effect and the topological magnetoelectric effect. Following theoretical advances, material candidates are emerging. Yet, so far a compound that combines a band-inverted electronic structure with an intrinsic net magnetization remains unrealized. MnBi2Te4 has been established as the first antiferromagnetic topological insulator and constitutes the progenitor of a modular (Bi2Te3)n(MnBi2Te4) series. Here, for n=1, we confirm a nonstoichiometric composition proximate to MnBi4Te7. We establish an antiferromagnetic state below 13 K followed by a state with a net magnetization and ferromagnetic-like hysteresis below 5 K. Angle-resolved photoemission experiments and density-functional calculations reveal a topologically nontrivial surface state on the MnBi4Te7(0001) surface, analogous to the nonmagnetic parent compound Bi2Te3. Our results establish MnBi4Te7 as the first band-inverted compound with intrinsic net magnetization providing a versatile platform for the realization of magnetic topological states of matter. © 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the „https://creativecommons.org/licenses/by/4.0/“ Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

      @ARTICLE{Vidal2019,
      author={Vidal, R.C. and Zeugner, A. and Facio, J.I. and Ray, R. and Haghighi, M.H. and Wolter, A.U.B. and Corredor Bohorquez, L.T. and Caglieris, F. and Moser, S. and Figgemeier, T. and Peixoto, T.R.F. and Vasili, H.B. and Valvidares, M. and Jung, S. and Cacho, C. and Alfonsov, A. and Mehlawat, K. and Kataev, V. and Hess, C. and Richter, M. and Büchner, B. and Van Den Brink, J. and Ruck, M. and Reinert, F. and Bentmann, H. and Isaeva, A.},
      title={Topological Electronic Structure and Intrinsic Magnetization in MnBi4Te7: A Bi2Te3 Derivative with a Periodic Mn Sublattice},
      journal={Physical Review X},
      year={2019},
      volume={91},
      number={4},
      doi={10.1103/PhysRevX.9.041065},
      art_number={041065},
      note={cited By 31},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078344525&doi=10.1103%2fPhysRevX.9.041065&partnerID=40&md5=12ef5fe541d57037e8aead8afaa91ed0},
      affiliation={Experimental Physics VII, Universität Würzburg, Würzburg, D-97074, Germany; Würzburg-Dresden Cluster of Excellence Ct.qmat, Germany; Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, Dresden, D-01062, Germany; Leibniz IFW Dresden, Helmholtzstraße 20, Dresden, D-01069, Germany; Experimental Physics IV, Universität Würzburg, Würzburg, D-97074, Germany; Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States; ALBA Synchrotron Light Source, Cerdanyola del Valles, E-08290, Spain; Diamond Light Source, Harwell Campus, Didcot, OX11 0DE, United Kingdom; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, D-01062, Germany; Faculty of Physics, Technische Universität Dresden, Dresden, D-01062, Germany; Max Planck Institute for Chemical Physics of Solids, Dresden, D-01187, Germany},
      abstract={Combinations of nontrivial band topology and long-range magnetic order hold promise for realizations of novel spintronic phenomena, such as the quantum anomalous Hall effect and the topological magnetoelectric effect. Following theoretical advances, material candidates are emerging. Yet, so far a compound that combines a band-inverted electronic structure with an intrinsic net magnetization remains unrealized. MnBi2Te4 has been established as the first antiferromagnetic topological insulator and constitutes the progenitor of a modular (Bi2Te3)n(MnBi2Te4) series. Here, for n=1, we confirm a nonstoichiometric composition proximate to MnBi4Te7. We establish an antiferromagnetic state below 13 K followed by a state with a net magnetization and ferromagnetic-like hysteresis below 5 K. Angle-resolved photoemission experiments and density-functional calculations reveal a topologically nontrivial surface state on the MnBi4Te7(0001) surface, analogous to the nonmagnetic parent compound Bi2Te3. Our results establish MnBi4Te7 as the first band-inverted compound with intrinsic net magnetization providing a versatile platform for the realization of magnetic topological states of matter. © 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/" Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.},
      document_type={Article},
      source={Scopus},
      }

  • Closing the gap between atomic-scale lattice deformations and continuum elasticity
    • M. Salvalaglio, A. Voigt, K. R. Elder
    • npj Computational Materials 5, 48 (2019)
    • DOI   Abstract  

      Crystal lattice deformations can be described microscopically by explicitly accounting for the position of atoms or macroscopically by continuum elasticity. In this work, we report on the description of continuous elastic fields derived from an atomistic representation of crystalline structures that also include features typical of the microscopic scale. Analytic expressions for strain components are obtained from the complex amplitudes of the Fourier modes representing periodic lattice positions, which can be generally provided by atomistic modeling or experiments. The magnitude and phase of these amplitudes, together with the continuous description of strains, are able to characterize crystal rotations, lattice deformations, and dislocations. Moreover, combined with the so-called amplitude expansion of the phase-field crystal model, they provide a suitable tool for bridging microscopic to macroscopic scales. This study enables the in-depth analysis of elasticity effects for macroscale and mesoscale systems taking microscopic details into account. © 2019, The Author(s).

      @ARTICLE{Salvalaglio2019,
      author={Salvalaglio, M. and Voigt, A. and Elder, K.R.},
      title={Closing the gap between atomic-scale lattice deformations and continuum elasticity},
      journal={npj Computational Materials},
      year={2019},
      volume={5},
      number={1},
      doi={10.1038/s41524-019-0185-0},
      art_number={48},
      note={cited By 8},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064241842&doi=10.1038%2fs41524-019-0185-0&partnerID=40&md5=eacd101c78c0e78ffe4b7d0daac7ed85},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Department of Physics, Oakland University, Rochester, MI 48309, United States},
      abstract={Crystal lattice deformations can be described microscopically by explicitly accounting for the position of atoms or macroscopically by continuum elasticity. In this work, we report on the description of continuous elastic fields derived from an atomistic representation of crystalline structures that also include features typical of the microscopic scale. Analytic expressions for strain components are obtained from the complex amplitudes of the Fourier modes representing periodic lattice positions, which can be generally provided by atomistic modeling or experiments. The magnitude and phase of these amplitudes, together with the continuous description of strains, are able to characterize crystal rotations, lattice deformations, and dislocations. Moreover, combined with the so-called amplitude expansion of the phase-field crystal model, they provide a suitable tool for bridging microscopic to macroscopic scales. This study enables the in-depth analysis of elasticity effects for macroscale and mesoscale systems taking microscopic details into account. © 2019, The Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Air-stable redox-active nanomagnets with lanthanide spins radical-bridged by a metal–metal bond
    • F. Liu, G. Velkos, D. S. Krylov, L. Spree, M. Zalibera, R. Ray, N. A. Samoylova, C. -H. Chen, M. Rosenkranz, S. Schiemenz, F. Ziegs, K. Nenkov, A. Kostanyan, T. Greber, A. U. B. Wolter, M. Richter, B. Büchner, S. M. Avdoshenko, A. A. Popov
    • Nature Communications 10, 571 (2019)
    • DOI   Abstract  

      Engineering intramolecular exchange interactions between magnetic metal atoms is a ubiquitous strategy for designing molecular magnets. For lanthanides, the localized nature of 4f electrons usually results in weak exchange coupling. Mediating magnetic interactions between lanthanide ions via radical bridges is a fruitful strategy towards stronger coupling. In this work we explore the limiting case when the role of a radical bridge is played by a single unpaired electron. We synthesize an array of air-stable Ln 2 @C 80 (CH 2 Ph) dimetallofullerenes (Ln 2 = Y 2 , Gd 2 , Tb 2 , Dy 2 , Ho 2 , Er 2 , TbY, TbGd) featuring a covalent lanthanide-lanthanide bond. The lanthanide spins are glued together by very strong exchange interactions between 4f moments and a single electron residing on the metal–metal bonding orbital. Tb 2 @C 80 (CH 2 Ph) shows a gigantic coercivity of 8.2 Tesla at 5 K and a high 100-s blocking temperature of magnetization of 25.2 K. The Ln-Ln bonding orbital in Ln 2 @C 80 (CH 2 Ph) is redox active, enabling electrochemical tuning of the magnetism. © 2019, The Author(s).

      @ARTICLE{Liu2019,
      author={Liu, F. and Velkos, G. and Krylov, D.S. and Spree, L. and Zalibera, M. and Ray, R. and Samoylova, N.A. and Chen, C.-H. and Rosenkranz, M. and Schiemenz, S. and Ziegs, F. and Nenkov, K. and Kostanyan, A. and Greber, T. and Wolter, A.U.B. and Richter, M. and Büchner, B. and Avdoshenko, S.M. and Popov, A.A.},
      title={Air-stable redox-active nanomagnets with lanthanide spins radical-bridged by a metal–metal bond},
      journal={Nature Communications},
      year={2019},
      volume={10},
      number={1},
      doi={10.1038/s41467-019-08513-6},
      art_number={571},
      note={cited By 42},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061050303&doi=10.1038%2fs41467-019-08513-6&partnerID=40&md5=394ab0fa0238c7d120442199e0a6c3d4},
      affiliation={Leibniz Institute for Solid State and Materials Research (IFW Dresden), Helmholtzstrasse 20, Dresden, 01069, Germany; Institute of Physical Chemistry and Chemical Physics, Slovak University of Technology, Radlinského 9, Bratislava, 81237, Slovakia; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, D-01062, Germany; Physik-Institut der Universität Zürich, Winterthurerstrasse 190, Zürich, CH-8057, Switzerland},
      abstract={Engineering intramolecular exchange interactions between magnetic metal atoms is a ubiquitous strategy for designing molecular magnets. For lanthanides, the localized nature of 4f electrons usually results in weak exchange coupling. Mediating magnetic interactions between lanthanide ions via radical bridges is a fruitful strategy towards stronger coupling. In this work we explore the limiting case when the role of a radical bridge is played by a single unpaired electron. We synthesize an array of air-stable Ln 2 @C 80 (CH 2 Ph) dimetallofullerenes (Ln 2 = Y 2 , Gd 2 , Tb 2 , Dy 2 , Ho 2 , Er 2 , TbY, TbGd) featuring a covalent lanthanide-lanthanide bond. The lanthanide spins are glued together by very strong exchange interactions between 4f moments and a single electron residing on the metal–metal bonding orbital. Tb 2 @C 80 (CH 2 Ph) shows a gigantic coercivity of 8.2 Tesla at 5 K and a high 100-s blocking temperature of magnetization of 25.2 K. The Ln-Ln bonding orbital in Ln 2 @C 80 (CH 2 Ph) is redox active, enabling electrochemical tuning of the magnetism. © 2019, The Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Tuning the charge flow between Marcus regimes in an organic thin-film device
    • A. Atxabal, T. Arnold, S. Parui, S. Hutsch, E. Zuccatti, R. Llopis, M. Cinchetti, F. Casanova, F. Ortmann, L. E. Hueso
    • Nature Communications 10, 2089 (2019)
    • DOI   Abstract  

      Marcus’s theory of electron transfer, initially formulated six decades ago for redox reactions in solution, is now of great importance for very diverse scientific communities. The molecular scale tunability of electronic properties renders organic semiconductor materials in principle an ideal platform to test this theory. However, the demonstration of charge transfer in different Marcus regions requires a precise control over the driving force acting on the charge carriers. Here, we make use of a three-terminal hot-electron molecular transistor, which lets us access unconventional transport regimes. Thanks to the control of the injection energy of hot carriers in the molecular thin film we induce an effective negative differential resistance state that is a direct consequence of the Marcus Inverted Region. © 2019, The Author(s).

      @ARTICLE{Atxabal2019,
      author={Atxabal, A. and Arnold, T. and Parui, S. and Hutsch, S. and Zuccatti, E. and Llopis, R. and Cinchetti, M. and Casanova, F. and Ortmann, F. and Hueso, L.E.},
      title={Tuning the charge flow between Marcus regimes in an organic thin-film device},
      journal={Nature Communications},
      year={2019},
      volume={10},
      number={1},
      doi={10.1038/s41467-019-10114-2},
      art_number={2089},
      note={cited By 10},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065321068&doi=10.1038%2fs41467-019-10114-2&partnerID=40&md5=b8305a62b43453461e0a07fc3921b7cb},
      affiliation={CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country, Spain; Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; Experimentelle Physik VI, Technische Universität Dortmund, Dortmund, 44221, Germany; IKERBASQUE, Basque Foundation for Science, Bilbao, Basque Country, 48013, Spain; Simbeyond B. V., Eindhoven, AE 5612, Netherlands; IMEC, Kapeldreef 75, Leuven, 3001, Belgium; K. U. Leuven, Arenbergpark 10, Leuven, 3001, Belgium},
      abstract={Marcus’s theory of electron transfer, initially formulated six decades ago for redox reactions in solution, is now of great importance for very diverse scientific communities. The molecular scale tunability of electronic properties renders organic semiconductor materials in principle an ideal platform to test this theory. However, the demonstration of charge transfer in different Marcus regions requires a precise control over the driving force acting on the charge carriers. Here, we make use of a three-terminal hot-electron molecular transistor, which lets us access unconventional transport regimes. Thanks to the control of the injection energy of hot carriers in the molecular thin film we induce an effective negative differential resistance state that is a direct consequence of the Marcus Inverted Region. © 2019, The Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Impact of molecular quadrupole moments on the energy levels at organic heterojunctions
    • M. Schwarze, K. S. Schellhammer, K. Ortstein, J. Benduhn, C. Gaul, A. Hinderhofer, L. Perdigón Toro, R. Scholz, J. Kublitski, S. Roland, M. Lau, C. Poelking, D. Andrienko, G. Cuniberti, F. Schreiber, D. Neher, K. Vandewal, F. Ortmann, K. Leo
    • Nature Communications 10, 2466 (2019)
    • DOI   Abstract  

      The functionality of organic semiconductor devices crucially depends on molecular energies, namely the ionisation energy and the electron affinity. Ionisation energy and electron affinity values of thin films are, however, sensitive to film morphology and composition, making their prediction challenging. In a combined experimental and simulation study on zinc-phthalocyanine and its fluorinated derivatives, we show that changes in ionisation energy as a function of molecular orientation in neat films or mixing ratio in blends are proportional to the molecular quadrupole component along the π-π-stacking direction. We apply these findings to organic solar cells and demonstrate how the electrostatic interactions can be tuned to optimise the energy of the charge-transfer state at the donor−acceptor interface and the dissociation barrier for free charge carrier generation. The confirmation of the correlation between interfacial energies and quadrupole moments for other materials indicates its relevance for small molecules and polymers. © 2019, The Author(s).

      @ARTICLE{Schwarze2019,
      author={Schwarze, M. and Schellhammer, K.S. and Ortstein, K. and Benduhn, J. and Gaul, C. and Hinderhofer, A. and Perdigón Toro, L. and Scholz, R. and Kublitski, J. and Roland, S. and Lau, M. and Poelking, C. and Andrienko, D. and Cuniberti, G. and Schreiber, F. and Neher, D. and Vandewal, K. and Ortmann, F. and Leo, K.},
      title={Impact of molecular quadrupole moments on the energy levels at organic heterojunctions},
      journal={Nature Communications},
      year={2019},
      volume={10},
      number={1},
      doi={10.1038/s41467-019-10435-2},
      art_number={2466},
      note={cited By 28},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066933035&doi=10.1038%2fs41467-019-10435-2&partnerID=40&md5=a01097f7ffffb2ae99e7ca40cb0c1de5},
      affiliation={Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP), Technische Universität Dresden, Dresden, 01069, Germany; Institute for Materials Science, Max-Bergmann Center of Biomaterials and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01069, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, 01069, Germany; Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, Tübingen, 72076, Germany; Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24–25, Potsdam, 14476, Germany; Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany; Instituut voor Materiaalonderzoek (IMO), Hasselt University, Wetenschapspark 1, Diepenbeek, 3590, Belgium},
      abstract={The functionality of organic semiconductor devices crucially depends on molecular energies, namely the ionisation energy and the electron affinity. Ionisation energy and electron affinity values of thin films are, however, sensitive to film morphology and composition, making their prediction challenging. In a combined experimental and simulation study on zinc-phthalocyanine and its fluorinated derivatives, we show that changes in ionisation energy as a function of molecular orientation in neat films or mixing ratio in blends are proportional to the molecular quadrupole component along the π-π-stacking direction. We apply these findings to organic solar cells and demonstrate how the electrostatic interactions can be tuned to optimise the energy of the charge-transfer state at the donor−acceptor interface and the dissociation barrier for free charge carrier generation. The confirmation of the correlation between interfacial energies and quadrupole moments for other materials indicates its relevance for small molecules and polymers. © 2019, The Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Templated dewetting of single-crystal sub-millimeter-long nanowires and on-chip silicon circuits
    • M. Bollani, M. Salvalaglio, A. Benali, M. Bouabdellaoui, M. Naffouti, M. Lodari, S. D. Corato, A. Fedorov, A. Voigt, I. Fraj, L. Favre, J. B. Claude, D. Grosso, G. Nicotra, A. Mio, A. Ronda, I. Berbezier, M. Abbarchi
    • Nature Communications 10, 5632 (2019)
    • DOI   Abstract  

      Large-scale, defect-free, micro- and nano-circuits with controlled inter-connections represent the nexus between electronic and photonic components. However, their fabrication over large scales often requires demanding procedures that are hardly scalable. Here we synthesize arrays of parallel ultra-long (up to 0.75 mm), monocrystalline, silicon-based nano-wires and complex, connected circuits exploiting low-resolution etching and annealing of thin silicon films on insulator. Phase field simulations reveal that crystal faceting and stabilization of the wires against breaking is due to surface energy anisotropy. Wires splitting, inter-connections and direction are independently managed by engineering the dewetting fronts and exploiting the spontaneous formation of kinks. Finally, we fabricate field-effect transistors with state-of-the-art trans-conductance and electron mobility. Beyond the first experimental evidence of controlled dewetting of patches featuring a record aspect ratio of ~ 1/60000 and self-assembled ~ mm long nano-wires, our method constitutes a distinct and promising approach for the deterministic implementation of atomically-smooth, mono-crystalline electronic and photonic circuits. © 2019, The Author(s).

      @ARTICLE{Bollani2019,
      author={Bollani, M. and Salvalaglio, M. and Benali, A. and Bouabdellaoui, M. and Naffouti, M. and Lodari, M. and Corato, S.D. and Fedorov, A. and Voigt, A. and Fraj, I. and Favre, L. and Claude, J.B. and Grosso, D. and Nicotra, G. and Mio, A. and Ronda, A. and Berbezier, I. and Abbarchi, M.},
      title={Templated dewetting of single-crystal sub-millimeter-long nanowires and on-chip silicon circuits},
      journal={Nature Communications},
      year={2019},
      volume={10},
      number={1},
      doi={10.1038/s41467-019-13371-3},
      art_number={5632},
      note={cited By 11},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076404860&doi=10.1038%2fs41467-019-13371-3&partnerID=40&md5=564823e6155ab37e22a4cdcc0d98931c},
      affiliation={Istituto di Fotonica e Nanotecnologie-Consiglio Nazionale delle Ricerche, Laboratory for Nanostructure Epitaxy and Spintronics on Silicon, LNESS, Via Anzani 42, Como, 22100, Italy; Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Aix Marseille Univ, Université de Toulon, CNRS, Marseille, IM2NP, France; Laboratory of Physics of Condensed Matter and Renewable Energy, Faculty of Sciences and Technology, Hassan II University of Casablanca, 146 Mohammedia, Casablanca, Morocco; Laboratoire de Micro-Optoélectronique et Nanostructures, Faculté des Sciences de Monastir, Université de Monastir, Monastir, 5019, Tunisia; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; CNR-IMM, Zona Industriale Strada VIII, 5, Catania, 95121, Italy},
      abstract={Large-scale, defect-free, micro- and nano-circuits with controlled inter-connections represent the nexus between electronic and photonic components. However, their fabrication over large scales often requires demanding procedures that are hardly scalable. Here we synthesize arrays of parallel ultra-long (up to 0.75 mm), monocrystalline, silicon-based nano-wires and complex, connected circuits exploiting low-resolution etching and annealing of thin silicon films on insulator. Phase field simulations reveal that crystal faceting and stabilization of the wires against breaking is due to surface energy anisotropy. Wires splitting, inter-connections and direction are independently managed by engineering the dewetting fronts and exploiting the spontaneous formation of kinks. Finally, we fabricate field-effect transistors with state-of-the-art trans-conductance and electron mobility. Beyond the first experimental evidence of controlled dewetting of patches featuring a record aspect ratio of ~ 1/60000 and self-assembled ~ mm long nano-wires, our method constitutes a distinct and promising approach for the deterministic implementation of atomically-smooth, mono-crystalline electronic and photonic circuits. © 2019, The Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Stacks of Azobenzene Stars: Self-Assembly Scenario and Stabilising Forces Quantified in Computer Modelling
    • V. Savchenko, M. Koch, A. S. Pavlov, M. Saphiannikova, O. Guskova
    • Molecules (Basel, Switzerland) 24(2019)
    • DOI   Abstract  

      In this paper, the columnar supramolecular aggregates of photosensitive star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core and azobenzene arms are analyzed theoretically by applying a combination of computer simulation techniques. Without a light stimulus, the azobenzene arms adopt the trans-state and build one-dimensional columns of stacked molecules during the first stage of the noncovalent association. These columnar aggregates represent the structural elements of more complex experimentally observed morphologies-fibers, spheres, gels, and others. Here, we determine the most favorable mutual orientations of the trans-stars in the stack in terms of (i) the π – π distance between the cores lengthwise the aggregate, (ii) the lateral displacements due to slippage and (iii) the rotation promoting the helical twist and chirality of the aggregate. To this end, we calculate the binding energy diagrams using density functional theory. The model predictions are further compared with available experimental data. The intermolecular forces responsible for the stability of the stacks in crystals are quantified using Hirshfeld surface analysis. Finally, to characterize the self-assembly mechanism of the stars in solution, we calculate the hydrogen bond lengths, the normalized dipole moments and the binding energies as functions of the columnar length. For this, molecular dynamics trajectories are analyzed. Finally, we conclude about the cooperative nature of the self-assembly of star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core in aqueous solution.

      @ARTICLE{Savchenko2019,
      author={Savchenko, V. and Koch, M. and Pavlov, A.S. and Saphiannikova, M. and Guskova, O.},
      title={Stacks of Azobenzene Stars: Self-Assembly Scenario and Stabilising Forces Quantified in Computer Modelling},
      journal={Molecules (Basel, Switzerland)},
      year={2019},
      volume={24},
      number={23},
      doi={10.3390/molecules24234387},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076144209&doi=10.3390%2fmolecules24234387&partnerID=40&md5=9dd3baed603fe54554c78ce6df9e37e4},
      affiliation={Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, 01069, Germany; Department of Physical Chemistry, Faculty of Chemistry and Technology, Tver State University, Sadovyj per. 35, Tver, 170002, Russian Federation},
      abstract={In this paper, the columnar supramolecular aggregates of photosensitive star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core and azobenzene arms are analyzed theoretically by applying a combination of computer simulation techniques. Without a light stimulus, the azobenzene arms adopt the trans-state and build one-dimensional columns of stacked molecules during the first stage of the noncovalent association. These columnar aggregates represent the structural elements of more complex experimentally observed morphologies-fibers, spheres, gels, and others. Here, we determine the most favorable mutual orientations of the trans-stars in the stack in terms of (i) the π - π distance between the cores lengthwise the aggregate, (ii) the lateral displacements due to slippage and (iii) the rotation promoting the helical twist and chirality of the aggregate. To this end, we calculate the binding energy diagrams using density functional theory. The model predictions are further compared with available experimental data. The intermolecular forces responsible for the stability of the stacks in crystals are quantified using Hirshfeld surface analysis. Finally, to characterize the self-assembly mechanism of the stars in solution, we calculate the hydrogen bond lengths, the normalized dipole moments and the binding energies as functions of the columnar length. For this, molecular dynamics trajectories are analyzed. Finally, we conclude about the cooperative nature of the self-assembly of star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core in aqueous solution.},
      author_keywords={azobenzenes; computer simulations; cooperativity; hydrogen bonding; self-assembly},
      document_type={Article},
      source={Scopus},
      }

  • Do Columns of Azobenzene Stars Disassemble under Light Illumination?
    • M. Koch, M. Saphiannikova, O. Guskova
    • Langmuir 35, 14659-14669 (2019)
    • DOI   Abstract  

      The clustering properties of star-shaped molecules comprising three photochromic azobenzene-containing arms are investigated with specific focus on the influence of light on these structures. Previous experimental works report self-assembly of azobenzene stars in aqueous solution into long columnar clusters that are detectable using optical microscopy. These clusters appear to vanish under UV irradiation, which is known to induce trans-to-cis photoisomerization of the azobenzene groups. We have performed MD simulations, density functional theory, and density functional tight binding calculations to determine conformational properties and binding energies of these clusters. Our simulation data suggest that the binding strength of the clusters is large enough to prevent a breaking along their main axis. We conclude that very likely other mechanisms lead to the apparent disappearance of the clusters. Copyright © 2019 American Chemical Society.

      @ARTICLE{Koch201914659,
      author={Koch, M. and Saphiannikova, M. and Guskova, O.},
      title={Do Columns of Azobenzene Stars Disassemble under Light Illumination?},
      journal={Langmuir},
      year={2019},
      volume={35},
      number={45},
      pages={14659-14669},
      doi={10.1021/acs.langmuir.9b02960},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074614079&doi=10.1021%2facs.langmuir.9b02960&partnerID=40&md5=485eb361f6e6f52349ff0c5d06c02598},
      affiliation={Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={The clustering properties of star-shaped molecules comprising three photochromic azobenzene-containing arms are investigated with specific focus on the influence of light on these structures. Previous experimental works report self-assembly of azobenzene stars in aqueous solution into long columnar clusters that are detectable using optical microscopy. These clusters appear to vanish under UV irradiation, which is known to induce trans-to-cis photoisomerization of the azobenzene groups. We have performed MD simulations, density functional theory, and density functional tight binding calculations to determine conformational properties and binding energies of these clusters. Our simulation data suggest that the binding strength of the clusters is large enough to prevent a breaking along their main axis. We conclude that very likely other mechanisms lead to the apparent disappearance of the clusters. Copyright © 2019 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Chirality-Induced Spin Selectivity in a Coarse-Grained Tight-Binding Model for Helicene
    • M. Geyer, R. Gutierrez, V. Mujica, G. Cuniberti
    • Journal of Physical Chemistry C 123, 27230-27241 (2019)
    • DOI   Abstract  

      Spin-dependent effects in helical molecular systems, leading to the so-called chirality-induced spin selectivity (CISS) effect, have strongly attracted the attention of the chemical and physical community over the past few years. A large amount of experimental material has been collected so far, and different theoretical approaches have been presented to rationalize the CISS effect. The problem is, however, still a subject of debate. We present a semianalytical coarse-grained atomistic description of the electronic structure of a simple helical molecule, including spin-orbit interactions. For reference, we consider helicene, which is a pure carbon-based helical system with no chiral centers, and which has been previously shown experimentally to display a CISS effect. Our model exploits perturbation theory and a Löwdin-like partitioning to obtain an effective Ï-πHamiltonian, where all coupling coefficients depend on the helical geometry and predefined Slater-Koster parameters. As a result, they can be explicitly computed, thus providing physically meaningful orders of magnitude. We further discuss the conditions under which a nonvanishing spin polarization can be obtained in the model. We expect that our approach will serve to bridge the gap between purely phenomenological model Hamiltonians and more advanced first-principles methodologies. © 2019 American Chemical Society.

      @ARTICLE{Geyer201927230,
      author={Geyer, M. and Gutierrez, R. and Mujica, V. and Cuniberti, G.},
      title={Chirality-Induced Spin Selectivity in a Coarse-Grained Tight-Binding Model for Helicene},
      journal={Journal of Physical Chemistry C},
      year={2019},
      volume={123},
      number={44},
      pages={27230-27241},
      doi={10.1021/acs.jpcc.9b07764},
      note={cited By 13},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074425094&doi=10.1021%2facs.jpcc.9b07764&partnerID=40&md5=bee32c668babece8f94d0f3060bbe43b},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, United States; Donostia International Physics Center, P.K. 1072, Donostia, Euskadi, 20080, Spain},
      abstract={Spin-dependent effects in helical molecular systems, leading to the so-called chirality-induced spin selectivity (CISS) effect, have strongly attracted the attention of the chemical and physical community over the past few years. A large amount of experimental material has been collected so far, and different theoretical approaches have been presented to rationalize the CISS effect. The problem is, however, still a subject of debate. We present a semianalytical coarse-grained atomistic description of the electronic structure of a simple helical molecule, including spin-orbit interactions. For reference, we consider helicene, which is a pure carbon-based helical system with no chiral centers, and which has been previously shown experimentally to display a CISS effect. Our model exploits perturbation theory and a Löwdin-like partitioning to obtain an effective Ï-πHamiltonian, where all coupling coefficients depend on the helical geometry and predefined Slater-Koster parameters. As a result, they can be explicitly computed, thus providing physically meaningful orders of magnitude. We further discuss the conditions under which a nonvanishing spin polarization can be obtained in the model. We expect that our approach will serve to bridge the gap between purely phenomenological model Hamiltonians and more advanced first-principles methodologies. © 2019 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • An improved Green’s function algorithm applied to quantum transport in carbon nanotubes
    • F. Teichert, A. Zienert, J. Schuster, M. Schreiber
    • Computational Materials Science 169, 109014 (2019)
    • DOI   Abstract  

      The renormalization-decimation algorithm (RDA) of López Sancho et al. is used in quantum transport theory to calculate bulk and surface Green’s functions. We derive an improved version of the RDA for the case of very long quasi one-dimensional unit cells (in transport direction). This covers not only long unit cells but also supercell-like calculations for structures with disorder or defects. In such large systems, short-range interactions lead to sparse real-space Hamiltonian matrices. We show how this and a corresponding subdivision of the unit cell in combination with the decimation technique can be used to reduce the calculation time. Within the resulting algorithm, separate RDA calculations of much smaller effective Hamiltonian matrices must be done for each Green’s function, which enables the treatment of systems too large for the common RDA. Finally, we discuss the performance properties of our improved algorithm as well as some exemplary results for chiral carbon nanotubes. © 2019 Elsevier B.V.

      @ARTICLE{Teichert2019,
      author={Teichert, F. and Zienert, A. and Schuster, J. and Schreiber, M.},
      title={An improved Green's function algorithm applied to quantum transport in carbon nanotubes},
      journal={Computational Materials Science},
      year={2019},
      volume={169},
      doi={10.1016/j.commatsci.2019.05.012},
      art_number={109014},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070532970&doi=10.1016%2fj.commatsci.2019.05.012&partnerID=40&md5=75f2e03dd4d7ec0fdb6138470a54e653},
      affiliation={Institute of Physics, Chemnitz University of Technology, Chemnitz, 09107, Germany; Center for Microtechnologies, Chemnitz University of Technology, Chemnitz, 09107, Germany; Fraunhofer Institute for Electronic Nano Systems (ENAS), Chemnitz, 09126, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={The renormalization-decimation algorithm (RDA) of López Sancho et al. is used in quantum transport theory to calculate bulk and surface Green's functions. We derive an improved version of the RDA for the case of very long quasi one-dimensional unit cells (in transport direction). This covers not only long unit cells but also supercell-like calculations for structures with disorder or defects. In such large systems, short-range interactions lead to sparse real-space Hamiltonian matrices. We show how this and a corresponding subdivision of the unit cell in combination with the decimation technique can be used to reduce the calculation time. Within the resulting algorithm, separate RDA calculations of much smaller effective Hamiltonian matrices must be done for each Green's function, which enables the treatment of systems too large for the common RDA. Finally, we discuss the performance properties of our improved algorithm as well as some exemplary results for chiral carbon nanotubes. © 2019 Elsevier B.V.},
      author_keywords={Carbon nanotube (CNT); Electronic transport; Renormalization-decimation algorithm (RDA)},
      document_type={Article},
      source={Scopus},
      }

  • Numerical and Experimental Study of the Spatial Stress Distribution on the Cornea Surface During a Non-Contact Tonometry Examination
    • S. Muench, M. Roellig, E. Spoerl, D. Balzani
    • Experimental Mechanics 59, 1285-1297 (2019)
    • DOI   Abstract  

      The determination of biomechanical properties of the cornea by a non-contact tonometry (NCT) examination requires a precise knowledge of the air puff generated in the device, which is applied to the cornea surface. In this study, a method is proposed to identify the resulting stress profile on the surface, which may be used to numerically solve an inverse problem to obtain the material properties. This method is based on an experimental characterization of the air puff created by the Corvis ST in combination with computational fluid dynamic (CFD) simulations, which are adjusted to the experimental data. The identified nozzle inlet pressure of approximately 25 kPa (188.5mmHg) is then used for a numerical influence study of the interaction between the air puff and the cornea deformation. Therefore, eleven cornea deformation states based on measurements are implemented in the CFD model. A more realistic model is also analyzed by the geometrical reproduction of the human face, which is used for a further influence study. The outcomes showed a dependence between the cornea deformation and the pressure as well as the shear stress distribution. However, quantitatively, the shear stress component can be considered of minor importance being approximately one hundred times smaller than the pressure. The examination with consideration of the human face demonstrates that the pressure and shear stress distributions are not rotationally symmetric in measurements on real humans, which indicates the requirement to include more complex stress distributions on the eye. We present the detailed stress distribution on the cornea during a non-contact tonometry examination, which is made accessible for further investigations in the future by analytical nonlinear functions. © 2018, Society for Experimental Mechanics.

      @ARTICLE{Muench20191285,
      author={Muench, S. and Roellig, M. and Spoerl, E. and Balzani, D.},
      title={Numerical and Experimental Study of the Spatial Stress Distribution on the Cornea Surface During a Non-Contact Tonometry Examination},
      journal={Experimental Mechanics},
      year={2019},
      volume={59},
      number={9},
      pages={1285-1297},
      doi={10.1007/s11340-018-00449-0},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058390192&doi=10.1007%2fs11340-018-00449-0&partnerID=40&md5=984b0e407ea5c2142edd819fc9848e3e},
      affiliation={Institute of Mechanics and Shell Structures (IMF), Dresden, 01062, Germany; Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), Dresden, 01109, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Department of Ophthalmology, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, 01307, Germany; Chair of Computational Mechanics, Ruhr-Universität Bochum, Bochum, 44801, Germany},
      abstract={The determination of biomechanical properties of the cornea by a non-contact tonometry (NCT) examination requires a precise knowledge of the air puff generated in the device, which is applied to the cornea surface. In this study, a method is proposed to identify the resulting stress profile on the surface, which may be used to numerically solve an inverse problem to obtain the material properties. This method is based on an experimental characterization of the air puff created by the Corvis ST in combination with computational fluid dynamic (CFD) simulations, which are adjusted to the experimental data. The identified nozzle inlet pressure of approximately 25 kPa (188.5mmHg) is then used for a numerical influence study of the interaction between the air puff and the cornea deformation. Therefore, eleven cornea deformation states based on measurements are implemented in the CFD model. A more realistic model is also analyzed by the geometrical reproduction of the human face, which is used for a further influence study. The outcomes showed a dependence between the cornea deformation and the pressure as well as the shear stress distribution. However, quantitatively, the shear stress component can be considered of minor importance being approximately one hundred times smaller than the pressure. The examination with consideration of the human face demonstrates that the pressure and shear stress distributions are not rotationally symmetric in measurements on real humans, which indicates the requirement to include more complex stress distributions on the eye. We present the detailed stress distribution on the cornea during a non-contact tonometry examination, which is made accessible for further investigations in the future by analytical nonlinear functions. © 2018, Society for Experimental Mechanics.},
      author_keywords={Air puff characterization; Computational fluid dynamics; Corneal biomechanics; Non-contact tonometry; Pressure distribution; Shear force distribution},
      document_type={Article},
      source={Scopus},
      }

  • Large off-diagonal exchange couplings and spin liquid states in C3-symmetric iridates
    • R. Yadav, S. Nishimoto, M. Richter, J. Van Den Brink, R. Ray
    • Physical Review B 100, 144422 (2019)
    • DOI   Abstract  

      Iridate oxides on a honeycomb lattice are considered promising candidates for realization of quantum spin liquid states. We investigate the magnetic couplings in a structural model for a honeycomb iridate K2IrO3, with C3 point-group symmetry at the Ir sites, which is an end member of the recently synthesized iridate family KxIryO2. Using ab initio quantum chemical methods, we elucidate the subtle relationship between the real space symmetry and magnetic anisotropy and show that the higher point-group symmetry leads to high frustration with strong magnetic anisotropy driven by the unusually large off-diagonal exchange couplings (Γ’s) as opposed to other spin-liquid candidates considered so far. Consequently, large quantum fluctuations imply lack of magnetic ordering consistent with the experiments. Exact diagonalization calculations for the fully anisotropic K-J-Γ Hamiltonian reveal the importance of the off-diagonal anisotropic exchange couplings in stabilizing a spin liquid state and highlight an alternative route to stabilize spin liquid states for ferromagnetic K. © 2019 American Physical Society.

      @ARTICLE{Yadav2019,
      author={Yadav, R. and Nishimoto, S. and Richter, M. and Van Den Brink, J. and Ray, R.},
      title={Large off-diagonal exchange couplings and spin liquid states in C3-symmetric iridates},
      journal={Physical Review B},
      year={2019},
      volume={100},
      number={14},
      doi={10.1103/PhysRevB.100.144422},
      art_number={144422},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074432597&doi=10.1103%2fPhysRevB.100.144422&partnerID=40&md5=bd46df97e692dba56d336f0ee9af28ff},
      affiliation={IFW Dresden, Helmholtzstrasse 20, Dresden, D-01069, Germany; Department of Physics, TU Dresden, Dresden, D-01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, D-01062, Germany},
      abstract={Iridate oxides on a honeycomb lattice are considered promising candidates for realization of quantum spin liquid states. We investigate the magnetic couplings in a structural model for a honeycomb iridate K2IrO3, with C3 point-group symmetry at the Ir sites, which is an end member of the recently synthesized iridate family KxIryO2. Using ab initio quantum chemical methods, we elucidate the subtle relationship between the real space symmetry and magnetic anisotropy and show that the higher point-group symmetry leads to high frustration with strong magnetic anisotropy driven by the unusually large off-diagonal exchange couplings (Γ's) as opposed to other spin-liquid candidates considered so far. Consequently, large quantum fluctuations imply lack of magnetic ordering consistent with the experiments. Exact diagonalization calculations for the fully anisotropic K-J-Γ Hamiltonian reveal the importance of the off-diagonal anisotropic exchange couplings in stabilizing a spin liquid state and highlight an alternative route to stabilize spin liquid states for ferromagnetic K. © 2019 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Deterministic three-dimensional self-assembly of Si through a rimless and topology-preserving dewetting regime
    • M. Naffouti, M. Salvalaglio, T. David, J. -B. Claude, M. Bollani, A. Voigt, A. Benkouider, L. Favre, A. Ronda, I. Berbezier, A. Delobbe, A. Houel, M. Abbarchi
    • Physical Review Materials 3, 103402 (2019)
    • DOI   Abstract  

      Capillary-driven mass transport in solids is typically understood in terms of surface-diffusion limited kinetics, leading to conventional solid-state dewetting of thin films. However, another mass transport mechanism, so-called surface-attachment/detachment limited kinetics, is possible. It can shrink a solid film, preserving its original topology without breaking it in isolated islands, and leads to faster dynamics for smaller film curvature in contrast with the opposite behavior observed for surface-diffusion limited kinetics. In this work, we present a rimless dewetting regime for Si, which is ascribed to effective attachment-limited kinetics mediated by the coexistence of crystalline and amorphous Si phases. Phase-field numerical simulations quantitatively reproduce the experimental observations, assessing the main mass transport mechanism at play. The process can be exploited to obtain in a deterministic fashion monocrystalline islands (with 95% probability) pinned at ≈500 nm from a hole milled within closed patches. © 2019 American Physical Society.

      @ARTICLE{Naffouti2019,
      author={Naffouti, M. and Salvalaglio, M. and David, T. and Claude, J.-B. and Bollani, M. and Voigt, A. and Benkouider, A. and Favre, L. and Ronda, A. and Berbezier, I. and Delobbe, A. and Houel, A. and Abbarchi, M.},
      title={Deterministic three-dimensional self-assembly of Si through a rimless and topology-preserving dewetting regime},
      journal={Physical Review Materials},
      year={2019},
      volume={3},
      number={10},
      doi={10.1103/PhysRevMaterials.3.103402},
      art_number={103402},
      note={cited By 2},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073456787&doi=10.1103%2fPhysRevMaterials.3.103402&partnerID=40&md5=fc34950d0caf7ae32d536d350f93055f},
      affiliation={Aix Marseille Université, Université de Toulon, CNRS, IM2NP, Marseille, France; Laboratoire de Micro-Optoélectronique et Nanostructures, Faculté des Sciences, Monastir Université de Monastir, Monastir, 5019, Tunisia; Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Istituto di Fotonica e Nanotecnologie-Consiglio Nazionale Delle Ricerche, Laboratory for Nanostructure Epitaxy and Spintronics on Silicon, Via Anzani 42, Como, 22100, Italy; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; Orsay Physics, Fuveau, 13710, France},
      abstract={Capillary-driven mass transport in solids is typically understood in terms of surface-diffusion limited kinetics, leading to conventional solid-state dewetting of thin films. However, another mass transport mechanism, so-called surface-attachment/detachment limited kinetics, is possible. It can shrink a solid film, preserving its original topology without breaking it in isolated islands, and leads to faster dynamics for smaller film curvature in contrast with the opposite behavior observed for surface-diffusion limited kinetics. In this work, we present a rimless dewetting regime for Si, which is ascribed to effective attachment-limited kinetics mediated by the coexistence of crystalline and amorphous Si phases. Phase-field numerical simulations quantitatively reproduce the experimental observations, assessing the main mass transport mechanism at play. The process can be exploited to obtain in a deterministic fashion monocrystalline islands (with 95% probability) pinned at ≈500 nm from a hole milled within closed patches. © 2019 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Recapitulating bone development events in a customised bioreactor through interplay of oxygen tension, medium pH, and systematic differentiation approaches
    • P. S. Lee, R. Hess, J. Friedrichs, V. Haenchen, H. Eckert, G. Cuniberti, D. Rancourt, R. Krawetz, V. Hintze, M. Gelinsky, D. Scharnweber
    • Journal of Tissue Engineering and Regenerative Medicine 13, 1672-1684 (2019)
    • DOI   Abstract  

      Bone development and homeostasis are intricate processes that require co-existence and dynamic interactions among multiple cell types. However, controlled dynamic niches that derive and support stable propagation of these cells from single stem cell source is not sustainable in conventional culturing vessels. In bioreactor cultures that support dynamic niches, the limited source and stability of growth factors are often a major limiting factor for long-term in vitro cultures. Hence, alternative growth factor-free differentiation approaches are designed and their efficacy to achieve different osteochondral cell types is investigated. Briefly, a dynamic niche is achieved by varying medium pH, oxygen tension (pO2) distribution in bioreactor, initiating chondrogenic differentiation with chondroitin sulphate A (CSA), and implementing systematic differentiation regimes. In this study, we demonstrated that CSA is a potent chondrogenic inducer, specifically in combination with acidic medium and low pO2. Further, endochondral ossification is recapitulated through a systematic chondrogenic–osteogenic (ch-os) differentiation regime, and multiple osteochondral cell types are derived. Chondrogenic hypertrophy was also enhanced specifically in high pO2 regions. Consequently, mineralised constructs with higher structural integrity, volume, and tailored dimensions are achieved. In contrast, a continuous osteogenic differentiation regime (os-os) has derived compact and dense constructs, whereas a continuous chondrogenic differentiation regime (ch-ch) has attenuated construct mineralisation and impaired development. In conclusion, a growth factor-free differentiation approach is achieved through interplay of pO2, medium pH, and systematic differentiation regimes. The controlled dynamic niches have recapitulated endochondral ossification and can potentially be exploited to derive larger bone constructs with near physiological properties. © 2019 John Wiley & Sons, Ltd.

      @ARTICLE{Lee20191672,
      author={Lee, P.S. and Hess, R. and Friedrichs, J. and Haenchen, V. and Eckert, H. and Cuniberti, G. and Rancourt, D. and Krawetz, R. and Hintze, V. and Gelinsky, M. and Scharnweber, D.},
      title={Recapitulating bone development events in a customised bioreactor through interplay of oxygen tension, medium pH, and systematic differentiation approaches},
      journal={Journal of Tissue Engineering and Regenerative Medicine},
      year={2019},
      volume={13},
      number={9},
      pages={1672-1684},
      doi={10.1002/term.2921},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85069914153&doi=10.1002%2fterm.2921&partnerID=40&md5=cde5d1947084e9e0b5647b56dd619166},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, Germany; Leibniz Institute of Polymer Research Dresden e. V., Dresden, Germany; Department of Pediatrics, Medizinische Fakultät Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, Germany; Department of Cell Biology and Anatomy, Faculty of Medicine, University of Calgary, Calgary, AB, Canada; Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, AB, Canada; Center for Translational Bone, Joint and Soft Tissue Research, Technische Universität Dresden, Dresden, Germany},
      abstract={Bone development and homeostasis are intricate processes that require co-existence and dynamic interactions among multiple cell types. However, controlled dynamic niches that derive and support stable propagation of these cells from single stem cell source is not sustainable in conventional culturing vessels. In bioreactor cultures that support dynamic niches, the limited source and stability of growth factors are often a major limiting factor for long-term in vitro cultures. Hence, alternative growth factor-free differentiation approaches are designed and their efficacy to achieve different osteochondral cell types is investigated. Briefly, a dynamic niche is achieved by varying medium pH, oxygen tension (pO2) distribution in bioreactor, initiating chondrogenic differentiation with chondroitin sulphate A (CSA), and implementing systematic differentiation regimes. In this study, we demonstrated that CSA is a potent chondrogenic inducer, specifically in combination with acidic medium and low pO2. Further, endochondral ossification is recapitulated through a systematic chondrogenic–osteogenic (ch-os) differentiation regime, and multiple osteochondral cell types are derived. Chondrogenic hypertrophy was also enhanced specifically in high pO2 regions. Consequently, mineralised constructs with higher structural integrity, volume, and tailored dimensions are achieved. In contrast, a continuous osteogenic differentiation regime (os-os) has derived compact and dense constructs, whereas a continuous chondrogenic differentiation regime (ch-ch) has attenuated construct mineralisation and impaired development. In conclusion, a growth factor-free differentiation approach is achieved through interplay of pO2, medium pH, and systematic differentiation regimes. The controlled dynamic niches have recapitulated endochondral ossification and can potentially be exploited to derive larger bone constructs with near physiological properties. © 2019 John Wiley & Sons, Ltd.},
      author_keywords={bone development; murine embryonic stem cells; nodules; perfusion bioreactor; stem cell differentiation; tissue engineering},
      document_type={Article},
      source={Scopus},
      }

  • Towards reconfigurable electronics: Silicidation of top-down fabricated silicon nanowires
    • M. B. Khan, D. Deb, J. Kerbusch, F. Fuchs, M. Löffler, S. Banerjee, U. Mühle, W. M. Weber, S. Gemming, J. Schuster, A. Erbe, Y. M. Georgiev
    • Applied Sciences (Switzerland) 9, 3462 (2019)
    • DOI   Abstract  

      We present results of our investigations on nickel silicidation of top-down fabricated silicon nanowires (SiNWs). Control over the silicidation process is important for the application of SiNWs in reconfigurable field-effect transistors. Silicidation is performed using a rapid thermal annealing process on the SiNWs fabricated by electron beam lithography and inductively-coupled plasma etching. The effects of variations in crystallographic orientations of SiNWs and different NW designs on the silicidation process are studied. Scanning electron microscopy and transmission electron microscopy are performed to study Ni diffusion, silicide phases, and silicide-silicon interfaces. Control over the silicide phase is achieved together with atomically sharp silicide-silicon interfaces. We find that (111) interfaces are predominantly formed, which are energetically most favorable according to density functional theory calculations. However, control over the silicide length remains a challenge. © 2019 by the authors.

      @ARTICLE{Khan2019,
      author={Khan, M.B. and Deb, D. and Kerbusch, J. and Fuchs, F. and Löffler, M. and Banerjee, S. and Mühle, U. and Weber, W.M. and Gemming, S. and Schuster, J. and Erbe, A. and Georgiev, Y.M.},
      title={Towards reconfigurable electronics: Silicidation of top-down fabricated silicon nanowires},
      journal={Applied Sciences (Switzerland)},
      year={2019},
      volume={9},
      number={17},
      doi={10.3390/app9173462},
      art_number={3462},
      note={cited By 4},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072286808&doi=10.3390%2fapp9173462&partnerID=40&md5=4ea9fddcb7650e0573fe0f703fd65541},
      affiliation={Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, 01328, Germany; International Helmholtz Research School for Nanoelectronic Network, HZDR, Dresden, 01328, Germany; Center for Advancing Electronics Dresden, Dresden University of Technology, Dresden, 01062, Germany; Institute of Physics, Chemnitz University of Technology, Chemitz, 09126, Germany; Fraunhofer Institute for Electronic Nano Systems, Chemnitz, 09126, Germany; Dresden Center for Nano-Analysis, Dresden University of Technology, Dresden, 01062, Germany; Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Dresden, Dresden, 01277, Germany; Namlab gGmbH, Nöthnitzer Strasse 64, Dresden, 01187, Germany; Dresden Center for Computational Materials Science, Dresden University of Technology, Dresden, 01062, Germany; On leave of absence from the Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chausse Blvd., Sofia, 1784, Bulgaria},
      abstract={We present results of our investigations on nickel silicidation of top-down fabricated silicon nanowires (SiNWs). Control over the silicidation process is important for the application of SiNWs in reconfigurable field-effect transistors. Silicidation is performed using a rapid thermal annealing process on the SiNWs fabricated by electron beam lithography and inductively-coupled plasma etching. The effects of variations in crystallographic orientations of SiNWs and different NW designs on the silicidation process are studied. Scanning electron microscopy and transmission electron microscopy are performed to study Ni diffusion, silicide phases, and silicide-silicon interfaces. Control over the silicide phase is achieved together with atomically sharp silicide-silicon interfaces. We find that (111) interfaces are predominantly formed, which are energetically most favorable according to density functional theory calculations. However, control over the silicide length remains a challenge. © 2019 by the authors.},
      author_keywords={Annealing; Field-effect transistors; Nickel silicide; Schottky junction},
      document_type={Article},
      source={Scopus},
      }

  • Direct Assembly and Metal-Ion Binding Properties of Oxytocin Monolayer on Gold Surfaces
    • E. Mervinetsky, I. Alshanski, J. Buchwald, A. Dianat, I. Lončarić, P. Lazić, Ž. Crljen, R. Gutierrez, G. Cuniberti, M. Hurevich, S. Yitzchaik
    • Langmuir 35, 11114-11122 (2019)
    • DOI   Abstract  

      Peptides are very common recognition entities that are usually attached to surfaces using multistep processes. These processes require modification of the native peptides and of the substrates. Using functional groups in native peptides for their assembly on surfaces without affecting their biological activity can facilitate the preparation of biosensors. Herein, we present a simple single-step formation of native oxytocin monolayer on gold surface. These surfaces were characterized by atomic force spectroscopy, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy. We took advantage of the native disulfide bridge of the oxytocin for anchoring the peptide to the Au surface, while preserving the metal-ion binding properties. Self-assembled oxytocin monolayer was used by electrochemical impedance spectroscopy for metal-ion sensing leading to subnanomolar sensitivities for zinc or copper ions. © 2019 American Chemical Society.

      @ARTICLE{Mervinetsky201911114,
      author={Mervinetsky, E. and Alshanski, I. and Buchwald, J. and Dianat, A. and Lončarić, I. and Lazić, P. and Crljen, Ž. and Gutierrez, R. and Cuniberti, G. and Hurevich, M. and Yitzchaik, S.},
      title={Direct Assembly and Metal-Ion Binding Properties of Oxytocin Monolayer on Gold Surfaces},
      journal={Langmuir},
      year={2019},
      volume={35},
      number={34},
      pages={11114-11122},
      doi={10.1021/acs.langmuir.9b01830},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070943009&doi=10.1021%2facs.langmuir.9b01830&partnerID=40&md5=131acac3dcdb6d6dc46b5163d2f98972},
      affiliation={Institute of Chemistry, Hebrew University of Jerusalem, E. Safra Campus, Jerusalem, 91904, Israel; Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, E. Safra Campus, Jerusalem, 91904, Israel; Institute for Materials Science, Max Bergmann Center of Biomaterials, Hallwachsstraße 3, Dresden, 01062, Germany; Ruder Bošković Institute, Bijenička cesta 54, Zagreb, 10000, Croatia; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Peptides are very common recognition entities that are usually attached to surfaces using multistep processes. These processes require modification of the native peptides and of the substrates. Using functional groups in native peptides for their assembly on surfaces without affecting their biological activity can facilitate the preparation of biosensors. Herein, we present a simple single-step formation of native oxytocin monolayer on gold surface. These surfaces were characterized by atomic force spectroscopy, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy. We took advantage of the native disulfide bridge of the oxytocin for anchoring the peptide to the Au surface, while preserving the metal-ion binding properties. Self-assembled oxytocin monolayer was used by electrochemical impedance spectroscopy for metal-ion sensing leading to subnanomolar sensitivities for zinc or copper ions. © 2019 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Influence of Mesityl and Thiophene Peripheral Substituents on Surface Attachment, Redox Chemistry, and ORR Activity of Molecular Iron Porphyrin Catalysts on Electrodes
    • R. Götz, K. H. Ly, P. Wrzolek, A. Dianat, A. Croy, G. Cuniberti, P. Hildebrandt, M. Schwalbe, I. M. Weidinger
    • Inorganic Chemistry 58, 10637-10647 (2019)
    • DOI   Abstract  

      Two iron porphyrin complexes with either mesityl (FeTMP) or thiophene (FeT3ThP) peripheral substituents were attached to basal pyrolytic graphite and Ag electrodes via different immobilization methods. By combining cyclic voltammetry and in-operando surface-enhanced Raman spectroscopy along with MD simulations and DFT calculations, their respective surface attachment, redox chemistry and activity toward electrocatalytic oxygen reduction was investigated. For both porphyrin complexes, it could be shown that catalytic activity is restricted to the first (few) molecular layer(s), although electrodes covered with thiophene-substituted complexes showed a better capability to consume the oxygen at a given overpotential even in thicker films. The spectroscopic data and simulations suggest that both porphyrin complexes attach to a Ag electrode surface in a way that maximum planarity and minimum distance between the catalytic iron site and the electrode is achieved. However, due to the distinctive design of the FeT3ThP complex, the thiophene rings are capable of occupying a conformation, via rotation around the bonding axis to the porphyrin, in which all four sulfur atoms can coordinate to the Ag surface. This effect creates a dense and planar surface coverage of the porphyrin on the electrode facilitating a fast (multi) electron transfer via several covalent Ag-S bonds. In contrast, bulky mesityl groups as peripheral substituents, which have been initially introduced to prevent aggregation and improve catalytic behavior in solution, exert a negative effect on the overall electrocatalytic performance in the immobilized state as a less dense coverage and less stable interactions with the surface are formed. Our results underline the importance of rationally designed heterogenized molecular catalysts to achieve optimal turnover, which not only strictly applies to the here discussed oxygen reduction reaction but eventually holds also true for other energy conversion reactions such as carbon dioxide reduction. © 2019 American Chemical Society.

      @ARTICLE{Götz201910637,
      author={Götz, R. and Ly, K.H. and Wrzolek, P. and Dianat, A. and Croy, A. and Cuniberti, G. and Hildebrandt, P. and Schwalbe, M. and Weidinger, I.M.},
      title={Influence of Mesityl and Thiophene Peripheral Substituents on Surface Attachment, Redox Chemistry, and ORR Activity of Molecular Iron Porphyrin Catalysts on Electrodes},
      journal={Inorganic Chemistry},
      year={2019},
      volume={58},
      number={16},
      pages={10637-10647},
      doi={10.1021/acs.inorgchem.9b00043},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070966873&doi=10.1021%2facs.inorgchem.9b00043&partnerID=40&md5=02deb939140c634b0a70c5a22ecc3257},
      affiliation={Faculty of Chemistry and Food Chemistry, Dresden University of Technology, Dresden, 01062, Germany; Institute of Chemistry, Humboldt-Universität zu Berlin, Berlin, 12489, Germany; Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden University of Technology, Dresden, 01062, Germany; Center for Advancing Electronics, Dresden Center for Computational Materials Science, Dresden University of Technology, Dresden, 01062, Germany; Institute of Chemistry, Technische Universität Berlin, Berlin, 10623, Germany},
      abstract={Two iron porphyrin complexes with either mesityl (FeTMP) or thiophene (FeT3ThP) peripheral substituents were attached to basal pyrolytic graphite and Ag electrodes via different immobilization methods. By combining cyclic voltammetry and in-operando surface-enhanced Raman spectroscopy along with MD simulations and DFT calculations, their respective surface attachment, redox chemistry and activity toward electrocatalytic oxygen reduction was investigated. For both porphyrin complexes, it could be shown that catalytic activity is restricted to the first (few) molecular layer(s), although electrodes covered with thiophene-substituted complexes showed a better capability to consume the oxygen at a given overpotential even in thicker films. The spectroscopic data and simulations suggest that both porphyrin complexes attach to a Ag electrode surface in a way that maximum planarity and minimum distance between the catalytic iron site and the electrode is achieved. However, due to the distinctive design of the FeT3ThP complex, the thiophene rings are capable of occupying a conformation, via rotation around the bonding axis to the porphyrin, in which all four sulfur atoms can coordinate to the Ag surface. This effect creates a dense and planar surface coverage of the porphyrin on the electrode facilitating a fast (multi) electron transfer via several covalent Ag-S bonds. In contrast, bulky mesityl groups as peripheral substituents, which have been initially introduced to prevent aggregation and improve catalytic behavior in solution, exert a negative effect on the overall electrocatalytic performance in the immobilized state as a less dense coverage and less stable interactions with the surface are formed. Our results underline the importance of rationally designed heterogenized molecular catalysts to achieve optimal turnover, which not only strictly applies to the here discussed oxygen reduction reaction but eventually holds also true for other energy conversion reactions such as carbon dioxide reduction. © 2019 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Straintronics in graphene: Extra large electronic band gap induced by tensile and shear strains
    • I. Y. Sahalianov, T. M. Radchenko, V. A. Tatarenko, G. Cuniberti, Y. I. Prylutskyy
    • Journal of Applied Physics 126, 054302 (2019)
    • DOI   Abstract  

      The possibility of inducing a sizeable energy gap in the electronic structure of a graphene layer is still one of the biggest and most debated challenges in graphene electronics. Despite promising theoretical results, some experimental studies report the absence of a bandgap even in highly mechanically strained graphene. In this paper, we address the main reasons for these discrepancies and study the influence of uniaxial tensile and shear strains as well as their combinations on the eventual bandgap opening in monolayer graphene. Deformation-dependent bandgap diagrams are constructed over a wide range of the strain tensor parameters of up to 26%, which is close to predicted graphene breaking point. The use of a combination of shear strain and uniaxial tensile deformations is found to be the easiest way for bandgap opening and tuning. The results of our numerical calculations demonstrate that shear strains can induce a bandgap of up to 4 eV at the largest elastic deformations, while a combination of shear and uniaxial strains can provide an energy gap of up to 6 eV that is substantially higher than for some materials (including silicon) typically used in nanoelectronic devices. The numerically obtained findings are carefully contrasted with other results available in the literature. © 2019 Author(s).

      @ARTICLE{Sahalianov2019,
      author={Sahalianov, I.Y. and Radchenko, T.M. and Tatarenko, V.A. and Cuniberti, G. and Prylutskyy, Y.I.},
      title={Straintronics in graphene: Extra large electronic band gap induced by tensile and shear strains},
      journal={Journal of Applied Physics},
      year={2019},
      volume={126},
      number={5},
      doi={10.1063/1.5095600},
      art_number={054302},
      note={cited By 23},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073890432&doi=10.1063%2f1.5095600&partnerID=40&md5=ecdafab45cf2f51ccb31e709304eafee},
      affiliation={Linköping University, Norrköping, 60174, Sweden; G. V. Kurdyumov Institute for Metal Physics of the NAS of Ukraine, Kyiv, 03142, Ukraine; Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Taras Shevchenko National University of Kyiv, Kyiv, 03127, Ukraine},
      abstract={The possibility of inducing a sizeable energy gap in the electronic structure of a graphene layer is still one of the biggest and most debated challenges in graphene electronics. Despite promising theoretical results, some experimental studies report the absence of a bandgap even in highly mechanically strained graphene. In this paper, we address the main reasons for these discrepancies and study the influence of uniaxial tensile and shear strains as well as their combinations on the eventual bandgap opening in monolayer graphene. Deformation-dependent bandgap diagrams are constructed over a wide range of the strain tensor parameters of up to 26%, which is close to predicted graphene breaking point. The use of a combination of shear strain and uniaxial tensile deformations is found to be the easiest way for bandgap opening and tuning. The results of our numerical calculations demonstrate that shear strains can induce a bandgap of up to 4 eV at the largest elastic deformations, while a combination of shear and uniaxial strains can provide an energy gap of up to 6 eV that is substantially higher than for some materials (including silicon) typically used in nanoelectronic devices. The numerically obtained findings are carefully contrasted with other results available in the literature. © 2019 Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • A finite element approach for vector- and tensor-valued surface PDEs
    • M. Nestler, I. Nitschke, A. Voigt
    • Journal of Computational Physics 389, 48-61 (2019)
    • DOI   Abstract  

      We derive a Cartesian componentwise description of the covariant derivative of tangential tensor fields of any degree on Riemannian manifolds. This allows to reformulate any vector- and tensor-valued surface PDE in a form suitable to be solved by established tools for scalar-valued surface PDEs. We consider piecewise linear Lagrange surface finite elements on triangulated surfaces and validate the approach by a vector- and a tensor-valued surface Helmholtz problem on an ellipsoid. We experimentally show optimal (linear) order of convergence for these problems. The full functionality is demonstrated by solving a surface Landau-de Gennes problem on the Stanford bunny. All tools required to apply this approach to other vector- and tensor-valued surface PDEs are provided. © 2019 Elsevier Inc.

      @ARTICLE{Nestler201948,
      author={Nestler, M. and Nitschke, I. and Voigt, A.},
      title={A finite element approach for vector- and tensor-valued surface PDEs},
      journal={Journal of Computational Physics},
      year={2019},
      volume={389},
      pages={48-61},
      doi={10.1016/j.jcp.2019.03.006},
      note={cited By 8},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063877402&doi=10.1016%2fj.jcp.2019.03.006&partnerID=40&md5=8bede36a144444ecd1a409499e13050f},
      affiliation={Institut für Wissenschaftliches Rechnen, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Center for Systems Biology Dresden (CSBD), Pfotenhauerstr. 108, Dresden, 01307, Germany},
      abstract={We derive a Cartesian componentwise description of the covariant derivative of tangential tensor fields of any degree on Riemannian manifolds. This allows to reformulate any vector- and tensor-valued surface PDE in a form suitable to be solved by established tools for scalar-valued surface PDEs. We consider piecewise linear Lagrange surface finite elements on triangulated surfaces and validate the approach by a vector- and a tensor-valued surface Helmholtz problem on an ellipsoid. We experimentally show optimal (linear) order of convergence for these problems. The full functionality is demonstrated by solving a surface Landau-de Gennes problem on the Stanford bunny. All tools required to apply this approach to other vector- and tensor-valued surface PDEs are provided. © 2019 Elsevier Inc.},
      author_keywords={Finite element method; Liquid crystals; Surface PDEs; Tensor fields},
      document_type={Article},
      source={Scopus},
      }

  • Exploring the write-in process in molecular quantum cellular automata: A combined modelingand first-principle approach
    • A. Santana-Bonilla, L. Medrano Sandonas, R. Gutierrez, G. Cuniberti
    • Journal of Physics Condensed Matter 31, 405502 (2019)
    • DOI   Abstract  

      The molecular quantum cellular automata paradigm (m-QCA) offers a promising alternative framework to current CMOS implementations. A crucial aspect for implementing this technology concerns the construction of a device which effectively controls intramolecular charge-transfer processes. Tentative experimental implementations have been developed in which a voltage drop is created generating the forces that drive a molecule into a logic state. However, important factors such as the electric field profile, its possible time-dependency and the influence of temperature in the overall success of charge-transfer are relevant issues to be considered in the design of a reliable device. In this work, we theoretically study the role played by these processes in the overall intramolecular charge-transfer process. We have used a Landau-Zener (LZ) model, where different time-dependent electric field profiles have been simulated. The results have been further corroborated employing density functional tight-binding method. The role played by the nuclear motions in the electron-transfer process has been investigated beyond the Born-Oppenheimer approximation by computing the effect of the external electric field in the behavior of the potential energy surface. Hence, we demonstrate that the intramolecular charge-transfer process is a direct consequence of the coherent LZ nonadiabatic tunneling and the hybridization of the diabatic vibronic states which effectively reduces the trapping of the itinerant electron at the donor group. © 2019 IOP Publishing Ltd.

      @ARTICLE{Santana-Bonilla2019,
      author={Santana-Bonilla, A. and Medrano Sandonas, L. and Gutierrez, R. and Cuniberti, G.},
      title={Exploring the write-in process in molecular quantum cellular automata: A combined modelingand first-principle approach},
      journal={Journal of Physics Condensed Matter},
      year={2019},
      volume={31},
      number={40},
      doi={10.1088/1361-648X/ab29c1},
      art_number={405502},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071067573&doi=10.1088%2f1361-648X%2fab29c1&partnerID=40&md5=d9f6650c418b2422ac59cd1b02bd20be},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden University of Technology, Dresden, 01062, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany; Center for Advancing Electronics Dresden, Dresden University of Technology, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, Dresden University of Technology, Dresden, 01062, Germany},
      abstract={The molecular quantum cellular automata paradigm (m-QCA) offers a promising alternative framework to current CMOS implementations. A crucial aspect for implementing this technology concerns the construction of a device which effectively controls intramolecular charge-transfer processes. Tentative experimental implementations have been developed in which a voltage drop is created generating the forces that drive a molecule into a logic state. However, important factors such as the electric field profile, its possible time-dependency and the influence of temperature in the overall success of charge-transfer are relevant issues to be considered in the design of a reliable device. In this work, we theoretically study the role played by these processes in the overall intramolecular charge-transfer process. We have used a Landau-Zener (LZ) model, where different time-dependent electric field profiles have been simulated. The results have been further corroborated employing density functional tight-binding method. The role played by the nuclear motions in the electron-transfer process has been investigated beyond the Born-Oppenheimer approximation by computing the effect of the external electric field in the behavior of the potential energy surface. Hence, we demonstrate that the intramolecular charge-transfer process is a direct consequence of the coherent LZ nonadiabatic tunneling and the hybridization of the diabatic vibronic states which effectively reduces the trapping of the itinerant electron at the donor group. © 2019 IOP Publishing Ltd.},
      author_keywords={charge transfer; density functional tight binding (DFTB); non-adiabatic coupling; quantum cellular automata},
      document_type={Article},
      source={Scopus},
      }

  • Competition Between Kinetics and Thermodynamics During the Growth of Faceted Crystal by Phase Field Modeling
    • M. Albani, R. Bergamaschini, M. Salvalaglio, A. Voigt, L. Miglio, F. Montalenti
    • Physica Status Solidi (B) Basic Research 256, 1800518 (2019)
    • DOI   Abstract  

      The faceting of a growing crystal is theoretically investigated by a continuum model including the incorporation kinetics of adatoms. This allows us for predictions beyond a simple Wulff analysis which typically refers to faceted morphologies in terms of the equilibrium crystal shape for crystals with an anisotropic surface-energy, or to steady-state kinetic shape when the crystals grow with orientation-dependent velocities. A phase-field approach is implemented in order to account simultaneously for these contributions in two- and three dimensions reproducing realistic kinetic pathways for the morphological evolution of crystal surfaces during growth. After a systematic characterization of the faceting determined by orientation-dependent incorporation times, several different crystal morphologies are found by tuning the relative weights of thermodynamic and kinetic driving forces. Applications to realistic systems are finally reported showing the versatility of the proposed approach and demonstrating the key role played by the incorporation dynamics in out-of-equilibrium growth processes. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

      @ARTICLE{Albani2019,
      author={Albani, M. and Bergamaschini, R. and Salvalaglio, M. and Voigt, A. and Miglio, L. and Montalenti, F.},
      title={Competition Between Kinetics and Thermodynamics During the Growth of Faceted Crystal by Phase Field Modeling},
      journal={Physica Status Solidi (B) Basic Research},
      year={2019},
      volume={256},
      number={7},
      doi={10.1002/pssb.201800518},
      art_number={1800518},
      note={cited By 9},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059855966&doi=10.1002%2fpssb.201800518&partnerID=40&md5=1e9da1e13e0c4adcc62d9f817d0e2dd9},
      affiliation={L-NESS and Department of Materials Science, Università di Milano − Bicocca, Milano, 20125, Italy; Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={The faceting of a growing crystal is theoretically investigated by a continuum model including the incorporation kinetics of adatoms. This allows us for predictions beyond a simple Wulff analysis which typically refers to faceted morphologies in terms of the equilibrium crystal shape for crystals with an anisotropic surface-energy, or to steady-state kinetic shape when the crystals grow with orientation-dependent velocities. A phase-field approach is implemented in order to account simultaneously for these contributions in two- and three dimensions reproducing realistic kinetic pathways for the morphological evolution of crystal surfaces during growth. After a systematic characterization of the faceting determined by orientation-dependent incorporation times, several different crystal morphologies are found by tuning the relative weights of thermodynamic and kinetic driving forces. Applications to realistic systems are finally reported showing the versatility of the proposed approach and demonstrating the key role played by the incorporation dynamics in out-of-equilibrium growth processes. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim},
      author_keywords={crystal faceting; incorporation time; kinetics; phase-field; surface diffusion},
      document_type={Article},
      source={Scopus},
      }

  • Electron transport through NiSi2-Si contacts and their role in reconfigurable field-effect transistors
    • F. Fuchs, S. Gemming, J. Schuster
    • Journal of Physics Condensed Matter 31, 355002 (2019)
    • DOI   Abstract  

      A model is presented which describes reconfigurable field-effect transistors (RFETs) with metal contacts, whose switching is controlled by manipulating the Schottky barriers at the contacts. The proposed modeling approach is able to bridge the gap between quantum effects on the atomic scale and the transistor switching. We apply the model to transistors with a silicon channel and NiSi2 contacts. All relevant crystal orientations are compared, focusing on the differences between electron and hole current, which can be as large as four orders of magnitude. Best symmetry is found for the orientation, which makes this orientation most advantageous for RFETs. The observed differences are analyzed in terms of the Schottky barrier height at the interface. Our study indicates that the precise orientation of the interface relative to a given transport direction, perpendicular or tilted, is an important technology parameter, which has been underestimated during the previous development of RFETs. Most of the conclusions regarding the studied metal-semiconductor interface are also valid for other device architectures. © 2019 IOP Publishing Ltd.

      @ARTICLE{Fuchs2019,
      author={Fuchs, F. and Gemming, S. and Schuster, J.},
      title={Electron transport through NiSi2-Si contacts and their role in reconfigurable field-effect transistors},
      journal={Journal of Physics Condensed Matter},
      year={2019},
      volume={31},
      number={35},
      doi={10.1088/1361-648X/ab2310},
      art_number={355002},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85069889762&doi=10.1088%2f1361-648X%2fab2310&partnerID=40&md5=9cc716b6f4696fa39c91ab909e44a4ce},
      affiliation={Institute of Physics, Chemnitz University of Technology, Chemnitz, Germany; Center for Advancing Electronics Dresden, Dresden, Germany; Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Dresden, Germany; Fraunhofer Institute for Electronic Nano Systems, Chemnitz, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, Germany; Center for Microtechnologies, Chemnitz University of Technology, Chemnitz, Germany},
      abstract={A model is presented which describes reconfigurable field-effect transistors (RFETs) with metal contacts, whose switching is controlled by manipulating the Schottky barriers at the contacts. The proposed modeling approach is able to bridge the gap between quantum effects on the atomic scale and the transistor switching. We apply the model to transistors with a silicon channel and NiSi2 contacts. All relevant crystal orientations are compared, focusing on the differences between electron and hole current, which can be as large as four orders of magnitude. Best symmetry is found for the orientation, which makes this orientation most advantageous for RFETs. The observed differences are analyzed in terms of the Schottky barrier height at the interface. Our study indicates that the precise orientation of the interface relative to a given transport direction, perpendicular or tilted, is an important technology parameter, which has been underestimated during the previous development of RFETs. Most of the conclusions regarding the studied metal-semiconductor interface are also valid for other device architectures. © 2019 IOP Publishing Ltd.},
      author_keywords={density functional theory; electron transport; metal-semiconductor interface; nickel silicide; Schottky barrier; silicon},
      document_type={Article},
      source={Scopus},
      }

  • Combined molecular dynamics and phase-field modelling of crack propagation in defective graphene
    • A. C. Hansen-Dörr, L. Wilkens, A. Croy, A. Dianat, G. Cuniberti, M. Kästner
    • Computational Materials Science 163, 117-126 (2019)
    • DOI   Abstract  

      In this work, a combined modelling approach for crack propagation in defective graphene is presented. Molecular dynamics (MD) simulations are used to obtain material parameters (YOUNG’s modulus and Poisson ratio) and to determine the energy contributions during the crack evolution. The elastic properties are then applied in phase-field continuum simulations which are based on the Griffith energy criterion for fracture. In particular, the influence of point defects on elastic properties and the fracture toughness are investigated. For the latter, we obtain values consistent with recent experimental findings. Further, we discuss alternative definitions of an effective fracture toughness, which accounts for the conditions of crack propagation and establishes a link between dynamic, discrete and continuous, quasi-static fracture processes on MD level and continuum level, respectively. It is demonstrated that the combination of MD and phase-field simulations is a well-founded approach to identify defect-dependent material parameters. © 2019

      @ARTICLE{Hansen-Dörr2019117,
      author={Hansen-Dörr, A.C. and Wilkens, L. and Croy, A. and Dianat, A. and Cuniberti, G. and Kästner, M.},
      title={Combined molecular dynamics and phase-field modelling of crack propagation in defective graphene},
      journal={Computational Materials Science},
      year={2019},
      volume={163},
      pages={117-126},
      doi={10.1016/j.commatsci.2019.03.028},
      note={cited By 10},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063272269&doi=10.1016%2fj.commatsci.2019.03.028&partnerID=40&md5=0fb6c712efa599642b3e4c8111dbc41a},
      affiliation={Institute of Solid Mechanics, TU Dresden, Dresden, Germany; Institute of Materials Science, TU Dresden, Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, Germany},
      abstract={In this work, a combined modelling approach for crack propagation in defective graphene is presented. Molecular dynamics (MD) simulations are used to obtain material parameters (YOUNG's modulus and Poisson ratio) and to determine the energy contributions during the crack evolution. The elastic properties are then applied in phase-field continuum simulations which are based on the Griffith energy criterion for fracture. In particular, the influence of point defects on elastic properties and the fracture toughness are investigated. For the latter, we obtain values consistent with recent experimental findings. Further, we discuss alternative definitions of an effective fracture toughness, which accounts for the conditions of crack propagation and establishes a link between dynamic, discrete and continuous, quasi-static fracture processes on MD level and continuum level, respectively. It is demonstrated that the combination of MD and phase-field simulations is a well-founded approach to identify defect-dependent material parameters. © 2019},
      author_keywords={Combined approach; Fracture of defective graphene; Molecular dynamics; Phase-field modelling},
      document_type={Article},
      source={Scopus},
      }

  • Influence of lattice termination on the edge states of the quantum spin Hall insulator monolayer 1T′-WTe2
    • A. Lau, R. Ray, D. Varjas, A. R. Akhmerov
    • Physical Review Materials 3, 054206 (2019)
    • DOI   Abstract  

      We study the influence of sample termination on the electronic properties of the novel quantum spin Hall insulator monolayer 1T′-WTe2. For this purpose, we construct an accurate, minimal four-orbital tight-binding model with spin-orbit coupling by employing a combination of density-functional theory calculations, symmetry considerations, and fitting to experimental data. Based on this model, we compute energy bands and two-terminal conductance spectra for various ribbon geometries with different terminations, with and without a magnetic field. Because of the strong electron-hole asymmetry, we find that the edge Dirac point is buried in the bulk bands for most edge terminations. In the presence of a magnetic field, an in-gap edge Dirac point leads to exponential suppression of conductance as an edge Zeeman gap opens, whereas the conductance stays at the quantized value when the Dirac point is buried in the bulk bands. Finally, we find that disorder in the edge termination drastically changes this picture: the conductance of a sufficiently rough edge is uniformly suppressed for all energies in the bulk gap regardless of the orientation of the edge. © 2019 American Physical Society.

      @ARTICLE{Lau2019,
      author={Lau, A. and Ray, R. and Varjas, D. and Akhmerov, A.R.},
      title={Influence of lattice termination on the edge states of the quantum spin Hall insulator monolayer 1T′-WTe2},
      journal={Physical Review Materials},
      year={2019},
      volume={3},
      number={5},
      doi={10.1103/PhysRevMaterials.3.054206},
      art_number={054206},
      note={cited By 6},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066789765&doi=10.1103%2fPhysRevMaterials.3.054206&partnerID=40&md5=76433cb5e38ac2ec4b34f358a5fd9c9a},
      affiliation={Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 4056, Delft, 2600 GA, Netherlands; Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; QuTech, Delft University of Technology, P.O. Box 4056, Delft, 2600 GA, Netherlands},
      abstract={We study the influence of sample termination on the electronic properties of the novel quantum spin Hall insulator monolayer 1T′-WTe2. For this purpose, we construct an accurate, minimal four-orbital tight-binding model with spin-orbit coupling by employing a combination of density-functional theory calculations, symmetry considerations, and fitting to experimental data. Based on this model, we compute energy bands and two-terminal conductance spectra for various ribbon geometries with different terminations, with and without a magnetic field. Because of the strong electron-hole asymmetry, we find that the edge Dirac point is buried in the bulk bands for most edge terminations. In the presence of a magnetic field, an in-gap edge Dirac point leads to exponential suppression of conductance as an edge Zeeman gap opens, whereas the conductance stays at the quantized value when the Dirac point is buried in the bulk bands. Finally, we find that disorder in the edge termination drastically changes this picture: the conductance of a sufficiently rough edge is uniformly suppressed for all energies in the bulk gap regardless of the orientation of the edge. © 2019 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Photocatalytic microporous membrane against the increasing problem of water emerging pollutants
    • P. M. Martins, J. M. Ribeiro, S. Teixeira, D. Y. Petrovykh, G. Cuniberti, L. Pereira, S. Lanceros-Méndez
    • Materials 12, 1649 (2019)
    • DOI   Abstract  

      Emerging pollutants are an essential class of recalcitrant contaminants that are not eliminated from water after conventional treatment. Here, a photocatalytic microporous membrane based on polyvinylidene difluoride-co-trifluoroethylene (PVDF-TrFE) with immobilised TiO2 nanoparticles, prepared by solvent casting, was tested against representative emerging pollutants. The structure and composition of these polymeric membranes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, porosimetry, and contact angle goniometry. The nanocomposites exhibited a porous structure with a uniform distribution of TiO2 nanoparticles. The addition of TiO2 did not change the structure of the polymeric matrix; however, it increased the wettability of the nanocomposite. The nanocomposites degraded 99% of methylene blue (MB), 95% of ciprofloxacin (CIP), and 48% of ibuprofen (IBP). The microporous nanocomposite exhibited no photocatalytic efficiency loss after four use cycles, corresponding to 20 h of UV irradiation. The reusability of this system confirms the promising nature of polymer nanocomposites as the basis for cost-effective and scalable treatments of emerging pollutants. © 2019 by the authors.

      @ARTICLE{Martins2019,
      author={Martins, P.M. and Ribeiro, J.M. and Teixeira, S. and Petrovykh, D.Y. and Cuniberti, G. and Pereira, L. and Lanceros-Méndez, S.},
      title={Photocatalytic microporous membrane against the increasing problem of water emerging pollutants},
      journal={Materials},
      year={2019},
      volume={12},
      number={10},
      doi={10.3390/ma12101649},
      art_number={1649},
      note={cited By 6},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066834498&doi=10.3390%2fma12101649&partnerID=40&md5=9f5654c0e0a013b72fc16133cf5984f6},
      affiliation={Centre of Physics, University of Minho, Braga, 4710-057, Portugal; Department of Biological Engineering, University of Minho, Braga, 4710-057, Portugal; Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, Braga, 4710-057, Portugal; Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga, Braga, 4715-330, Portugal; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Basque Center for Materials, Applications and Nanostructures, UPV/EHU Science Park, Leioa, 48940, Spain; IKERBASQUE, Basque Foundation for Science, Bilbao, 48013, Spain},
      abstract={Emerging pollutants are an essential class of recalcitrant contaminants that are not eliminated from water after conventional treatment. Here, a photocatalytic microporous membrane based on polyvinylidene difluoride-co-trifluoroethylene (PVDF-TrFE) with immobilised TiO2 nanoparticles, prepared by solvent casting, was tested against representative emerging pollutants. The structure and composition of these polymeric membranes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, porosimetry, and contact angle goniometry. The nanocomposites exhibited a porous structure with a uniform distribution of TiO2 nanoparticles. The addition of TiO2 did not change the structure of the polymeric matrix; however, it increased the wettability of the nanocomposite. The nanocomposites degraded 99% of methylene blue (MB), 95% of ciprofloxacin (CIP), and 48% of ibuprofen (IBP). The microporous nanocomposite exhibited no photocatalytic efficiency loss after four use cycles, corresponding to 20 h of UV irradiation. The reusability of this system confirms the promising nature of polymer nanocomposites as the basis for cost-effective and scalable treatments of emerging pollutants. © 2019 by the authors.},
      author_keywords={Immobilization; Pharmaceuticals; Photocatalysis; PVDF-TrFE; Titanium dioxide},
      document_type={Article},
      source={Scopus},
      }

  • Topological and geometrical quantities in active cellular structures
    • D. Wenzel, S. Praetorius, A. Voigt
    • Journal of Chemical Physics 150, 164108 (2019)
    • DOI   Abstract  

      Topological and geometrical properties and the associated topological defects find a rapidly growing interest in studying the interplay between mechanics and the collective behavior of cells on the tissue level. We here test if well studied equilibrium laws for polydisperse passive systems such as Lewis‘ and Aboav-Weaire’s law are applicable also for active cellular structures. Large scale simulations, which are based on a multiphase field active polar gel model, indicate that these active cellular structures follow these laws. If the system is in a state of collective motion, quantitative agreement with typical values for passive systems is also observed. If this state has not developed, quantitative differences can be found. We further compare the model with discrete modeling approaches for cellular structures and show that essential properties, such as T1 transitions and rosettes, are naturally fulfilled. © 2019 Author(s).

      @ARTICLE{Wenzel2019,
      author={Wenzel, D. and Praetorius, S. and Voigt, A.},
      title={Topological and geometrical quantities in active cellular structures},
      journal={Journal of Chemical Physics},
      year={2019},
      volume={150},
      number={16},
      doi={10.1063/1.5085766},
      art_number={164108},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064910704&doi=10.1063%2f1.5085766&partnerID=40&md5=e66750f70a9b486a9303e8663a89538e},
      affiliation={Institute of Scientific Computing, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Systems Biology Dresden (CSBD), Pfotenhauerstr. 108, Dresden, 01307, Germany},
      abstract={Topological and geometrical properties and the associated topological defects find a rapidly growing interest in studying the interplay between mechanics and the collective behavior of cells on the tissue level. We here test if well studied equilibrium laws for polydisperse passive systems such as Lewis' and Aboav-Weaire's law are applicable also for active cellular structures. Large scale simulations, which are based on a multiphase field active polar gel model, indicate that these active cellular structures follow these laws. If the system is in a state of collective motion, quantitative agreement with typical values for passive systems is also observed. If this state has not developed, quantitative differences can be found. We further compare the model with discrete modeling approaches for cellular structures and show that essential properties, such as T1 transitions and rosettes, are naturally fulfilled. © 2019 Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Impact of device geometry on electron and phonon transport in graphene nanorings
    • M. Saiz-Bretín, L. Medrano Sandonas, R. Gutierrez, G. Cuniberti, F. Domínguez-Adame
    • Physical Review B 99, 165428 (2019)
    • DOI   Abstract  

      Recent progress in nanostructuring of materials opens up possibilities to achieve more efficient thermoelectric devices. Nanofilms, nanowires, and nanorings may show increased phonon scattering while keeping good electron transport, two of the basic ingredients for designing more efficient thermoelectric systems. Here we argue that graphene nanorings attached to two leads meet these two requirements. Using a density-functional parametrized tight-binding method combined with Green’s function technique, we show that the lattice thermal conductance is largely reduced as compared to that of graphene nanoribbons. At the same time, numerical calculations based on the quantum transmission boundary method, combined with an effective transfer matrix method, predict that the electric properties are not considerably deteriorated, leading to an overall remarkable thermoelectric efficiency. We conclude that graphene nanorings can be regarded as promising candidates for nanoscale thermoelectric devices. © 2019 American Physical Society.

      @ARTICLE{Saiz-Bretín2019,
      author={Saiz-Bretín, M. and Medrano Sandonas, L. and Gutierrez, R. and Cuniberti, G. and Domínguez-Adame, F.},
      title={Impact of device geometry on electron and phonon transport in graphene nanorings},
      journal={Physical Review B},
      year={2019},
      volume={99},
      number={16},
      doi={10.1103/PhysRevB.99.165428},
      art_number={165428},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065238895&doi=10.1103%2fPhysRevB.99.165428&partnerID=40&md5=c3cdf07ce468a27d42f7fcc761b144d0},
      affiliation={GISC, Departamento de Física de Materiales, Universidad Complutense, Madrid, E-28040, Spain; Institute for Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany},
      abstract={Recent progress in nanostructuring of materials opens up possibilities to achieve more efficient thermoelectric devices. Nanofilms, nanowires, and nanorings may show increased phonon scattering while keeping good electron transport, two of the basic ingredients for designing more efficient thermoelectric systems. Here we argue that graphene nanorings attached to two leads meet these two requirements. Using a density-functional parametrized tight-binding method combined with Green's function technique, we show that the lattice thermal conductance is largely reduced as compared to that of graphene nanoribbons. At the same time, numerical calculations based on the quantum transmission boundary method, combined with an effective transfer matrix method, predict that the electric properties are not considerably deteriorated, leading to an overall remarkable thermoelectric efficiency. We conclude that graphene nanorings can be regarded as promising candidates for nanoscale thermoelectric devices. © 2019 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Green function, quasi-classical Langevin and Kubo-Greenwood methods in quantum thermal transport
    • H. Sevinçli, S. Roche, G. Cuniberti, M. Brandbyge, R. Gutierrez, L. M. Sandonas
    • Journal of Physics Condensed Matter 31, 273003 (2019)
    • DOI   Abstract  

      With the advances in fabrication of materials with feature sizes at the order of nanometers, it has been possible to alter their thermal transport properties dramatically. Miniaturization of device size increases the power density in general, hence faster electronics require better thermal transport, whereas better thermoelectric applications require the opposite. Such diverse needs bring new challenges for material design. Shrinkage of length scales has also changed the experimental and theoretical methods to study thermal transport. Unsurprisingly, novel approaches have emerged to control phonon flow. Besides, ever increasing computational power is another driving force for developing new computational methods. In this review, we discuss three methods developed for computing vibrational thermal transport properties of nano-structured systems, namely Green function, quasi-classical Langevin, and Kubo-Green methods. The Green function methods are explained using both nonequilibrium expressions and the Landauer-type formula. The partitioning scheme, decimation techniques and surface Green functions are reviewed, and a simple model for reservoir Green functions is shown. The expressions for the Kubo-Greenwood method are derived, and Lanczos tridiagonalization, continued fraction and Chebyshev polynomial expansion methods are discussed. Additionally, the quasi-classical Langevin approach, which is useful for incorporating phonon-phonon and other scatterings is summarized. © 2019 IOP Publishing Ltd.

      @ARTICLE{Sevinçli2019,
      author={Sevinçli, H. and Roche, S. and Cuniberti, G. and Brandbyge, M. and Gutierrez, R. and Sandonas, L.M.},
      title={Green function, quasi-classical Langevin and Kubo-Greenwood methods in quantum thermal transport},
      journal={Journal of Physics Condensed Matter},
      year={2019},
      volume={31},
      number={27},
      doi={10.1088/1361-648X/ab119a},
      art_number={273003},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065809227&doi=10.1088%2f1361-648X%2fab119a&partnerID=40&md5=7a3e495715e59d22fc7882bd2e606669},
      affiliation={Department of Materials Science and Engineering, Izmir Institute of Technology, Urla, Izmir, 35430, Turkey; Catalan Institute of Nanoscience and Nanotechnology (ICN2), Campus UAB, CSIC and BIST, Barcelona,Bellaterra, 08193, Spain; ICREA, Instituci o Catalana de Recerca i Estudis Avancats, Barcelona, 08070, Spain; Institute for Materials Science and Max Bergmann Center of Biomaterials, Dresden, 01062, Germany; Dresden Center for Computational Materials Science and Center for Advancing Electronics Dresden, Dresden, 01062, Germany; Department of Micro-And Nanotechnology (DTU Nanotech), Center for Nanostructured Graphene (CNG), Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark; Max Planck Institute for Physics of Complex Systems, Dresden, 01187, Germany},
      abstract={With the advances in fabrication of materials with feature sizes at the order of nanometers, it has been possible to alter their thermal transport properties dramatically. Miniaturization of device size increases the power density in general, hence faster electronics require better thermal transport, whereas better thermoelectric applications require the opposite. Such diverse needs bring new challenges for material design. Shrinkage of length scales has also changed the experimental and theoretical methods to study thermal transport. Unsurprisingly, novel approaches have emerged to control phonon flow. Besides, ever increasing computational power is another driving force for developing new computational methods. In this review, we discuss three methods developed for computing vibrational thermal transport properties of nano-structured systems, namely Green function, quasi-classical Langevin, and Kubo-Green methods. The Green function methods are explained using both nonequilibrium expressions and the Landauer-type formula. The partitioning scheme, decimation techniques and surface Green functions are reviewed, and a simple model for reservoir Green functions is shown. The expressions for the Kubo-Greenwood method are derived, and Lanczos tridiagonalization, continued fraction and Chebyshev polynomial expansion methods are discussed. Additionally, the quasi-classical Langevin approach, which is useful for incorporating phonon-phonon and other scatterings is summarized. © 2019 IOP Publishing Ltd.},
      author_keywords={Green function method; Kubo-greenwood method; Quantum thermal transport; Quasi-classical langevin method},
      document_type={Review},
      source={Scopus},
      }

  • An efficient numerical framework for the amplitude expansion of the phase-field crystal model
    • S. Praetorius, M. Salvalaglio, A. Voigt
    • Modelling and Simulation in Materials Science and Engineering 27, 044004 (2019)
    • DOI   Abstract  

      The study of polycrystalline materials requires theoretical and computational techniques enabling multiscale investigations. The amplitude expansion of the phase-field crystal model allows for describing crystal lattice properties on diffusive timescales by focusing on continuous fields varying on length scales larger than the atomic spacing. Thus, it allows for the simulation of large systems still retaining details of the crystal lattice. Fostered by the applications of this approach, we present here an efficient numerical framework to solve its equations. In particular, we consider a real space approach exploiting the finite element method. An optimized preconditioner is developed in order to improve the convergence of the linear solver. Moreover, a mesh adaptivity criterion based on the local rotation of the polycrystal is used. This results in an unprecedented capability of simulating large, three-dimensional systems including the dynamical description of the microstructures in polycrystalline materials together with their dislocation networks. © 2019 IOP Publishing Ltd.

      @ARTICLE{Praetorius2019,
      author={Praetorius, S. and Salvalaglio, M. and Voigt, A.},
      title={An efficient numerical framework for the amplitude expansion of the phase-field crystal model},
      journal={Modelling and Simulation in Materials Science and Engineering},
      year={2019},
      volume={27},
      number={4},
      doi={10.1088/1361-651X/ab1508},
      art_number={044004},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064274891&doi=10.1088%2f1361-651X%2fab1508&partnerID=40&md5=8937dd6824447312ea5d07c95a356ae9},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, D-01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, D-01062, Germany},
      abstract={The study of polycrystalline materials requires theoretical and computational techniques enabling multiscale investigations. The amplitude expansion of the phase-field crystal model allows for describing crystal lattice properties on diffusive timescales by focusing on continuous fields varying on length scales larger than the atomic spacing. Thus, it allows for the simulation of large systems still retaining details of the crystal lattice. Fostered by the applications of this approach, we present here an efficient numerical framework to solve its equations. In particular, we consider a real space approach exploiting the finite element method. An optimized preconditioner is developed in order to improve the convergence of the linear solver. Moreover, a mesh adaptivity criterion based on the local rotation of the polycrystal is used. This results in an unprecedented capability of simulating large, three-dimensional systems including the dynamical description of the microstructures in polycrystalline materials together with their dislocation networks. © 2019 IOP Publishing Ltd.},
      author_keywords={coarse graining; dislocations; finite element method; grain boundaries; phase field crystal; phase field modeling; polycrystalline growth},
      document_type={Article},
      source={Scopus},
      }

  • Selective Transmission of Phonons in Molecular Junctions with Nanoscopic Thermal Baths
    • L. Medrano Sandonas, A. Rodríguez Méndez, R. Gutierrez, J. M. Ugalde, V. Mujica, G. Cuniberti
    • Journal of Physical Chemistry C 123, 9680-9687 (2019)
    • DOI   Abstract  

      A fundamental problem for thermal energy harvesting is the development of atomistic design strategies for smart nanodevices and nanomaterials that can be used to selectively transmit heat. We carry out here an extensive computational study demonstrating that heterogeneous molecular junctions, consisting of molecular wires bridging two different nanocontacts, can act as a selective phonon filter. The most important finding is the appearance of gaps on the phonon transmittance spectrum, which are strongly correlated to the properties of the vibrational spectrum of the specific molecular species in the junction. The filtering effect results from a delicate interplay between the intrinsic vibrational structure of the molecular chains and the different Debye cutoffs of the nanoscopic electrodes used as thermal baths. Copyright © 2019 American Chemical Society.

      @ARTICLE{MedranoSandonas20199680,
      author={Medrano Sandonas, L. and Rodríguez Méndez, A. and Gutierrez, R. and Ugalde, J.M. and Mujica, V. and Cuniberti, G.},
      title={Selective Transmission of Phonons in Molecular Junctions with Nanoscopic Thermal Baths},
      journal={Journal of Physical Chemistry C},
      year={2019},
      volume={123},
      number={15},
      pages={9680-9687},
      doi={10.1021/acs.jpcc.8b11879},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064338979&doi=10.1021%2facs.jpcc.8b11879&partnerID=40&md5=30bde626e92df12c89fa1da90359a33d},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Kimika Fakultatea, Euskal Herriko Unibertsitatea (UPV/EHU), P.K. 1072, Euskadi, Donostia, 20080, Spain; Donostia International Physics Center (DIPC), P.K. 1072, Euskadi, Donostia, 20080, Spain; School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, United States; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={A fundamental problem for thermal energy harvesting is the development of atomistic design strategies for smart nanodevices and nanomaterials that can be used to selectively transmit heat. We carry out here an extensive computational study demonstrating that heterogeneous molecular junctions, consisting of molecular wires bridging two different nanocontacts, can act as a selective phonon filter. The most important finding is the appearance of gaps on the phonon transmittance spectrum, which are strongly correlated to the properties of the vibrational spectrum of the specific molecular species in the junction. The filtering effect results from a delicate interplay between the intrinsic vibrational structure of the molecular chains and the different Debye cutoffs of the nanoscopic electrodes used as thermal baths. Copyright © 2019 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Electron Transport through Self-Assembled Monolayers of Tripeptides
    • E. Mervinetsky, I. Alshanski, S. Lenfant, D. Guerin, L. Medrano Sandonas, A. Dianat, R. Gutierrez, G. Cuniberti, M. Hurevich, S. Yitzchaik, D. Vuillaume
    • Journal of Physical Chemistry C 123, 9600-9608 (2019)
    • DOI   Abstract  

      We report how the electron transport through a solid-state metal/Gly-Gly-His (GGH) tripeptide monolayer/metal junction and the metal/GGH work function (WF) are modified by the GGH complexation with Cu2+ ions. Conducting atomic force microscopy is used to measure the current-voltage histograms. The WF is characterized by combining macroscopic Kelvin probe and Kelvin probe force microscopy at the nanoscale. We observe that the complexation of Cu2+ ions with the GGH monolayer is highly dependent on the molecular surface density and results in opposite trends. In the case of a high-density monolayer the conformational changes are hindered by the proximity of the neighboring peptides, hence forming an insulating layer in response to copper complexation. However, the monolayers of a slightly lower density allow for the conformational change to a looped peptide wrapping the Cu-ion, which results in a more conductive monolayer. Copper-ion complexation to the high- and low-density monolayers systematically induces an increase of the WFs. Copper-ion complexation to the low-density monolayer induces an increase of electron-transport efficiency, whereas the copper-ion complexation to the high-density monolayer results in a slight decrease of electron transport. Both of the observed trends agree with first-principle calculations. Complexation of copper to the low-density GGH monolayer induces a new gap state slightly above the Au Fermi energy that is absent in the high-density monolayer. © Copyright © 2019 American Chemical Society.

      @ARTICLE{Mervinetsky20199600,
      author={Mervinetsky, E. and Alshanski, I. and Lenfant, S. and Guerin, D. and Medrano Sandonas, L. and Dianat, A. and Gutierrez, R. and Cuniberti, G. and Hurevich, M. and Yitzchaik, S. and Vuillaume, D.},
      title={Electron Transport through Self-Assembled Monolayers of Tripeptides},
      journal={Journal of Physical Chemistry C},
      year={2019},
      volume={123},
      number={14},
      pages={9600-9608},
      doi={10.1021/acs.jpcc.9b01082},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064275523&doi=10.1021%2facs.jpcc.9b01082&partnerID=40&md5=ea033e76ecce5343d65dd5c268fdad43},
      affiliation={Institute of Chemistry, Hebrew University of Jerusalem, Safra Campus, Givat Ram, Jerusalem, 91904, Israel; Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Safra Campus, Jerusalem, 91904, Israel; Institute for Electronics Microelectronics and Nanotechnology, CNRS, Université de Lille, Villeneuve d'Ascq, 59652, France; Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01069, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={We report how the electron transport through a solid-state metal/Gly-Gly-His (GGH) tripeptide monolayer/metal junction and the metal/GGH work function (WF) are modified by the GGH complexation with Cu2+ ions. Conducting atomic force microscopy is used to measure the current-voltage histograms. The WF is characterized by combining macroscopic Kelvin probe and Kelvin probe force microscopy at the nanoscale. We observe that the complexation of Cu2+ ions with the GGH monolayer is highly dependent on the molecular surface density and results in opposite trends. In the case of a high-density monolayer the conformational changes are hindered by the proximity of the neighboring peptides, hence forming an insulating layer in response to copper complexation. However, the monolayers of a slightly lower density allow for the conformational change to a looped peptide wrapping the Cu-ion, which results in a more conductive monolayer. Copper-ion complexation to the high- and low-density monolayers systematically induces an increase of the WFs. Copper-ion complexation to the low-density monolayer induces an increase of electron-transport efficiency, whereas the copper-ion complexation to the high-density monolayer results in a slight decrease of electron transport. Both of the observed trends agree with first-principle calculations. Complexation of copper to the low-density GGH monolayer induces a new gap state slightly above the Au Fermi energy that is absent in the high-density monolayer. © Copyright © 2019 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Magnetic anisotropy and spin-polarized two-dimensional electron gas in the van der Waals ferromagnet Cr2Ge2Te6
    • J. Zeisner, A. Alfonsov, S. Selter, S. Aswartham, M. P. Ghimire, M. Richter, J. Van Den Brink, B. Büchner, V. Kataev
    • Physical Review B 99, 165109 (2019)
    • DOI   Abstract  

      We report a comprehensive experimental investigation on the magnetic anisotropy in bulk single crystals of Cr2Ge2Te6, a quasi-two-dimensional ferromagnet belonging to the family of magnetic layered transition metal trichalcogenides that have recently attracted a great deal of interest with regard to the fundamental and applied aspects of two-dimensional magnetism. For this purpose electron spin resonance (ESR) and ferromagnetic resonance (FMR) measurements have been carried out over a wide frequency and temperature range. A gradual change in the angular dependence of the ESR linewidth at temperatures above the ferromagnetic transition temperature Tc reveals the development of two-dimensional spin correlations in the vicinity of Tc thereby proving the intrinsically low-dimensional character of spin dynamics in Cr2Ge2Te6. Angular and frequency dependent measurements in the ferromagnetic phase clearly show an easy-axis-type anisotropy of this compound. Furthermore, these experiments are compared with simulations based on a phenomenological approach, which takes into account results of static magnetization measurements as well as high temperature g factors obtained from ESR spectroscopy in the paramagnetic phase. As a result the determined magnetocrystalline anisotropy energy density (MAE) KU is (0.48±0.02)×106 erg/cm3. This analysis is complemented by density functional calculations which yield the experimental MAE value for a particular value of the electronic correlation strength U. The analysis of the electronic structure reveals that the low-lying conduction band carries almost completely spin-polarized, quasihomogeneous, two-dimensional states. © 2019 American Physical Society.

      @ARTICLE{Zeisner2019,
      author={Zeisner, J. and Alfonsov, A. and Selter, S. and Aswartham, S. and Ghimire, M.P. and Richter, M. and Van Den Brink, J. and Büchner, B. and Kataev, V.},
      title={Magnetic anisotropy and spin-polarized two-dimensional electron gas in the van der Waals ferromagnet Cr2Ge2Te6},
      journal={Physical Review B},
      year={2019},
      volume={99},
      number={16},
      doi={10.1103/PhysRevB.99.165109},
      art_number={165109},
      note={cited By 17},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064133163&doi=10.1103%2fPhysRevB.99.165109&partnerID=40&md5=0dd243ad52010b0e4a95b080ae0ab8f1},
      affiliation={Leibniz Institute for Solid State and Materials Research IFW Dresden, Dresden, 01069, Germany; Institute for Solid State and Materials Physics, TU Dresden, Dresden, 01062, Germany; Central Department of Physics, Tribhuvan University, Kirtipur, Kathmandu, 44613, Nepal; Condensed Matter Physics Research Center, Butwal-11, Rupandehi, Lumbini, Nepal; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={We report a comprehensive experimental investigation on the magnetic anisotropy in bulk single crystals of Cr2Ge2Te6, a quasi-two-dimensional ferromagnet belonging to the family of magnetic layered transition metal trichalcogenides that have recently attracted a great deal of interest with regard to the fundamental and applied aspects of two-dimensional magnetism. For this purpose electron spin resonance (ESR) and ferromagnetic resonance (FMR) measurements have been carried out over a wide frequency and temperature range. A gradual change in the angular dependence of the ESR linewidth at temperatures above the ferromagnetic transition temperature Tc reveals the development of two-dimensional spin correlations in the vicinity of Tc thereby proving the intrinsically low-dimensional character of spin dynamics in Cr2Ge2Te6. Angular and frequency dependent measurements in the ferromagnetic phase clearly show an easy-axis-type anisotropy of this compound. Furthermore, these experiments are compared with simulations based on a phenomenological approach, which takes into account results of static magnetization measurements as well as high temperature g factors obtained from ESR spectroscopy in the paramagnetic phase. As a result the determined magnetocrystalline anisotropy energy density (MAE) KU is (0.48±0.02)×106 erg/cm3. This analysis is complemented by density functional calculations which yield the experimental MAE value for a particular value of the electronic correlation strength U. The analysis of the electronic structure reveals that the low-lying conduction band carries almost completely spin-polarized, quasihomogeneous, two-dimensional states. © 2019 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Towards infinite tilings with symmetric boundaries
    • F. Stenger, A. Voigt
    • Symmetry 11, 444 (2019)
    • DOI   Abstract  

      Large-time coarsening and the associated scaling and statistically self-similar properties are used to construct infinite tilings. This is realized using a Cahn-Hilliard equation and special boundaries on each tile. Within a compromise between computational effort and the goal to reduce recurrences, an infinite tiling has been created and software which zooms in and out evolve forward and backward in time as well as traverse the infinite tiling horizontally and vertically. We also analyze the scaling behavior and the statistically self-similar properties and describe the numerical approach, which is based on finite elements and an energy-stable time discretization. © 2019 by the authors.

      @ARTICLE{Stenger2019,
      author={Stenger, F. and Voigt, A.},
      title={Towards infinite tilings with symmetric boundaries},
      journal={Symmetry},
      year={2019},
      volume={11},
      number={4},
      doi={10.3390/sym11040444},
      art_number={444},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065493258&doi=10.3390%2fsym11040444&partnerID=40&md5=6fb671413f33c29c7da454a183855f5c},
      affiliation={Institute of Scientific Computing, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={Large-time coarsening and the associated scaling and statistically self-similar properties are used to construct infinite tilings. This is realized using a Cahn-Hilliard equation and special boundaries on each tile. Within a compromise between computational effort and the goal to reduce recurrences, an infinite tiling has been created and software which zooms in and out evolve forward and backward in time as well as traverse the infinite tiling horizontally and vertically. We also analyze the scaling behavior and the statistically self-similar properties and describe the numerical approach, which is based on finite elements and an energy-stable time discretization. © 2019 by the authors.},
      author_keywords={Computational design; Finite-element method; Pattern formation; Symmetric boundary condition},
      document_type={Article},
      source={Scopus},
      }

  • Phase-field modelling of interface failure in brittle materials
    • A. C. Hansen-Dörr, R. de Borst, P. Hennig, M. Kästner
    • Computer Methods in Applied Mechanics and Engineering 346, 25-42 (2019)
    • DOI   Abstract  

      A phase-field approach is proposed for interface failure between two possibly dissimilar materials. The discrete adhesive interface is regularised over a finite width. Due to the use of a regularised crack model for the bulk material, an interaction between the length scales of the crack and the interface can occur. An analytic one-dimensional analysis has been carried out to quantify this effect and a correction is proposed, which compensates influences due to the regularisation in the bulk material. For multi-dimensional analyses this approach cannot be used straightforwardly, as is shown, and a study has been undertaken to numerically quantify the compensation factor due to the interaction. The aim is to obtain reliable and universally applicable results for crack propagation along interfaces between dissimilar materials, such that they are independent from the regularisation width of the interface. The method has been tested and validated on three benchmark problems. The compensation is particularly relevant for phase-field analyses in heterogeneous materials, where cohesive failure in the constituent materials as well as adhesive failure at interfaces play a role. © 2018 Elsevier B.V.

      @ARTICLE{Hansen-Dörr201925,
      author={Hansen-Dörr, A.C. and de Borst, R. and Hennig, P. and Kästner, M.},
      title={Phase-field modelling of interface failure in brittle materials},
      journal={Computer Methods in Applied Mechanics and Engineering},
      year={2019},
      volume={346},
      pages={25-42},
      doi={10.1016/j.cma.2018.11.020},
      note={cited By 24},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058511064&doi=10.1016%2fj.cma.2018.11.020&partnerID=40&md5=8e8694ffcdd269024efde18ff87823cd},
      affiliation={Institute of Solid Mechanics, TU Dresden, Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, Germany; University of Sheffield, Department of Civil and Structural Engineering, Mappin Street, Sir Frederick Mappin Building, Sheffield, S1 3JD, United Kingdom},
      abstract={A phase-field approach is proposed for interface failure between two possibly dissimilar materials. The discrete adhesive interface is regularised over a finite width. Due to the use of a regularised crack model for the bulk material, an interaction between the length scales of the crack and the interface can occur. An analytic one-dimensional analysis has been carried out to quantify this effect and a correction is proposed, which compensates influences due to the regularisation in the bulk material. For multi-dimensional analyses this approach cannot be used straightforwardly, as is shown, and a study has been undertaken to numerically quantify the compensation factor due to the interaction. The aim is to obtain reliable and universally applicable results for crack propagation along interfaces between dissimilar materials, such that they are independent from the regularisation width of the interface. The method has been tested and validated on three benchmark problems. The compensation is particularly relevant for phase-field analyses in heterogeneous materials, where cohesive failure in the constituent materials as well as adhesive failure at interfaces play a role. © 2018 Elsevier B.V.},
      author_keywords={Adhesive interface; Brittle fracture; Diffuse interface model; Interface failure; Phase-field modelling},
      document_type={Article},
      source={Scopus},
      }

  • Hydrodynamic interactions in polar liquid crystals on evolving surfaces
    • I. Nitschke, S. Reuther, A. Voigt
    • Physical Review Fluids 4, 044002 (2019)
    • DOI   Abstract  

      We consider the derivation and numerical solution of the flow of passive and active polar liquid crystals, whose molecular orientation is subjected to a tangential anchoring on an evolving curved surface. The underlying passive model is a simplified surface Ericksen-Leslie model, which is derived as a thin-film limit of the corresponding three-dimensional equations with appropriate boundary conditions. A finite element discretization is considered and the effect of hydrodynamics on the interplay of topology, geometric properties, and defect dynamics is studied for this model on various stationary and evolving surfaces. Additionally, we consider an active model. We propose a surface formulation for an active polar viscous gel and exemplarily demonstrate the effect of the underlying curvature on the location of topological defects on a torus. © 2019 American Physical Society..

      @ARTICLE{Nitschke2019,
      author={Nitschke, I. and Reuther, S. and Voigt, A.},
      title={Hydrodynamic interactions in polar liquid crystals on evolving surfaces},
      journal={Physical Review Fluids},
      year={2019},
      volume={4},
      number={4},
      doi={10.1103/PhysRevFluids.4.044002},
      art_number={044002},
      note={cited By 12},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065031797&doi=10.1103%2fPhysRevFluids.4.044002&partnerID=40&md5=16212f8eb3948fc837615eade901f63a},
      affiliation={Institute of Scientific Computing, Technische Universität, Dresden, Germany; Institute of Scientific Computing, Technische Universität Dresden, Dresden Center for Computational Materials Science (DCMS), Center for Systems Biology Dresden (CSBD), Cluster of Excellence Physics of Life (PoL), Dresden, Germany},
      abstract={We consider the derivation and numerical solution of the flow of passive and active polar liquid crystals, whose molecular orientation is subjected to a tangential anchoring on an evolving curved surface. The underlying passive model is a simplified surface Ericksen-Leslie model, which is derived as a thin-film limit of the corresponding three-dimensional equations with appropriate boundary conditions. A finite element discretization is considered and the effect of hydrodynamics on the interplay of topology, geometric properties, and defect dynamics is studied for this model on various stationary and evolving surfaces. Additionally, we consider an active model. We propose a surface formulation for an active polar viscous gel and exemplarily demonstrate the effect of the underlying curvature on the location of topological defects on a torus. © 2019 American Physical Society..},
      document_type={Article},
      source={Scopus},
      }

  • Radially resolved electronic structure and charge carrier transport in silicon nanowires
    • F. Fuchs, S. Gemming, J. Schuster
    • Physica E: Low-Dimensional Systems and Nanostructures 108, 181-186 (2019)
    • DOI   Abstract  

      The electronic structure of silicon nanowires is studied using density functional theory. A radially resolved density of states is discussed for different nanowire diameters and crystal orientations. This approach allows the investigation of spatially varying electronic properties in the radial direction and extends previous studies, which are usually driven by a one-dimensional band structure analysis. We demonstrate strong differences in the electronic structure between the surface and the center of the nanowire, indicating that the carrier transport will mainly take place in the center. For increasing diameters, the density of states in the center approaches the bulk density of states. We find that bulk properties, such as the indirect nature of the band gap, become significant at a nanowire diameter of approximately 5 nm and beyond. Finally, the spatial characteristic of the current is visualized in terms of transmission pathways on the atomic scale. Electron transport is found to be more localized in the nanowire center than the hole transport. It also depends on the crystal orientation of the wire. For the growing demand of silicon nanowires, for example in the field of sensors or field-effect transistors, multiple conclusions can be drawn from the present work, which we discuss towards the end of the publication. © 2018 Elsevier B.V.

      @ARTICLE{Fuchs2019181,
      author={Fuchs, F. and Gemming, S. and Schuster, J.},
      title={Radially resolved electronic structure and charge carrier transport in silicon nanowires},
      journal={Physica E: Low-Dimensional Systems and Nanostructures},
      year={2019},
      volume={108},
      pages={181-186},
      doi={10.1016/j.physe.2018.12.002},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059062217&doi=10.1016%2fj.physe.2018.12.002&partnerID=40&md5=e804cb3aaeeb039dbebef68ccf872dcc},
      affiliation={Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Dresden, Germany; Center for Advancing Electronics Dresden, Dresden, Germany; Institute of Physics, Chemnitz University of Technology, Chemnitz, Germany; Fraunhofer Institute for Electronic Nano Systems, Chemnitz, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, Germany},
      abstract={The electronic structure of silicon nanowires is studied using density functional theory. A radially resolved density of states is discussed for different nanowire diameters and crystal orientations. This approach allows the investigation of spatially varying electronic properties in the radial direction and extends previous studies, which are usually driven by a one-dimensional band structure analysis. We demonstrate strong differences in the electronic structure between the surface and the center of the nanowire, indicating that the carrier transport will mainly take place in the center. For increasing diameters, the density of states in the center approaches the bulk density of states. We find that bulk properties, such as the indirect nature of the band gap, become significant at a nanowire diameter of approximately 5 nm and beyond. Finally, the spatial characteristic of the current is visualized in terms of transmission pathways on the atomic scale. Electron transport is found to be more localized in the nanowire center than the hole transport. It also depends on the crystal orientation of the wire. For the growing demand of silicon nanowires, for example in the field of sensors or field-effect transistors, multiple conclusions can be drawn from the present work, which we discuss towards the end of the publication. © 2018 Elsevier B.V.},
      document_type={Article},
      source={Scopus},
      }

  • Thermal bridging of graphene nanosheets via covalent molecular junctions: A non-equilibrium Green’s functions–density functional tight-binding study
    • D. Martinez Gutierrez, A. Di Pierro, A. Pecchia, L. M. Sandonas, R. Gutierrez, M. Bernal, B. Mortazavi, G. Cuniberti, G. Saracco, A. Fina
    • Nano Research 12, 791-799 (2019)
    • DOI   Abstract  

      Despite the uniquely high thermal conductivity of graphene is well known, the exploitation of graphene into thermally conductive nanomaterials and devices is limited by the inefficiency of thermal contacts between the individual nanosheets. A fascinating yet experimentally challenging route to enhance thermal conductance at contacts between graphene nanosheets is through molecular junctions, allowing covalently connecting nanosheets, otherwise interacting only via weak Van der Waals forces. Beside the bare existence of covalent connections, the choice of molecular structures to be used as thermal junctions should be guided by their vibrational properties, in terms of phonon transfer through the molecular junction. In this paper, density functional tight-binding combined with Green’s functions formalism was applied for the calculation of thermal conductance and phonon spectra of several different aliphatic and aromatic molecular junctions between graphene nanosheets. Effects of molecular junction length, conformation, and aromaticity were studied in detail and correlated with phonon tunnelling spectra. The theoretical insight provided by this work can guide future experimental studies to select suitable molecular junctions, in order to enhance the thermal transport by suppressing the interfacial thermal resistances. This is attractive for various systems, including graphene nanopapers and graphene polymer nanocomposites, as well as related devices. In a broader view, the possibility to design molecular junctions to control phonon transport currently appears as an efficient way to produce phononic devices and controlling heat management in nanostructures. [Figure not available: see fulltext.]. © 2019, Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature.

      @ARTICLE{MartinezGutierrez2019791,
      author={Martinez Gutierrez, D. and Di Pierro, A. and Pecchia, A. and Sandonas, L.M. and Gutierrez, R. and Bernal, M. and Mortazavi, B. and Cuniberti, G. and Saracco, G. and Fina, A.},
      title={Thermal bridging of graphene nanosheets via covalent molecular junctions: A non-equilibrium Green’s functions–density functional tight-binding study},
      journal={Nano Research},
      year={2019},
      volume={12},
      number={4},
      pages={791-799},
      doi={10.1007/s12274-019-2290-2},
      note={cited By 18},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062153066&doi=10.1007%2fs12274-019-2290-2&partnerID=40&md5=84cc9f2a6c6dbfbb2018252d079682bd},
      affiliation={Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, Alessandria, 15121, Italy; Consiglio Nazionale delle Ricerche, ISMN, Monterotondo, 00017, Italy; Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Institute of Structural Mechanics, Bauhaus-Universität Weimar, Weimar, D-99423, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany},
      abstract={Despite the uniquely high thermal conductivity of graphene is well known, the exploitation of graphene into thermally conductive nanomaterials and devices is limited by the inefficiency of thermal contacts between the individual nanosheets. A fascinating yet experimentally challenging route to enhance thermal conductance at contacts between graphene nanosheets is through molecular junctions, allowing covalently connecting nanosheets, otherwise interacting only via weak Van der Waals forces. Beside the bare existence of covalent connections, the choice of molecular structures to be used as thermal junctions should be guided by their vibrational properties, in terms of phonon transfer through the molecular junction. In this paper, density functional tight-binding combined with Green’s functions formalism was applied for the calculation of thermal conductance and phonon spectra of several different aliphatic and aromatic molecular junctions between graphene nanosheets. Effects of molecular junction length, conformation, and aromaticity were studied in detail and correlated with phonon tunnelling spectra. The theoretical insight provided by this work can guide future experimental studies to select suitable molecular junctions, in order to enhance the thermal transport by suppressing the interfacial thermal resistances. This is attractive for various systems, including graphene nanopapers and graphene polymer nanocomposites, as well as related devices. In a broader view, the possibility to design molecular junctions to control phonon transport currently appears as an efficient way to produce phononic devices and controlling heat management in nanostructures. [Figure not available: see fulltext.]. © 2019, Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature.},
      author_keywords={density functional tight-binding (DFTB); graphene; Green’s functions; heat transport; molecular junctions; phonon transmission function; thermal conductance},
      document_type={Article},
      source={Scopus},
      }

  • Controlling Grain Boundaries by Magnetic Fields
    • R. Backofen, K. R. Elder, A. Voigt
    • Physical Review Letters 122, 126103 (2019)
    • DOI   Abstract  

      The ability to use external magnetic fields to influence the microstructure in polycrystalline materials has potential applications in microstructural engineering. To explore this potential and to understand the complex interactions between electromagnetic fields and solid-state matter transport we consider a phase-field-crystal model. Together with efficient and scalable numerical algorithms this allows the examination of the role that external magnetic fields play on the evolution of defect structures and grain boundaries, on diffusive timescales. Examples for planar and circular grain boundaries explain the essential atomistic processes and large scale simulations in 2D are used to obtain statistical data on grain growth under the influence of external fields. © 2019 American Physical Society.

      @ARTICLE{Backofen2019,
      author={Backofen, R. and Elder, K.R. and Voigt, A.},
      title={Controlling Grain Boundaries by Magnetic Fields},
      journal={Physical Review Letters},
      year={2019},
      volume={122},
      number={12},
      doi={10.1103/PhysRevLett.122.126103},
      art_number={126103},
      note={cited By 6},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064037815&doi=10.1103%2fPhysRevLett.122.126103&partnerID=40&md5=1734bd67d3dec6c981a3b8a5360e066e},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Department of Physics, Oakland University, Rochester, MI 48309, United States; Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany},
      abstract={The ability to use external magnetic fields to influence the microstructure in polycrystalline materials has potential applications in microstructural engineering. To explore this potential and to understand the complex interactions between electromagnetic fields and solid-state matter transport we consider a phase-field-crystal model. Together with efficient and scalable numerical algorithms this allows the examination of the role that external magnetic fields play on the evolution of defect structures and grain boundaries, on diffusive timescales. Examples for planar and circular grain boundaries explain the essential atomistic processes and large scale simulations in 2D are used to obtain statistical data on grain growth under the influence of external fields. © 2019 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Mapping Conformational Changes in a Self-Assembled Two-Dimensional Molecular Network by Statistical Analysis of Conductance Images
    • B. Naydenov, S. Torsney, A. S. Bonilla, A. Gualandi, L. Mengozzi, P. G. Cozzi, R. Gutierrez, G. Cuniberti, J. J. Boland
    • Physical Review Applied 11, 034070 (2019)
    • DOI   Abstract  

      A self-assembled two-dimensional (2D) film of tetra-phenyl-porphyrin-4-ferrocene molecules on Au(111) is studied by STM for the presence of intra- and intermolecular correlations in the configurations of the four-pendant ferrocenyl moieties. A statistical analysis of STS images exploits the Pearson’s linear correlation coefficient derived from changes in the molecular electron density across lateral positions in the molecular network as a measure of the intra- and intermolecular coupling and/or conjugation between adjacent equivalent molecular components. Density functional theory (DFT) calculation shows that these electron density changes can be assigned to conformational changes of the ferrocenyl units of the molecules. The methodology presented here can be extended to measure correlations in other 2D systems. © 2019 American Physical Society.

      @ARTICLE{Naydenov2019,
      author={Naydenov, B. and Torsney, S. and Bonilla, A.S. and Gualandi, A. and Mengozzi, L. and Cozzi, P.G. and Gutierrez, R. and Cuniberti, G. and Boland, J.J.},
      title={Mapping Conformational Changes in a Self-Assembled Two-Dimensional Molecular Network by Statistical Analysis of Conductance Images},
      journal={Physical Review Applied},
      year={2019},
      volume={11},
      number={3},
      doi={10.1103/PhysRevApplied.11.034070},
      art_number={034070},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064184651&doi=10.1103%2fPhysRevApplied.11.034070&partnerID=40&md5=1b0a636f91ef108325e4e76c34dc230f},
      affiliation={Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), School of Chemistry, Trinity College Dublin, Dublin 2, Ireland; Institute for Materials Sciences, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; ALMA MATER STUDIORUM UNIVERSITÀ di BOLOGNA, Dipartimento di Chimica G. Ciamician, Via Selmi 2, Bologna, 40126, Italy; Dresden Center for Computational Materials Science (DCCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={A self-assembled two-dimensional (2D) film of tetra-phenyl-porphyrin-4-ferrocene molecules on Au(111) is studied by STM for the presence of intra- and intermolecular correlations in the configurations of the four-pendant ferrocenyl moieties. A statistical analysis of STS images exploits the Pearson's linear correlation coefficient derived from changes in the molecular electron density across lateral positions in the molecular network as a measure of the intra- and intermolecular coupling and/or conjugation between adjacent equivalent molecular components. Density functional theory (DFT) calculation shows that these electron density changes can be assigned to conformational changes of the ferrocenyl units of the molecules. The methodology presented here can be extended to measure correlations in other 2D systems. © 2019 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Molecular parameters responsible for thermally activated transport in doped organic semiconductors
    • M. Schwarze, C. Gaul, R. Scholz, F. Bussolotti, A. Hofacker, K. S. Schellhammer, B. Nell, B. D. Naab, Z. Bao, D. Spoltore, K. Vandewal, J. Widmer, S. Kera, N. Ueno, F. Ortmann, K. Leo
    • Nature Materials 18, 242-248 (2019)
    • DOI   Abstract  

      Doped organic semiconductors typically exhibit a thermal activation of their electrical conductivity, whose physical origin is still under scientific debate. In this study, we disclose relationships between molecular parameters and the thermal activation energy (E A ) of the conductivity, revealing that charge transport is controlled by the properties of host–dopant integer charge transfer complexes (ICTCs) in efficiently doped organic semiconductors. At low doping concentrations, charge transport is limited by the Coulomb binding energy of ICTCs, which can be minimized by systematic modification of the charge distribution on the individual ions. The investigation of a wide variety of material systems reveals that static energetic disorder induced by ICTC dipole moments sets a general lower limit for E A at large doping concentrations. The impact of disorder can be reduced by adjusting the ICTC density and the intramolecular relaxation energy of host ions, allowing an increase of conductivity by many orders of magnitude. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.

      @ARTICLE{Schwarze2019242,
      author={Schwarze, M. and Gaul, C. and Scholz, R. and Bussolotti, F. and Hofacker, A. and Schellhammer, K.S. and Nell, B. and Naab, B.D. and Bao, Z. and Spoltore, D. and Vandewal, K. and Widmer, J. and Kera, S. and Ueno, N. and Ortmann, F. and Leo, K.},
      title={Molecular parameters responsible for thermally activated transport in doped organic semiconductors},
      journal={Nature Materials},
      year={2019},
      volume={18},
      number={3},
      pages={242-248},
      doi={10.1038/s41563-018-0277-0},
      note={cited By 38},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060809601&doi=10.1038%2fs41563-018-0277-0&partnerID=40&md5=c0df662b086e08611645bff185cfe69b},
      affiliation={Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany; Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany; Institute for Molecular Science, Department of Photo-Molecular Science, Myodaiji, Okazaki, Aichi, Japan; Department of Chemical Engineering, Stanford University, Stanford, CA, United States; Graduate School of Advanced Integration Science, Chiba University, Chiba, Japan; Institute for Materials Research (IMO), Hasselt University, Diepenbeek, Belgium; Heliatek GmbH, Dresden, Germany},
      abstract={Doped organic semiconductors typically exhibit a thermal activation of their electrical conductivity, whose physical origin is still under scientific debate. In this study, we disclose relationships between molecular parameters and the thermal activation energy (E A ) of the conductivity, revealing that charge transport is controlled by the properties of host–dopant integer charge transfer complexes (ICTCs) in efficiently doped organic semiconductors. At low doping concentrations, charge transport is limited by the Coulomb binding energy of ICTCs, which can be minimized by systematic modification of the charge distribution on the individual ions. The investigation of a wide variety of material systems reveals that static energetic disorder induced by ICTC dipole moments sets a general lower limit for E A at large doping concentrations. The impact of disorder can be reduced by adjusting the ICTC density and the intramolecular relaxation energy of host ions, allowing an increase of conductivity by many orders of magnitude. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.},
      document_type={Article},
      source={Scopus},
      }

  • ITO Work Function Tunability by Polarizable Chromophore Monolayers
    • A. Gankin, E. Mervinetsky, I. Alshanski, J. Buchwald, A. Dianat, R. Gutierrez, G. Cuniberti, R. Sfez, S. Yitzchaik
    • Langmuir 35, 2997-3004 (2019)
    • DOI   Abstract  

      The ability to tune the electronic properties of oxide-bearing semiconductors such as Si/SiO 2 or transparent metal oxides such as indium-tin oxide (ITO) is of great importance in both electronic and optoelectronic device applications. In this work, we describe a process that was conducted on n-type Si/SiO 2 and ITO to induce changes in the substrate work function (WF). The substrates were modified by a two-step synthesis comprising a covalent attachment of coupling agents‘ monolayer followed by in situ anchoring reactions of polarizable chromophores. The coupling agents and chromophores were chosen with opposite dipole orientations, which enabled the tunability of the substrates‘ WF. In the first step, two coupling agents with opposite molecular dipole were assembled. The coupling agent with a negative dipole induced a decrease in WF of modified substrates, while the coupling agent with a positive dipole produced an increase in WFs of both ITO and Si substrates. The second modification step consisted of in situ anchoring reaction of polarizable chromophores with opposite dipoles to the coupling layer. This modification led to an additional change in the WFs of both Si/SiO 2 and ITO substrates. The WF was measured by contact potential difference and modeled by density functional theory-based theoretical calculations of the WF for each of the assembly steps. A good fit was obtained between the calculated and experimental trends. This ability to design and tune the WF of ITO substrates was implemented in an organic electronic device with improved I-V characteristics in comparison to a bare ITO-based device. © 2019 American Chemical Society.

      @ARTICLE{Gankin20192997,
      author={Gankin, A. and Mervinetsky, E. and Alshanski, I. and Buchwald, J. and Dianat, A. and Gutierrez, R. and Cuniberti, G. and Sfez, R. and Yitzchaik, S.},
      title={ITO Work Function Tunability by Polarizable Chromophore Monolayers},
      journal={Langmuir},
      year={2019},
      volume={35},
      number={8},
      pages={2997-3004},
      doi={10.1021/acs.langmuir.8b03943},
      note={cited By 4},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061934171&doi=10.1021%2facs.langmuir.8b03943&partnerID=40&md5=ed7dd51abfaa10b8a65a59b71f8b9a4f},
      affiliation={Institute of Chemistry, Hebrew University of Jerusalem, Safra Campus, Givat Ram, Jerusalem, 91904, Israel; Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Safra Campus, Givat Ram, Jerusalem, 91904, Israel; Azrieli College of Engineering, Jerusalem, 9103501, Israel; Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany},
      abstract={The ability to tune the electronic properties of oxide-bearing semiconductors such as Si/SiO 2 or transparent metal oxides such as indium-tin oxide (ITO) is of great importance in both electronic and optoelectronic device applications. In this work, we describe a process that was conducted on n-type Si/SiO 2 and ITO to induce changes in the substrate work function (WF). The substrates were modified by a two-step synthesis comprising a covalent attachment of coupling agents' monolayer followed by in situ anchoring reactions of polarizable chromophores. The coupling agents and chromophores were chosen with opposite dipole orientations, which enabled the tunability of the substrates' WF. In the first step, two coupling agents with opposite molecular dipole were assembled. The coupling agent with a negative dipole induced a decrease in WF of modified substrates, while the coupling agent with a positive dipole produced an increase in WFs of both ITO and Si substrates. The second modification step consisted of in situ anchoring reaction of polarizable chromophores with opposite dipoles to the coupling layer. This modification led to an additional change in the WFs of both Si/SiO 2 and ITO substrates. The WF was measured by contact potential difference and modeled by density functional theory-based theoretical calculations of the WF for each of the assembly steps. A good fit was obtained between the calculated and experimental trends. This ability to design and tune the WF of ITO substrates was implemented in an organic electronic device with improved I-V characteristics in comparison to a bare ITO-based device. © 2019 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Strain and screening: Optical properties of a small-diameter carbon nanotube from first principles
    • C. Wagner, J. Schuster, A. Schleife
    • Physical Review B 99, 075140 (2019)
    • DOI   Abstract  

      Carbon nanotubes (CNTs) are a one-dimensional material system with intriguing physical properties that lead to emerging applications. While CNTs are unusually strain resistant compared to bulk materials, their optical-absorption spectrum is highly strain dependent. It is an open question, as to what extent this is attributed to strain-dependent (i) electronic single-particle transitions, (ii) dielectric screening, or (iii) atomic geometries including CNT radii. We use cutting-edge theoretical spectroscopy to explain strain-dependent electronic structure and optical properties of an (8,0) CNT. Quasiparticle effects are taken into account using Hedin’s GW approximation and excitonic effects are described by solving a Bethe-Salpeter-equation for the optical polarization function. This accurate first-principles approach allows us to identify an influence of strain on screening of the Coulomb electron-electron interaction and to quantify the impact on electronic structure and optical absorption of one-dimensional systems. We interpret our thoroughly converged results using an existing scaling relation and extend the use of this relation to strained CNTs. We show that it captures optical absorption with satisfactory accuracy, as long as screening, quasiparticle gap, and effective electron and hole masses of the strained CNT are known. © 2019 American Physical Society.

      @ARTICLE{Wagner2019,
      author={Wagner, C. and Schuster, J. and Schleife, A.},
      title={Strain and screening: Optical properties of a small-diameter carbon nanotube from first principles},
      journal={Physical Review B},
      year={2019},
      volume={99},
      number={7},
      doi={10.1103/PhysRevB.99.075140},
      art_number={075140},
      note={cited By 4},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061965955&doi=10.1103%2fPhysRevB.99.075140&partnerID=40&md5=475c52f453e41a693a4936f82c189e9e},
      affiliation={Technische Universität Chemnitz, Center for Microtechnologies, Reichenhainer Straße 70, Chemnitz, 09126, Germany; Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States; Fraunhofer Institute for Electronic Nano Systems (ENAS), Technologiecampus 3, Chemnitz, 09126, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States; National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States; Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, Dresden, 01328, Germany},
      abstract={Carbon nanotubes (CNTs) are a one-dimensional material system with intriguing physical properties that lead to emerging applications. While CNTs are unusually strain resistant compared to bulk materials, their optical-absorption spectrum is highly strain dependent. It is an open question, as to what extent this is attributed to strain-dependent (i) electronic single-particle transitions, (ii) dielectric screening, or (iii) atomic geometries including CNT radii. We use cutting-edge theoretical spectroscopy to explain strain-dependent electronic structure and optical properties of an (8,0) CNT. Quasiparticle effects are taken into account using Hedin's GW approximation and excitonic effects are described by solving a Bethe-Salpeter-equation for the optical polarization function. This accurate first-principles approach allows us to identify an influence of strain on screening of the Coulomb electron-electron interaction and to quantify the impact on electronic structure and optical absorption of one-dimensional systems. We interpret our thoroughly converged results using an existing scaling relation and extend the use of this relation to strained CNTs. We show that it captures optical absorption with satisfactory accuracy, as long as screening, quasiparticle gap, and effective electron and hole masses of the strained CNT are known. © 2019 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Copolymers of Diketopyrrolopyrrole and Benzothiadiazole: Design and Function from Simulations with Experimental Support
    • D. Raychev, R. D. Méndez López, A. Kiriy, G. Seifert, J. -U. Sommer, O. Guskova
    • Macromolecules 52, 904-914 (2019)
    • DOI   Abstract  

      Alternating block copolymers consisting of diketopyrrolopyrrole and benzothiadiazole electron acceptor units linked together via aromatic five-membered donor heterocycles are studied using a combination of computer simulation techniques and experiments. Four copolymers are modeled starting from their monomers to stacked macromolecules: with two different linkers – thiophene or furan, connecting electron-withdrawing core units – and two different alkyl substituents at lactam nitrogens of diketopyrrolopyrrole – linear dodecyl and branched 2-octyldodecyl chains. In our experiments, we aim at characterization of the optical and electrochemical properties of two copolymers with branched side chains differing in the linker, since as the literature survey shows the data published on these copolymers are very sparse. These properties can be easily interpreted and later compared with theoretical predictions. The results of simulations supported by experiments show that monomers of these polymers have very similar electronic and optical properties, and the main difference between them consists in various chain curvature defined by the linker. More curved furan-containing monomers and more stretched thiophene-linked molecules are characterized by different energetics of the stack formation and diverse in charge carrier mobilities. The branching of the side chains affects the planarity of the macromolecules, leads to longer π- π stacking distance and lamellar interval in the ordered arrays of polymers, and defines the stacking patterns of the conjugated backbones. The ambipolar transport is predicted for the majority of considered copolymer morphologies, and a quantitatively satisfactory agreement between experiment and computation is achieved. © 2019 American Chemical Society.

      @ARTICLE{Raychev2019904,
      author={Raychev, D. and Méndez López, R.D. and Kiriy, A. and Seifert, G. and Sommer, J.-U. and Guskova, O.},
      title={Copolymers of Diketopyrrolopyrrole and Benzothiadiazole: Design and Function from Simulations with Experimental Support},
      journal={Macromolecules},
      year={2019},
      volume={52},
      number={3},
      pages={904-914},
      doi={10.1021/acs.macromol.8b02500},
      note={cited By 4},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061632151&doi=10.1021%2facs.macromol.8b02500&partnerID=40&md5=79c4cd9b38eb63bba050ac0d1d1fc054},
      affiliation={Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, 01069, Germany; Institute of Macromolecular Chemistry, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Theoretical Chemistry, Technische Universität Dresden, Dresden, 01062, Germany; Institute of Theoretical Physics, Technische Universität Dresden, Zellescher Weg 17, Dresden, 01069, Germany},
      abstract={Alternating block copolymers consisting of diketopyrrolopyrrole and benzothiadiazole electron acceptor units linked together via aromatic five-membered donor heterocycles are studied using a combination of computer simulation techniques and experiments. Four copolymers are modeled starting from their monomers to stacked macromolecules: with two different linkers - thiophene or furan, connecting electron-withdrawing core units - and two different alkyl substituents at lactam nitrogens of diketopyrrolopyrrole - linear dodecyl and branched 2-octyldodecyl chains. In our experiments, we aim at characterization of the optical and electrochemical properties of two copolymers with branched side chains differing in the linker, since as the literature survey shows the data published on these copolymers are very sparse. These properties can be easily interpreted and later compared with theoretical predictions. The results of simulations supported by experiments show that monomers of these polymers have very similar electronic and optical properties, and the main difference between them consists in various chain curvature defined by the linker. More curved furan-containing monomers and more stretched thiophene-linked molecules are characterized by different energetics of the stack formation and diverse in charge carrier mobilities. The branching of the side chains affects the planarity of the macromolecules, leads to longer π- π stacking distance and lamellar interval in the ordered arrays of polymers, and defines the stacking patterns of the conjugated backbones. The ambipolar transport is predicted for the majority of considered copolymer morphologies, and a quantitatively satisfactory agreement between experiment and computation is achieved. © 2019 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • A review of numerical models for 3D woven composite reinforcements
    • T. Gereke, C. Cherif
    • Composite Structures 209, 60-66 (2019)
    • DOI   Abstract  

      In recent years, a new class of composite reinforcements has gained considerable attention: 3D woven fabrics. Their advantages in terms of reducing preforming steps and their resistance to impact and delamination have been clearly proven. However, relationships between fabric structure and composite properties are still largely unknown. Numerical models on different length scales were developed that capture the mechanical behavior of fabrics and their composites. This paper reviews models for 3D woven fabrics in the dry state and discusses results that were achieved with parametric studies. Special attention is given to the determination of the initial configuration of the 3D woven fabric model. The multi-filament character of yarns is best depicted with meso-scale approaches that describe the sub-yarn behavior with realistic models. Developed models can be used for further investigations, e. g. the optimization of fabric structure and forming processes. © 2018 Elsevier Ltd

      @ARTICLE{Gereke201960,
      author={Gereke, T. and Cherif, C.},
      title={A review of numerical models for 3D woven composite reinforcements},
      journal={Composite Structures},
      year={2019},
      volume={209},
      pages={60-66},
      doi={10.1016/j.compstruct.2018.10.085},
      note={cited By 30},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055735283&doi=10.1016%2fj.compstruct.2018.10.085&partnerID=40&md5=32f17c8aa9512e2b85a37525209f21e9},
      affiliation={Technische Universität Dresden, Institute of Textile Machinery and High Performance Material Technology and Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany},
      abstract={In recent years, a new class of composite reinforcements has gained considerable attention: 3D woven fabrics. Their advantages in terms of reducing preforming steps and their resistance to impact and delamination have been clearly proven. However, relationships between fabric structure and composite properties are still largely unknown. Numerical models on different length scales were developed that capture the mechanical behavior of fabrics and their composites. This paper reviews models for 3D woven fabrics in the dry state and discusses results that were achieved with parametric studies. Special attention is given to the determination of the initial configuration of the 3D woven fabric model. The multi-filament character of yarns is best depicted with meso-scale approaches that describe the sub-yarn behavior with realistic models. Developed models can be used for further investigations, e. g. the optimization of fabric structure and forming processes. © 2018 Elsevier Ltd},
      author_keywords={3D woven fabrics; Mechanical properties; Numerical analysis; Textiles},
      document_type={Review},
      source={Scopus},
      }

  • Swelling and shrinking in prestressed polymer gels: An incremental stress-diffusion analysis
    • M. Rossi, P. Nardinocchi, T. Wallmersperger
    • Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 475, 20190174 (2019)
    • DOI   Abstract  

      Polymer gels are porous fluid-saturated materials which can swell or shrink triggered by various stimuli. The swelling/shrinking-induced deformation can generate large stresses which may lead to the failure of the material. In the present research, a nonlinear stress-diffusion model is employed to investigate the stress and the deformation state arising in hydrated constrained polymer gels when subject to a varying chemical potential. Two different constraint configurations are taken into account: (i) elastic constraint along the thickness direction and (ii) plane elastic constraint. The first step entirely defines a compressed/tensed configuration. From there, an incremental chemo-mechanical analysis is presented. The derived model extends the classical linear poroelastic theory with respect to a prestressed configuration. Finally, the comparison between the analytical results obtained by the proposed model and a particular problem already discussed in literature for a stress-free gelmembrane (one-dimensional test case) will highlight the relevance of the derived model. © 2019 The Author(s) Published by the Royal Society. All rights reserved.

      @ARTICLE{Rossi2019,
      author={Rossi, M. and Nardinocchi, P. and Wallmersperger, T.},
      title={Swelling and shrinking in prestressed polymer gels: An incremental stress-diffusion analysis},
      journal={Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences},
      year={2019},
      volume={475},
      number={2230},
      doi={10.1098/rspa.2019.0174},
      art_number={20190174},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074779553&doi=10.1098%2frspa.2019.0174&partnerID=40&md5=a7803b3a96e0acae185412bb69476530},
      affiliation={Institute of Solid Mechanics, TU Dresden, George-Bähr-Straße 3c, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Hallwachsstraße 3, Dresden, 01069, Germany; Department of Structural and Geotechnical Engineering, Sapienza Università di Roma, via Eudossiana 18, Roma, 00184, Italy},
      abstract={Polymer gels are porous fluid-saturated materials which can swell or shrink triggered by various stimuli. The swelling/shrinking-induced deformation can generate large stresses which may lead to the failure of the material. In the present research, a nonlinear stress-diffusion model is employed to investigate the stress and the deformation state arising in hydrated constrained polymer gels when subject to a varying chemical potential. Two different constraint configurations are taken into account: (i) elastic constraint along the thickness direction and (ii) plane elastic constraint. The first step entirely defines a compressed/tensed configuration. From there, an incremental chemo-mechanical analysis is presented. The derived model extends the classical linear poroelastic theory with respect to a prestressed configuration. Finally, the comparison between the analytical results obtained by the proposed model and a particular problem already discussed in literature for a stress-free gelmembrane (one-dimensional test case) will highlight the relevance of the derived model. © 2019 The Author(s) Published by the Royal Society. All rights reserved.},
      author_keywords={Active materials; Incremental analysis; Polymer gels; Prestressed state; Stress-diffusion theory; Swelling/shrinking},
      document_type={Article},
      source={Scopus},
      }

  • Top dielectric induced ambipolarity in an n-channel dual-gated organic field effect transistor
    • K. Bairagi, E. Zuccatti, F. Calavalle, S. Catalano, S. Parui, R. Llopis, F. Ortmann, F. Casanova, L. E. Hueso
    • Journal of Materials Chemistry C 7, 10389-10393 (2019)
    • DOI   Abstract  

      The realization of both p-type and n-type operations in a single organic field effect transistor (OFET) is critical for simplifying the design of complex organic circuits. Typically, only p-type or n-type operation is realized in an OFET, while the respective counterpart is either suppressed by charge trapping or limited by the injection barrier with the electrodes. Here we show that only the presence of a top dielectric turns an n-type polymer semiconductor (N2200, Polyera ActiveInk™) into an ambipolar one, as detected from both bottom and top gated OFET operation. The effect is independent of the channel thickness and the top dielectric combinations. Variable temperature transfer characteristics show that both the electrons and holes can be equally transported through the bulk of the polymer semiconductor. © 2019 The Royal Society of Chemistry.

      @ARTICLE{Bairagi201910389,
      author={Bairagi, K. and Zuccatti, E. and Calavalle, F. and Catalano, S. and Parui, S. and Llopis, R. and Ortmann, F. and Casanova, F. and Hueso, L.E.},
      title={Top dielectric induced ambipolarity in an n-channel dual-gated organic field effect transistor},
      journal={Journal of Materials Chemistry C},
      year={2019},
      volume={7},
      number={33},
      pages={10389-10393},
      doi={10.1039/c9tc02912e},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071262778&doi=10.1039%2fc9tc02912e&partnerID=40&md5=fc97561394d7b09ff29de5c589b3e61a},
      affiliation={CIC NanoGUNE, San Sebastian, 20018, Spain; Center for Advancing Electronics Dresden, Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; IKERBASQUE, Basque Foundation for Science, Bilbao, 48013, Spain; IMEC, K. U. Leuven, Leuven, 3001, Belgium},
      abstract={The realization of both p-type and n-type operations in a single organic field effect transistor (OFET) is critical for simplifying the design of complex organic circuits. Typically, only p-type or n-type operation is realized in an OFET, while the respective counterpart is either suppressed by charge trapping or limited by the injection barrier with the electrodes. Here we show that only the presence of a top dielectric turns an n-type polymer semiconductor (N2200, Polyera ActiveInk™) into an ambipolar one, as detected from both bottom and top gated OFET operation. The effect is independent of the channel thickness and the top dielectric combinations. Variable temperature transfer characteristics show that both the electrons and holes can be equally transported through the bulk of the polymer semiconductor. © 2019 The Royal Society of Chemistry.},
      document_type={Article},
      source={Scopus},
      }

  • Engineering Kitaev exchange in stacked iridate layers: Impact of inter-layer species on in-plane magnetism
    • R. Yadav, M. S. Eldeeb, R. Ray, S. Aswartham, M. I. Sturza, S. Nishimoto, J. Van Den Brink, L. Hozoi
    • Chemical Science 10, 1866-1872 (2019)
    • DOI   Abstract  

      Novel functionalities may be achieved in oxide electronics by appropriate stacking of planar oxide layers of different metallic species, MOp and M′Oq. The simplest mechanism allowing the tailoring of the electronic states and physical properties of such heterostructures is of electrostatic nature – charge imbalance between the M and M′ cations. Here we clarify the effect of interlayer electrostatics on the anisotropic Kitaev exchange in H3LiIr2O6, a recently proposed realization of the Kitaev spin liquid. By quantum chemical calculations, we show that the precise position of H+ cations between magnetically active [LiIr2O6]3- honeycomb-like layers has a strong impact on the magnitude of Kitaev interactions. In particular, it is found that stacking with straight interlayer O-H-O links is detrimental to in-plane Kitaev exchange since coordination by a single H-ion of the O ligand implies an axial Coulomb potential at the O site and unfavorable polarization of the O 2p orbitals mediating the Ir-Ir interactions. Our results therefore provide valuable guidelines for the rational design of Kitaev quantum magnets, indicating unprecedented Kitaev interactions of ≈40 meV if the linear interlayer linkage is removed. © 2019 The Royal Society of Chemistry.

      @ARTICLE{Yadav20191866,
      author={Yadav, R. and Eldeeb, M.S. and Ray, R. and Aswartham, S. and Sturza, M.I. and Nishimoto, S. and Van Den Brink, J. and Hozoi, L.},
      title={Engineering Kitaev exchange in stacked iridate layers: Impact of inter-layer species on in-plane magnetism},
      journal={Chemical Science},
      year={2019},
      volume={10},
      number={6},
      pages={1866-1872},
      doi={10.1039/c8sc03018a},
      note={cited By 4},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061126828&doi=10.1039%2fc8sc03018a&partnerID=40&md5=cfd526f394f02d11c1c5ebc35f182504},
      affiliation={Leibniz Institute for Solid State and Materials Research, IFW Dresden, Helmholtzstr. 20, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Department of Physics, Technical University Dresden, Helmholtzstr. 10, Dresden, 01069, Germany},
      abstract={Novel functionalities may be achieved in oxide electronics by appropriate stacking of planar oxide layers of different metallic species, MOp and M′Oq. The simplest mechanism allowing the tailoring of the electronic states and physical properties of such heterostructures is of electrostatic nature - charge imbalance between the M and M′ cations. Here we clarify the effect of interlayer electrostatics on the anisotropic Kitaev exchange in H3LiIr2O6, a recently proposed realization of the Kitaev spin liquid. By quantum chemical calculations, we show that the precise position of H+ cations between magnetically active [LiIr2O6]3- honeycomb-like layers has a strong impact on the magnitude of Kitaev interactions. In particular, it is found that stacking with straight interlayer O-H-O links is detrimental to in-plane Kitaev exchange since coordination by a single H-ion of the O ligand implies an axial Coulomb potential at the O site and unfavorable polarization of the O 2p orbitals mediating the Ir-Ir interactions. Our results therefore provide valuable guidelines for the rational design of Kitaev quantum magnets, indicating unprecedented Kitaev interactions of ≈40 meV if the linear interlayer linkage is removed. © 2019 The Royal Society of Chemistry.},
      document_type={Article},
      source={Scopus},
      }

  • Modeling of the coadsorption of chloride and hydrogen ions on copper electrode surface
    • H. Yang, A. Dianat, M. Bobeth, G. Cuniberti
    • Journal of the Electrochemical Society 166, D3042-D3048 (2019)
    • DOI   Abstract  

      For manufacturing copper interconnects by the damscence technique, electrochemical deposition of copper on patterned sustrates requires several additives to achieve compact filling of trenches and vias, where chloride ions play a crucial role. In the highly acidic electrolyte, adsorption of chloride ions on copper is expected to compete with the adsorption of hydrogen, depending on the copper electrode potential. We propose a general phenomenological model of the coadsorption of two ion species which is supported by DFT calculations and show how the adsorption of one species can be described by the common Langmuir model with rescaled parameters depending on the concentration of the second species. Regarding the Cl–H+-system, corresponding model parameters are estimated by fitting radio tracer measurements of the chloride adsorption on copper reported in the literature. The data suggest that in a highly acidic solution (pH ≈ 0) the saturation surface density of chloride depends strongly on the electrode potential. With variation of the potential ESHE from -0.4 to +0.2 V, the saturation density changes by a factor of four. Within our model, such a potential dependence of the saturation density is explained by the presence of adsorbed hydrogen. © The Author(s) 2018. Published by ECS.

      @ARTICLE{Yang2019D3042,
      author={Yang, H. and Dianat, A. and Bobeth, M. and Cuniberti, G.},
      title={Modeling of the coadsorption of chloride and hydrogen ions on copper electrode surface},
      journal={Journal of the Electrochemical Society},
      year={2019},
      volume={166},
      number={1},
      pages={D3042-D3048},
      doi={10.1149/2.0061901jes},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063081413&doi=10.1149%2f2.0061901jes&partnerID=40&md5=1255c868c7b862de62bfe9d9b7fe591f},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden (CfAED), Dresden, 01069, Germany},
      abstract={For manufacturing copper interconnects by the damscence technique, electrochemical deposition of copper on patterned sustrates requires several additives to achieve compact filling of trenches and vias, where chloride ions play a crucial role. In the highly acidic electrolyte, adsorption of chloride ions on copper is expected to compete with the adsorption of hydrogen, depending on the copper electrode potential. We propose a general phenomenological model of the coadsorption of two ion species which is supported by DFT calculations and show how the adsorption of one species can be described by the common Langmuir model with rescaled parameters depending on the concentration of the second species. Regarding the Cl--H+-system, corresponding model parameters are estimated by fitting radio tracer measurements of the chloride adsorption on copper reported in the literature. The data suggest that in a highly acidic solution (pH ≈ 0) the saturation surface density of chloride depends strongly on the electrode potential. With variation of the potential ESHE from -0.4 to +0.2 V, the saturation density changes by a factor of four. Within our model, such a potential dependence of the saturation density is explained by the presence of adsorbed hydrogen. © The Author(s) 2018. Published by ECS.},
      document_type={Article},
      source={Scopus},
      }

  • Stabilization of aqueous graphene dispersions utilizing a biocompatible dispersant: a molecular dynamics study
    • S. Huang, A. Croy, V. Bezugly, G. Cuniberti
    • Physical Chemistry Chemical Physics 21, 24007-24016 (2019)
    • DOI   Abstract  

      Flavin mononucleotide sodium (FMNS) was recently reported as a highly efficient dispersant for the exfoliation of defect-free, few-layer, stabilized aqueous graphene dispersions. Most importantly, FMNS is innocuous and eco-friendly and can facilitate biomedical applications of graphene. Complementing those experimental studies, the influence of FMNS molecules on the aggregation behavior of graphene flakes in solution is investigated via all-atom molecular dynamics simulations. The stabilizing role of FMNS is demonstrated by the potential of mean force calculations for pairs of graphene flakes covered by FMNS molecules. These results indicate that the optimal amount ratio between FMNS molecules and carbon atoms in monolayer graphene is about 0.026 leading to a surface coverage of 0.34 FMNS molecules per nm2 on the graphene flakes. Overall the simulations support the high efficiency of FMNS as a surfactant compared to other surfactants. © 2019 the Owner Societies.

      @ARTICLE{Huang201924007,
      author={Huang, S. and Croy, A. and Bezugly, V. and Cuniberti, G.},
      title={Stabilization of aqueous graphene dispersions utilizing a biocompatible dispersant: a molecular dynamics study},
      journal={Physical Chemistry Chemical Physics},
      year={2019},
      volume={21},
      number={43},
      pages={24007-24016},
      doi={10.1039/c9cp04742e},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074674949&doi=10.1039%2fc9cp04742e&partnerID=40&md5=32e8e76766cf36484b517b0fa7535452},
      affiliation={Institute for Materials Science and Max Bergmann Center for Biomaterials, Technische Universität Dresden, Dresden, 01062, Germany; Life Science Inkubator Sachsen GmbH and Co. KG, Tatzberg 47, Dresden, 01307, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={Flavin mononucleotide sodium (FMNS) was recently reported as a highly efficient dispersant for the exfoliation of defect-free, few-layer, stabilized aqueous graphene dispersions. Most importantly, FMNS is innocuous and eco-friendly and can facilitate biomedical applications of graphene. Complementing those experimental studies, the influence of FMNS molecules on the aggregation behavior of graphene flakes in solution is investigated via all-atom molecular dynamics simulations. The stabilizing role of FMNS is demonstrated by the potential of mean force calculations for pairs of graphene flakes covered by FMNS molecules. These results indicate that the optimal amount ratio between FMNS molecules and carbon atoms in monolayer graphene is about 0.026 leading to a surface coverage of 0.34 FMNS molecules per nm2 on the graphene flakes. Overall the simulations support the high efficiency of FMNS as a surfactant compared to other surfactants. © 2019 the Owner Societies.},
      document_type={Article},
      source={Scopus},
      }

  • A zinc selective oxytocin based biosensor
    • E. Mervinetsky, I. Alshanski, K. K. Tadi, M. Hurevich, S. Yitzchaik, A. Dianat, J. Buchwald, R. Gutierrez, G. Cuniberti
    • Journal of Materials Chemistry B 8, 155-160 (2019)
    • DOI   Abstract  

      Oxytocin is a peptide hormone with high affinity to both Zn2+ and Cu2+ ions compared to other metal ions. This affinity makes oxytocin an attractive recognition layer for monitoring the levels of these essential ions in biofluids. Native oxytocin cannot differentiate between Cu2+ and Zn2+ ions and hence it is not useful for sensing Zn2+ in the presence of Cu2+. We elucidated the effect of the terminal amine group of oxytocin on the affinity toward Cu2+ using theoretical calculations. We designed a new Zn2+ selective oxytocin-based biosensor that utilizes the terminal amine for surface anchoring, also preventing the response to Cu2+. The biosensor shows exceptional selectivity and very high sensitivity to Zn2+ in impedimetric biosensing. This study shows for the first time an oxytocin derived sensor that can be used directly for sensing Zn2+ in the presence of Cu2+ This journal is © The Royal Society of Chemistry.

      @ARTICLE{Mervinetsky2019155,
      author={Mervinetsky, E. and Alshanski, I. and Tadi, K.K. and Hurevich, M. and Yitzchaik, S. and Dianat, A. and Buchwald, J. and Gutierrez, R. and Cuniberti, G.},
      title={A zinc selective oxytocin based biosensor},
      journal={Journal of Materials Chemistry B},
      year={2019},
      volume={8},
      number={1},
      pages={155-160},
      doi={10.1039/c9tb01932d},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076876611&doi=10.1039%2fc9tb01932d&partnerID=40&md5=d2f741c7c8c39940b277c5add88bf1ec},
      affiliation={Institute of Chemistry and the Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem, 91904, Israel; Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Oxytocin is a peptide hormone with high affinity to both Zn2+ and Cu2+ ions compared to other metal ions. This affinity makes oxytocin an attractive recognition layer for monitoring the levels of these essential ions in biofluids. Native oxytocin cannot differentiate between Cu2+ and Zn2+ ions and hence it is not useful for sensing Zn2+ in the presence of Cu2+. We elucidated the effect of the terminal amine group of oxytocin on the affinity toward Cu2+ using theoretical calculations. We designed a new Zn2+ selective oxytocin-based biosensor that utilizes the terminal amine for surface anchoring, also preventing the response to Cu2+. The biosensor shows exceptional selectivity and very high sensitivity to Zn2+ in impedimetric biosensing. This study shows for the first time an oxytocin derived sensor that can be used directly for sensing Zn2+ in the presence of Cu2+ This journal is © The Royal Society of Chemistry.},
      document_type={Article},
      source={Scopus},
      }

  • Quantum phonon transport in nanomaterials: Combining atomistic with non-equilibrium green’s function techniques
    • L. M. Sandonas, R. Gutierrez, A. Pecchia, A. Croy, G. Cuniberti
    • Entropy 21, 735 (2019)
    • DOI   Abstract  

      A crucial goal for increasing thermal energy harvesting will be to progress towards atomistic design strategies for smart nanodevices and nanomaterials. This requires the combination of computationally efficient atomisticmethodologies with quantum transport based approaches. Here, we review our recent work on this problem, by presenting selected applications of the PHONON tool to the description of phonon transport in nanostructured materials. The PHONON tool is a module developed as part of the Density-Functional Tight-Binding (DFTB) software platform. We discuss the anisotropic phonon band structure of selected puckered two-dimensional materials, helical and horizontal doping effects in the phonon thermal conductivity of boron nitride-carbon heteronanotubes, phonon filtering in molecular junctions, and a novel computational methodology to investigate time-dependent phonon transport at the atomistic level. These examples illustrate the versatility of our implementation of phonon transport in combination with density functional-based methods to address specific nanoscale functionalities, thus potentially allowing for designing novel thermal devices. © 2019 by the authors.

      @ARTICLE{Sandonas2019,
      author={Sandonas, L.M. and Gutierrez, R. and Pecchia, A. and Croy, A. and Cuniberti, G.},
      title={Quantum phonon transport in nanomaterials: Combining atomistic with non-equilibrium green's function techniques},
      journal={Entropy},
      year={2019},
      volume={21},
      number={8},
      doi={10.3390/e21080735},
      art_number={735},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070463687&doi=10.3390%2fe21080735&partnerID=40&md5=ea579f4728abb94d0e8fbce5e09036ac},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Consiglio Nazionale delle Ricerche, ISMN, Via Salaria km 29.6, Monterotondo, Rome, 00017, Italy; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Physics and Materials Science Research Unit, University of LuxembourgL-1511, Luxembourg},
      abstract={A crucial goal for increasing thermal energy harvesting will be to progress towards atomistic design strategies for smart nanodevices and nanomaterials. This requires the combination of computationally efficient atomisticmethodologies with quantum transport based approaches. Here, we review our recent work on this problem, by presenting selected applications of the PHONON tool to the description of phonon transport in nanostructured materials. The PHONON tool is a module developed as part of the Density-Functional Tight-Binding (DFTB) software platform. We discuss the anisotropic phonon band structure of selected puckered two-dimensional materials, helical and horizontal doping effects in the phonon thermal conductivity of boron nitride-carbon heteronanotubes, phonon filtering in molecular junctions, and a novel computational methodology to investigate time-dependent phonon transport at the atomistic level. These examples illustrate the versatility of our implementation of phonon transport in combination with density functional-based methods to address specific nanoscale functionalities, thus potentially allowing for designing novel thermal devices. © 2019 by the authors.},
      author_keywords={Density-functional tight binding; Green's functions; Landauer approach; Nanostructured materials; Phonon transport; Time-dependent transport},
      document_type={Review},
      source={Scopus},
      }

  • On-surface synthesis of nitrogen-doped nanographenes with 5-7 membered rings
    • D. Skidin, F. Eisenhut, M. Richter, S. Nikipar, J. Krüger, D. A. Ryndyk, R. Berger, G. Cuniberti, X. Feng, F. Moresco
    • Chemical Communications 55, 4731-4734 (2019)
    • DOI   Abstract  

      We report on the formation of nitrogen-doped nanographenes containing five- and seven-membered rings by thermally induced cyclodehydrogenation on the Au(111) surface. Using scanning tunneling microscopy and supported by calculations, we investigated the structure of the precursor and targets, as well as of intermediates. Scanning tunneling spectroscopy shows that the electronic properties of the target nanographenes are strongly influenced by the additional formation of non-hexagonal rings. © The Royal Society of Chemistry.

      @ARTICLE{Skidin20194731,
      author={Skidin, D. and Eisenhut, F. and Richter, M. and Nikipar, S. and Krüger, J. and Ryndyk, D.A. and Berger, R. and Cuniberti, G. and Feng, X. and Moresco, F.},
      title={On-surface synthesis of nitrogen-doped nanographenes with 5-7 membered rings},
      journal={Chemical Communications},
      year={2019},
      volume={55},
      number={32},
      pages={4731-4734},
      doi={10.1039/C9CC00276F},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064551398&doi=10.1039%2fC9CC00276F&partnerID=40&md5=14818b683d511b38717d8d1f92d8ae85},
      affiliation={Institute for Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Institute of Molecular Functional Materials, Department of Chemistry and Food Chemistry, TU Dresden, Dresden, 01062, Germany; Bremen Center for Computational Materials Science, Department of Physics, Universität Bremen, Bremen, 28359, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={We report on the formation of nitrogen-doped nanographenes containing five- and seven-membered rings by thermally induced cyclodehydrogenation on the Au(111) surface. Using scanning tunneling microscopy and supported by calculations, we investigated the structure of the precursor and targets, as well as of intermediates. Scanning tunneling spectroscopy shows that the electronic properties of the target nanographenes are strongly influenced by the additional formation of non-hexagonal rings. © The Royal Society of Chemistry.},
      document_type={Article},
      source={Scopus},
      }

  • Doping engineering of thermoelectric transport in BNC heteronanotubes
    • L. Medrano Sandonas, G. Cuba-Supanta, R. Gutierrez, C. V. Landauro, J. Rojas-Tapia, G. Cuniberti
    • Physical Chemistry Chemical Physics 21, 1904-1911 (2019)
    • DOI   Abstract  

      BNC heteronanotubes are promising materials for the design of nanoscale thermoelectric devices. In particular, the structural BN doping pattern can be exploited to control the electrical and thermal transport properties of BNC nanostructures. We here address the thermoelectric transport properties of (6,6)-BNC heteronanotubes with helical and horizontal BN doping patterns. For this, we use a density functional tight-binding method combined with the Green’s function technique. Our results show that the electron transmission is reduced and the electronic bandgap increased as a function of the BN concentration for different doping distribution patterns, so that (6,6)-BNC heteronanotubes become semiconducting with a tunable bandgap. The thermal conductance of helical (6,6)-BNC heteronanotubes, which is dominated by phonons, is weakly dependent on BN concentration in the range of 30-80%. Also, the Seebeck coefficient is enhanced by increasing the concentration of helical BN strips. In particular, helical (6,6)-BNC heteronanotubes with a high BN concentration (>20%) display a larger figure of merit compared to other doping distributions and, for a concentration of 50%, reach values up to 2.3 times and 3.4 times the corresponding values of a CNT at 300 K and 800 K, respectively. Our study yields new insights into the parameters tuning the thermoelectric efficiency and thus provides a starting point for designing thermoelectric devices based on BNC nanostructures. © 2019 the Owner Societies.

      @ARTICLE{MedranoSandonas20191904,
      author={Medrano Sandonas, L. and Cuba-Supanta, G. and Gutierrez, R. and Landauro, C.V. and Rojas-Tapia, J. and Cuniberti, G.},
      title={Doping engineering of thermoelectric transport in BNC heteronanotubes},
      journal={Physical Chemistry Chemical Physics},
      year={2019},
      volume={21},
      number={4},
      pages={1904-1911},
      doi={10.1039/c8cp05592k},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060400792&doi=10.1039%2fc8cp05592k&partnerID=40&md5=ac5927a11bf09cc7c42744d6f448fdd0},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Max Planck Institute, Physics of Complex Systems, Dresden, 01187, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Faculty of Physical Sciences, National University of San Marcos, P.O. Box 14-0149, Lima, 14, Peru; Centro de Investigaciones Tecnológicas, Biomédicas y Medioambientales (CIBTM), Bella Vista, Callao, Peru; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={BNC heteronanotubes are promising materials for the design of nanoscale thermoelectric devices. In particular, the structural BN doping pattern can be exploited to control the electrical and thermal transport properties of BNC nanostructures. We here address the thermoelectric transport properties of (6,6)-BNC heteronanotubes with helical and horizontal BN doping patterns. For this, we use a density functional tight-binding method combined with the Green's function technique. Our results show that the electron transmission is reduced and the electronic bandgap increased as a function of the BN concentration for different doping distribution patterns, so that (6,6)-BNC heteronanotubes become semiconducting with a tunable bandgap. The thermal conductance of helical (6,6)-BNC heteronanotubes, which is dominated by phonons, is weakly dependent on BN concentration in the range of 30-80%. Also, the Seebeck coefficient is enhanced by increasing the concentration of helical BN strips. In particular, helical (6,6)-BNC heteronanotubes with a high BN concentration (>20%) display a larger figure of merit compared to other doping distributions and, for a concentration of 50%, reach values up to 2.3 times and 3.4 times the corresponding values of a CNT at 300 K and 800 K, respectively. Our study yields new insights into the parameters tuning the thermoelectric efficiency and thus provides a starting point for designing thermoelectric devices based on BNC nanostructures. © 2019 the Owner Societies.},
      document_type={Article},
      source={Scopus},
      }

  • Immobilization of detonation nanodiamonds on macroscopic surfaces
    • S. Balakin, N. R. Dennison, B. Klemmed, J. Spohn, G. Cuniberti, L. Römhildt, J. Opitz
    • Applied Sciences (Switzerland) 9, 1064 (2019)
    • DOI   Abstract  

      Detonation nanodiamonds (NDs) are a novel class of carbon-based nanomaterials, and have received a great deal of attention in biomedical applications, due to their high biocompatibility, facile surface functionalization, and commercialized synthetic fabrication. We were able to transfer the NDs from large-size agglomerate suspensions to homogenous coatings. ND suspensions have been used in various techniques to coat on commercially available substrates of pure Ti and Si. Scanning electron microscopy (SEM) imaging and nanoindentation show that the densest and strongest coating of NDs was generated when using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide (EDC/NHS)-mediated coupling to macroscopic silanized surfaces. In the next step, the feasibility of DNA-mediated coupling of NDs on macroscopic surfaces is discussed using fluorescent microscopy and additional particle size distribution, as well as zeta potential measurements. This work compares different ND coating strategies and describes the straightforward technique of grafting single-stranded DNA onto carboxylated NDs via thioester bridges. © 2019 by the authors.

      @ARTICLE{Balakin2019,
      author={Balakin, S. and Dennison, N.R. and Klemmed, B. and Spohn, J. and Cuniberti, G. and Römhildt, L. and Opitz, J.},
      title={Immobilization of detonation nanodiamonds on macroscopic surfaces},
      journal={Applied Sciences (Switzerland)},
      year={2019},
      volume={9},
      number={6},
      doi={10.3390/app9061064},
      art_number={1064},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063737220&doi=10.3390%2fapp9061064&partnerID=40&md5=7baca2592ae003af2ba9b3ae6fa9852d},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, 01062, Germany; Fraunhofer Institute for Ceramic Technologies and Systems IKTS Material Diagnostics, Dresden, 01109, Germany; Physical Chemistry, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, 01062, Germany; Fraunhofer Institute for Ceramic Technologies and Systems IKTS Material Diagnostics, Leipzig, 04103, Germany},
      abstract={Detonation nanodiamonds (NDs) are a novel class of carbon-based nanomaterials, and have received a great deal of attention in biomedical applications, due to their high biocompatibility, facile surface functionalization, and commercialized synthetic fabrication. We were able to transfer the NDs from large-size agglomerate suspensions to homogenous coatings. ND suspensions have been used in various techniques to coat on commercially available substrates of pure Ti and Si. Scanning electron microscopy (SEM) imaging and nanoindentation show that the densest and strongest coating of NDs was generated when using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide (EDC/NHS)-mediated coupling to macroscopic silanized surfaces. In the next step, the feasibility of DNA-mediated coupling of NDs on macroscopic surfaces is discussed using fluorescent microscopy and additional particle size distribution, as well as zeta potential measurements. This work compares different ND coating strategies and describes the straightforward technique of grafting single-stranded DNA onto carboxylated NDs via thioester bridges. © 2019 by the authors.},
      author_keywords={Bio-conjugation; De-agglomeration; Detonation nanodiamonds; Fluorescent microscopy; Nanoindentation},
      document_type={Article},
      source={Scopus},
      }

2018

  • Inducing the controlled rotation of single o-MeO-DMBI molecules anchored on Au(111)
    • F. Eisenhut, J. Meyer, J. Krüger, R. Ohmann, G. Cuniberti, F. Moresco
    • Surface Science 678, 177-182 (2018)
    • DOI   Abstract  

      A key step towards building single molecule machines is to control the rotation of molecules and nanostructures step by step on a surface. Here, we used the tunneling electrons coming from the tip of a scanning tunneling microscope to achieve the controlled directed rotation of complex o-MeO-DMBI molecules. We studied the adsorption of single o-MeO-DMBI molecules on Au(111) by scanning tunneling microscopy at low temperature. The enantiomeric form of the molecule on the surface can be determined by imaging the molecule by STM at high bias voltage. We observed by lateral manipulation experiments that the molecules chemisorb on the surface and are anchored on Au(111) with an oxygen-gold bond via their methoxy‑group. Driven by inelastic tunneling electrons, o-MeO-DMBI molecules can controllably rotate, stepwise and unidirectional, either clockwise or counterclockwise depending on their enantiomeric form. © 2018

      @ARTICLE{Eisenhut2018177,
      author={Eisenhut, F. and Meyer, J. and Krüger, J. and Ohmann, R. and Cuniberti, G. and Moresco, F.},
      title={Inducing the controlled rotation of single o-MeO-DMBI molecules anchored on Au(111)},
      journal={Surface Science},
      year={2018},
      volume={678},
      pages={177-182},
      doi={10.1016/j.susc.2018.05.003},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047080490&doi=10.1016%2fj.susc.2018.05.003&partnerID=40&md5=56d788a09db44795f86308c70896aabc},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={A key step towards building single molecule machines is to control the rotation of molecules and nanostructures step by step on a surface. Here, we used the tunneling electrons coming from the tip of a scanning tunneling microscope to achieve the controlled directed rotation of complex o-MeO-DMBI molecules. We studied the adsorption of single o-MeO-DMBI molecules on Au(111) by scanning tunneling microscopy at low temperature. The enantiomeric form of the molecule on the surface can be determined by imaging the molecule by STM at high bias voltage. We observed by lateral manipulation experiments that the molecules chemisorb on the surface and are anchored on Au(111) with an oxygen-gold bond via their methoxy‑group. Driven by inelastic tunneling electrons, o-MeO-DMBI molecules can controllably rotate, stepwise and unidirectional, either clockwise or counterclockwise depending on their enantiomeric form. © 2018},
      author_keywords={Adsorption; Manipulation; Molecular rotor; Scanning tunneling microscopy (STM); Voltage pulses},
      document_type={Article},
      source={Scopus},
      }

  • First-principles investigation of Ag-, Co-, Cr-, Cu-, Fe-, Mn-, Ni-, Pd- and Rh-hexaaminobenzene 2D metal-organic frameworks
    • B. Mortazavi, M. Shahrokhi, M. Makaremi, G. Cuniberti, T. Rabczuk
    • Materials Today Energy 10, 336-342 (2018)
    • DOI   Abstract  

      Hexaaminobenzene (HAB)-derived two-dimensional metal−organic frameworks (MOFs) (Nature Energy 3(2018), 30–36) have most recently gained remarkable attentions as a novel class of two-dimensional (2D) materials, with outstanding performances for advanced energy storage systems. In the latest experimental advances, Ni-, Co- and Cu-HAB MOFs were synthesized in 2D forms, with high electrical conductivities and capacitances as well. Motivated by these experimental advances, we employed first-principles simulations to explore the mechanical, thermal stability and electronic properties of single-layer Ag-, Co-, Cr-, Cu-, Fe-, Mn-, Ni-, Pd- and Rh-HAB MOFs. Theoretical results reveal that Co-, Cr-, Fe-, Mn-, Ni-, Pd- and Rh-HAB nanosheets exhibit linear elasticity with considerable tensile strengths. Ab-initio molecular dynamics results confirm the high thermal stability of all studied nanomembranes. Co- and Fe-HAB monolayers show metallic behavior with low spin-polarization at the Fermi level. Single-layer Ag-, Cu-, Cr-, and Mn-HAB however yield perfect half-metallic behaviors, thus can be promising candidates for the spintronics. In contrast, Ni-, Pd- and Rh-HAB monolayers exhibit nonmagnetic metallic behavior. The insights provided by this investigation confirm the stability and highlight the outstanding physics of transition metal-HAB nanosheets, which are not only highly attractive for the energy storage systems, but may also serve for other advanced applications, like spintronics. © 2018 Elsevier Ltd

      @ARTICLE{Mortazavi2018336,
      author={Mortazavi, B. and Shahrokhi, M. and Makaremi, M. and Cuniberti, G. and Rabczuk, T.},
      title={First-principles investigation of Ag-, Co-, Cr-, Cu-, Fe-, Mn-, Ni-, Pd- and Rh-hexaaminobenzene 2D metal-organic frameworks},
      journal={Materials Today Energy},
      year={2018},
      volume={10},
      pages={336-342},
      doi={10.1016/j.mtener.2018.10.007},
      note={cited By 11},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055903192&doi=10.1016%2fj.mtener.2018.10.007&partnerID=40&md5=0d928d60544402964d33fc4f911b01c9},
      affiliation={Institute of Structural Mechanics, Bauhaus-Universität Weimar, Marienstr. 15, Weimar, D-99423, Germany; Department of Materials Science and Engineering, University of Toronto, 184 College Street, Suite 140, Toronto, ON M5S 3E4, Canada; Institute for Materials Science, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, D-01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Department of Computer Engineering, College of Computer and Information Sciences, King Saud University, Riyadh, Saudi Arabia},
      abstract={Hexaaminobenzene (HAB)-derived two-dimensional metal−organic frameworks (MOFs) (Nature Energy 3(2018), 30–36) have most recently gained remarkable attentions as a novel class of two-dimensional (2D) materials, with outstanding performances for advanced energy storage systems. In the latest experimental advances, Ni-, Co- and Cu-HAB MOFs were synthesized in 2D forms, with high electrical conductivities and capacitances as well. Motivated by these experimental advances, we employed first-principles simulations to explore the mechanical, thermal stability and electronic properties of single-layer Ag-, Co-, Cr-, Cu-, Fe-, Mn-, Ni-, Pd- and Rh-HAB MOFs. Theoretical results reveal that Co-, Cr-, Fe-, Mn-, Ni-, Pd- and Rh-HAB nanosheets exhibit linear elasticity with considerable tensile strengths. Ab-initio molecular dynamics results confirm the high thermal stability of all studied nanomembranes. Co- and Fe-HAB monolayers show metallic behavior with low spin-polarization at the Fermi level. Single-layer Ag-, Cu-, Cr-, and Mn-HAB however yield perfect half-metallic behaviors, thus can be promising candidates for the spintronics. In contrast, Ni-, Pd- and Rh-HAB monolayers exhibit nonmagnetic metallic behavior. The insights provided by this investigation confirm the stability and highlight the outstanding physics of transition metal-HAB nanosheets, which are not only highly attractive for the energy storage systems, but may also serve for other advanced applications, like spintronics. © 2018 Elsevier Ltd},
      author_keywords={2D materials; Energy storage; First-principles; MOFs},
      document_type={Article},
      source={Scopus},
      }

  • Polymerization driven monomer passage through monolayer chemical vapour deposition graphene
    • T. Zhang, Z. Liao, L. M. Sandonas, A. Dianat, X. Liu, P. Xiao, I. Amin, R. Gutierrez, T. Chen, E. Zschech, G. Cuniberti, R. Jordan
    • Nature Communications 9, 4051 (2018)
    • DOI   Abstract  

      Mass transport through graphene is receiving increasing attention due to the potential for molecular sieving. Experimental studies are mostly limited to the translocation of protons, ions, and water molecules, and results for larger molecules through graphene are rare. Here, we perform controlled radical polymerization with surface-anchored self-assembled initiator monolayer in a monomer solution with single-layer graphene separating the initiator from the monomer. We demonstrate that neutral monomers are able to pass through the graphene (via native defects) and increase the graphene defects ratio (Raman ID/IG) from ca. 0.09 to 0.22. The translocations of anionic and cationic monomers through graphene are significantly slower due to chemical interactions of monomers with the graphene defects. Interestingly, if micropatterned initiator-monolayers are used, the translocations of anionic monomers apparently cut the graphene sheet into congruent microscopic structures. The varied interactions between monomers and graphene defects are further investigated by quantum molecular dynamics simulations. © 2018, The Author(s).

      @ARTICLE{Zhang2018,
      author={Zhang, T. and Liao, Z. and Sandonas, L.M. and Dianat, A. and Liu, X. and Xiao, P. and Amin, I. and Gutierrez, R. and Chen, T. and Zschech, E. and Cuniberti, G. and Jordan, R.},
      title={Polymerization driven monomer passage through monolayer chemical vapour deposition graphene},
      journal={Nature Communications},
      year={2018},
      volume={9},
      number={1},
      doi={10.1038/s41467-018-06599-y},
      art_number={4051},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054315476&doi=10.1038%2fs41467-018-06599-y&partnerID=40&md5=0bb37ba4bb6e11a7cdeb051ba83a80dc},
      affiliation={Chair of Macromolecular Chemistry, Faculty of Chemistry and Food Chemistry, School of Science, Technische Universität Dresden, Mommsenstr. 4, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, 01062, Germany; Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, 01062, Germany; Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), Maria-Reiche-Straße 2, Dresden, 01109, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany; Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, Dresden, 01069, Germany; Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China; Junior Research Group Biosensing Surfaces, Leibniz Institute for Plasma Science and Technology, INP Greifswald e.V., Felix-Hausdorff-Strasse 2, Greifswald, 17489, Germany; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={Mass transport through graphene is receiving increasing attention due to the potential for molecular sieving. Experimental studies are mostly limited to the translocation of protons, ions, and water molecules, and results for larger molecules through graphene are rare. Here, we perform controlled radical polymerization with surface-anchored self-assembled initiator monolayer in a monomer solution with single-layer graphene separating the initiator from the monomer. We demonstrate that neutral monomers are able to pass through the graphene (via native defects) and increase the graphene defects ratio (Raman ID/IG) from ca. 0.09 to 0.22. The translocations of anionic and cationic monomers through graphene are significantly slower due to chemical interactions of monomers with the graphene defects. Interestingly, if micropatterned initiator-monolayers are used, the translocations of anionic monomers apparently cut the graphene sheet into congruent microscopic structures. The varied interactions between monomers and graphene defects are further investigated by quantum molecular dynamics simulations. © 2018, The Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Diversification of Device Platforms by Molecular Layers: Hybrid Sensing Platforms, Monolayer Doping, and Modeling
    • S. Yitzchaik, R. Gutierrez, G. Cuniberti, R. Yerushalmi
    • Langmuir 34, 14103-14123 (2018)
    • DOI   Abstract  

      Inorganic materials such as semiconductors, oxides, and metals are ubiquitous in a wide range of device technologies owing to the outstanding robustness and mature processing technologies available for such materials. However, while the important contribution of inorganic materials to the advancement of device technologies has been well established for decades, organic-inorganic hybrid device systems, which merge molecular functionalities with inorganic platforms, represent a newer domain that is rapidly evolving at an increasing pace. Such devices benefit from the great versatility and flexibility of the organic building blocks merged with the robustness of the inorganic platforms. Given the overwhelming wealth of literature covering various approaches for modifying and using inorganic devices, this feature article selectively highlights some of the advances made in the context of the diversification of devices by surface chemistry. Particular attention is given to oxide-semiconductor systems and metallic surfaces modified with organic monolayers. The inorganic device components, such as semiconductors, metals, and oxides, are modified by organic monolayers, which may serve as either active, static, or sacrificial components. We portray research directions within the broader field of organic-inorganic hybrid device systems that can be viewed as specific examples of the potential of such hybrid device systems given their comprehensive capabilities of design and diversification. Monolayer doping techniques where sacrificial organic monolayers are introduced into semiconducting elements are reviewed as a specific case, together with associated requirements for nanosystems, devices, and sensors for controlling doping levels and doping profiles on the nanometric scale. Another series of examples of the flexibility provided by the marriage of organic functional monolayers and inorganic device components are represented by a new class of biosensors, where the organic layer functionality is exploited in a functioning device for sensing. Considerations for relying on oxide-terminated semiconductors rather than the pristine semiconductor material as a platform both for processing and sensing are discussed. Finally, we cover aspects related to the use of various theoretical and computational approaches to model organic-inorganic systems. The main objectives of the topics covered here are (i) to present the advances made in each respective domain and (ii) to provide a comprehensive view of the potential uses of organic monolayers and self-assembly processes in the rapidly evolving field of molecular-inorganic hybrid device platforms and processing methodologies. The directions highlighted here provide a perspective on a future, not yet fully realized, integrated approach where organic monolayers are combined with inorganic platforms in order to obtain versatile, robust, and flexible systems with enhanced capabilities. Copyright © 2018 American Chemical Society.

      @ARTICLE{Yitzchaik201814103,
      author={Yitzchaik, S. and Gutierrez, R. and Cuniberti, G. and Yerushalmi, R.},
      title={Diversification of Device Platforms by Molecular Layers: Hybrid Sensing Platforms, Monolayer Doping, and Modeling},
      journal={Langmuir},
      year={2018},
      volume={34},
      number={47},
      pages={14103-14123},
      doi={10.1021/acs.langmuir.8b02369},
      note={cited By 9},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054783050&doi=10.1021%2facs.langmuir.8b02369&partnerID=40&md5=eaaf882781c718abe38e0fde124ffe01},
      affiliation={Institute of Chemistry, Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram Jerusalem, 91904, Israel; Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Inorganic materials such as semiconductors, oxides, and metals are ubiquitous in a wide range of device technologies owing to the outstanding robustness and mature processing technologies available for such materials. However, while the important contribution of inorganic materials to the advancement of device technologies has been well established for decades, organic-inorganic hybrid device systems, which merge molecular functionalities with inorganic platforms, represent a newer domain that is rapidly evolving at an increasing pace. Such devices benefit from the great versatility and flexibility of the organic building blocks merged with the robustness of the inorganic platforms. Given the overwhelming wealth of literature covering various approaches for modifying and using inorganic devices, this feature article selectively highlights some of the advances made in the context of the diversification of devices by surface chemistry. Particular attention is given to oxide-semiconductor systems and metallic surfaces modified with organic monolayers. The inorganic device components, such as semiconductors, metals, and oxides, are modified by organic monolayers, which may serve as either active, static, or sacrificial components. We portray research directions within the broader field of organic-inorganic hybrid device systems that can be viewed as specific examples of the potential of such hybrid device systems given their comprehensive capabilities of design and diversification. Monolayer doping techniques where sacrificial organic monolayers are introduced into semiconducting elements are reviewed as a specific case, together with associated requirements for nanosystems, devices, and sensors for controlling doping levels and doping profiles on the nanometric scale. Another series of examples of the flexibility provided by the marriage of organic functional monolayers and inorganic device components are represented by a new class of biosensors, where the organic layer functionality is exploited in a functioning device for sensing. Considerations for relying on oxide-terminated semiconductors rather than the pristine semiconductor material as a platform both for processing and sensing are discussed. Finally, we cover aspects related to the use of various theoretical and computational approaches to model organic-inorganic systems. The main objectives of the topics covered here are (i) to present the advances made in each respective domain and (ii) to provide a comprehensive view of the potential uses of organic monolayers and self-assembly processes in the rapidly evolving field of molecular-inorganic hybrid device platforms and processing methodologies. The directions highlighted here provide a perspective on a future, not yet fully realized, integrated approach where organic monolayers are combined with inorganic platforms in order to obtain versatile, robust, and flexible systems with enhanced capabilities. Copyright © 2018 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • A comparative analysis of symmetric diketopyrrolopyrrole-cored small conjugated molecules with aromatic flanks: From geometry to charge transport
    • D. Raychev, G. Seifert, J. -U. Sommer, O. Guskova
    • Journal of Computational Chemistry 39, 2526-2538 (2018)
    • DOI   Abstract  

      Diketopyrrolopyrrole (DPP) derivatives are promising compounds for application in organic electronics. Here, we investigate several symmetrical N-unsubstituted and N-methyl substituted DPPs which differ in the heteroatom in the aromatic flanks. The conformational, electronic, and optical properties are characterized for single molecules in vacuum or a solvent. The intermolecular interactions are evaluated for interacting dimers. Here, a number of stacking geometries is tested, and dimers with mutual orientation of the molecules corresponding to the minimal binding energies are determined. The predicted charge carrier mobilities for stacks having minimal binding energies corroborate experimentally measured values. We conclude that DFT prediction of such stacks is a promising and computationally inexpensive approach to a rough estimation of transport properties. Additionally, the super-cell of the experimentally resolved crystal structure is used to study the dynamics and to compute the charge transport along the hopping pathways. We discuss obtained high mobilities and relate them to the symmetry of DPP core. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

      @ARTICLE{Raychev20182526,
      author={Raychev, D. and Seifert, G. and Sommer, J.-U. and Guskova, O.},
      title={A comparative analysis of symmetric diketopyrrolopyrrole-cored small conjugated molecules with aromatic flanks: From geometry to charge transport},
      journal={Journal of Computational Chemistry},
      year={2018},
      volume={39},
      number={30},
      pages={2526-2538},
      doi={10.1002/jcc.25609},
      note={cited By 2},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054765258&doi=10.1002%2fjcc.25609&partnerID=40&md5=ec88323d12b92d1c81d35a53c7ffc616},
      affiliation={Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, Germany; Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, Germany; Theoretical Chemistry, Technische Universität Dresden, Dresden, 01062, Germany; Institute of Theoretical Physics, Technische Universität Dresden, Zellescher Weg 17, Dresden, 01069, Germany},
      abstract={Diketopyrrolopyrrole (DPP) derivatives are promising compounds for application in organic electronics. Here, we investigate several symmetrical N-unsubstituted and N-methyl substituted DPPs which differ in the heteroatom in the aromatic flanks. The conformational, electronic, and optical properties are characterized for single molecules in vacuum or a solvent. The intermolecular interactions are evaluated for interacting dimers. Here, a number of stacking geometries is tested, and dimers with mutual orientation of the molecules corresponding to the minimal binding energies are determined. The predicted charge carrier mobilities for stacks having minimal binding energies corroborate experimentally measured values. We conclude that DFT prediction of such stacks is a promising and computationally inexpensive approach to a rough estimation of transport properties. Additionally, the super-cell of the experimentally resolved crystal structure is used to study the dynamics and to compute the charge transport along the hopping pathways. We discuss obtained high mobilities and relate them to the symmetry of DPP core. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.},
      author_keywords={charge transport; DFT; diketopyrrolopyrrole; flanks; MD},
      document_type={Article},
      source={Scopus},
      }

  • Strong Effect of Hydrogen Order on Magnetic Kitaev Interactions in H3LiIr2 O6
    • R. Yadav, R. Ray, M. S. Eldeeb, S. Nishimoto, L. Hozoi, J. Van Den Brink
    • Physical Review Letters 121, 197203 (2018)
    • DOI   Abstract  

      Very recently a quantum liquid was reported to form in H3LiIr2O6, an iridate proposed to be a close realization of the Kitaev honeycomb model. To test this assertion we perform detailed quantum chemistry calculations to determine the magnetic interactions between Ir moments. We find that weakly bond dependent ferromagnetic Kitaev exchange dominates over other couplings, but still is substantially lower than in Na2IrO3. This reduction is caused by the peculiar position of the interlayer species: removing hydrogen cations next to a Ir2O2 plaquette increases the Kitaev exchange by more than a factor of 3 on the corresponding Ir-Ir link. Consequently, any lack of hydrogen order will have a drastic effect on the magnetic interactions and strongly promote spin disordering. © 2018 American Physical Society.

      @ARTICLE{Yadav2018,
      author={Yadav, R. and Ray, R. and Eldeeb, M.S. and Nishimoto, S. and Hozoi, L. and Van Den Brink, J.},
      title={Strong Effect of Hydrogen Order on Magnetic Kitaev Interactions in H3LiIr2 O6},
      journal={Physical Review Letters},
      year={2018},
      volume={121},
      number={19},
      doi={10.1103/PhysRevLett.121.197203},
      art_number={197203},
      note={cited By 19},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056518199&doi=10.1103%2fPhysRevLett.121.197203&partnerID=40&md5=396fad1c07cd192db8929fcb94cf3fdf},
      affiliation={Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Department of Physics, Technical University Dresden, Dresden, 01062, Germany},
      abstract={Very recently a quantum liquid was reported to form in H3LiIr2O6, an iridate proposed to be a close realization of the Kitaev honeycomb model. To test this assertion we perform detailed quantum chemistry calculations to determine the magnetic interactions between Ir moments. We find that weakly bond dependent ferromagnetic Kitaev exchange dominates over other couplings, but still is substantially lower than in Na2IrO3. This reduction is caused by the peculiar position of the interlayer species: removing hydrogen cations next to a Ir2O2 plaquette increases the Kitaev exchange by more than a factor of 3 on the corresponding Ir-Ir link. Consequently, any lack of hydrogen order will have a drastic effect on the magnetic interactions and strongly promote spin disordering. © 2018 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • How do immobilised cell-adhesive Arg–Gly–Asp-containing peptides behave at the PAA brush surface?
    • O. Guskova, V. Savchenko, U. König, P. Uhlmann, J. -U. Sommer
    • Molecular Simulation 44, 1325-1337 (2018)
    • DOI   Abstract  

      Bio-engineered surfaces that aim to induce normal cell behaviour in vitro need to ‘mimic’ the extracellular matrix in a way that allows cell adhesion. In this computational work, several model cell-binding peptides with a minimal cell-adhesive Arg–Gly–Asp sequence are investigated in the bulk as well as immobilised on a soft surface. For this reason, a combination of density functional theory and all-atom MD simulations is applied. The major goal of the modelling is to characterise the accessibility of the cell-recognition motif on the functionalised soft polymer surface. As a reference system, the behaviour of three peptide sequences is preliminarily studied in explicit water simulations. From the analysis of the MD trajectories, the solvent accessible surface area, the distribution of water molecules around peptide groups, the secondary structure and the thermodynamics of hydration are evaluated. Furthermore, each peptide is immobilised on the surface of a homopolymer poly(acrylic acid) brush. During MD simulations, all three peptides approach closely toward PAA brush, and their surface accessibility is characterised. Although the peptides are adsorbed onto the brush, they are not hidden by the polymer strands, with RGD unit accessible on the surface and available for guided cell adhesion. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

      @ARTICLE{Guskova20181325,
      author={Guskova, O. and Savchenko, V. and König, U. and Uhlmann, P. and Sommer, J.-U.},
      title={How do immobilised cell-adhesive Arg–Gly–Asp-containing peptides behave at the PAA brush surface?},
      journal={Molecular Simulation},
      year={2018},
      volume={44},
      number={16},
      pages={1325-1337},
      doi={10.1080/08927022.2018.1502429},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052052394&doi=10.1080%2f08927022.2018.1502429&partnerID=40&md5=935428c7a0c7afa026ee3d2c6e4a885b},
      affiliation={Leibniz Institut für Polymerforschung Dresden e.V., Dresden, Germany; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany; Fakultät Umweltwissenschaften, Technische Universität Dresden, Dresden, Germany; Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE, United States; Institut für Theoretische Physik, Technische Universität Dresden, Dresden, Germany},
      abstract={Bio-engineered surfaces that aim to induce normal cell behaviour in vitro need to ‘mimic’ the extracellular matrix in a way that allows cell adhesion. In this computational work, several model cell-binding peptides with a minimal cell-adhesive Arg–Gly–Asp sequence are investigated in the bulk as well as immobilised on a soft surface. For this reason, a combination of density functional theory and all-atom MD simulations is applied. The major goal of the modelling is to characterise the accessibility of the cell-recognition motif on the functionalised soft polymer surface. As a reference system, the behaviour of three peptide sequences is preliminarily studied in explicit water simulations. From the analysis of the MD trajectories, the solvent accessible surface area, the distribution of water molecules around peptide groups, the secondary structure and the thermodynamics of hydration are evaluated. Furthermore, each peptide is immobilised on the surface of a homopolymer poly(acrylic acid) brush. During MD simulations, all three peptides approach closely toward PAA brush, and their surface accessibility is characterised. Although the peptides are adsorbed onto the brush, they are not hidden by the polymer strands, with RGD unit accessible on the surface and available for guided cell adhesion. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.},
      author_keywords={density functional theory; molecular dynamics simulation; PAA brush; RGD peptide; thermodynamics of hydration},
      document_type={Article},
      source={Scopus},
      }

  • Time-dependent framework for energy and charge currents in nanoscale systems
    • T. Lehmann, A. Croy, R. Gutiérrez, G. Cuniberti
    • Chemical Physics 514, 176-182 (2018)
    • DOI   Abstract  

      The calculation of time-dependent charge and energy currents in nanoscale systems is a challenging task. Nevertheless it is crucial for gaining a deep understanding of the relevant processes at the nanoscale. We extend the auxiliary-mode approach for time-dependent charge transport to allow for the calculation of energy currents for arbitrary time dependencies. We apply the approach to two illustrative examples, a single-level system and a benzene ring, demonstrating its usefulness for a wide range of problems beyond simple toy models, such as molecular devices. © 2018 Elsevier B.V.

      @ARTICLE{Lehmann2018176,
      author={Lehmann, T. and Croy, A. and Gutiérrez, R. and Cuniberti, G.},
      title={Time-dependent framework for energy and charge currents in nanoscale systems},
      journal={Chemical Physics},
      year={2018},
      volume={514},
      pages={176-182},
      doi={10.1016/j.chemphys.2018.01.011},
      note={cited By 4},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040933262&doi=10.1016%2fj.chemphys.2018.01.011&partnerID=40&md5=18e35e84dfc2d92de43154f90476c061},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={The calculation of time-dependent charge and energy currents in nanoscale systems is a challenging task. Nevertheless it is crucial for gaining a deep understanding of the relevant processes at the nanoscale. We extend the auxiliary-mode approach for time-dependent charge transport to allow for the calculation of energy currents for arbitrary time dependencies. We apply the approach to two illustrative examples, a single-level system and a benzene ring, demonstrating its usefulness for a wide range of problems beyond simple toy models, such as molecular devices. © 2018 Elsevier B.V.},
      author_keywords={Charge current; Energy current; Non-adiabatic; Time-dependent},
      document_type={Article},
      source={Scopus},
      }

  • Thermal Decoherence and Disorder Effects on Chiral-Induced Spin Selectivity
    • E. Díaz, F. Domínguez-Adame, R. Gutierrez, G. Cuniberti, V. Mujica
    • Journal of Physical Chemistry Letters 9, 5753-5758 (2018)
    • DOI   Abstract  

      We use a nonlinear master equation formalism to account for thermal and disorder effects on spin-dependent electron transport in helical organic molecules coupled to two ideal leads. The inclusion of these two effects has important consequences in understanding the observed length and temperature dependence of spin polarization in experiments, which cannot be accounted for in a purely coherent tunneling model. Our approach considers a tight-binding helical Hamiltonian with disordered onsite energies to describe the resulting electronic states when low-frequency interacting modes break the electron coherence. The high-frequency fluctuating counterpart of these interactions, typical of intramolecular modes, is included by means of temperature-dependent thermally activated transfer probabilities in the master equation, which lead to hopping between localized states. We focus on the spin-dependent conductance and the spin-polarization in the linear regime (low voltage), which are analyzed as a function of the molecular length and the temperature of the system. Our results at room temperature agree well with experiments because our model predicts that the degree of spin-polarization increases for longer molecules. Also, this effect is temperature-dependent because thermal excitation competes with disorder-induced Anderson localization. We conclude that a transport mechanism based on thermally activated hopping in a disordered system can account for the unexpected behavior of the spin polarization. © 2018 American Chemical Society.

      @ARTICLE{Díaz20185753,
      author={Díaz, E. and Domínguez-Adame, F. and Gutierrez, R. and Cuniberti, G. and Mujica, V.},
      title={Thermal Decoherence and Disorder Effects on Chiral-Induced Spin Selectivity},
      journal={Journal of Physical Chemistry Letters},
      year={2018},
      volume={9},
      number={19},
      pages={5753-5758},
      doi={10.1021/acs.jpclett.8b02196},
      note={cited By 10},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053891550&doi=10.1021%2facs.jpclett.8b02196&partnerID=40&md5=2cf3e4e1e8d053f4dff09d3b877acab8},
      affiliation={GISC, Departamento de Física de Materiales, Universidad Complutense, Madrid, E-28040, Spain; Institute for Materials Science, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, United States},
      abstract={We use a nonlinear master equation formalism to account for thermal and disorder effects on spin-dependent electron transport in helical organic molecules coupled to two ideal leads. The inclusion of these two effects has important consequences in understanding the observed length and temperature dependence of spin polarization in experiments, which cannot be accounted for in a purely coherent tunneling model. Our approach considers a tight-binding helical Hamiltonian with disordered onsite energies to describe the resulting electronic states when low-frequency interacting modes break the electron coherence. The high-frequency fluctuating counterpart of these interactions, typical of intramolecular modes, is included by means of temperature-dependent thermally activated transfer probabilities in the master equation, which lead to hopping between localized states. We focus on the spin-dependent conductance and the spin-polarization in the linear regime (low voltage), which are analyzed as a function of the molecular length and the temperature of the system. Our results at room temperature agree well with experiments because our model predicts that the degree of spin-polarization increases for longer molecules. Also, this effect is temperature-dependent because thermal excitation competes with disorder-induced Anderson localization. We conclude that a transport mechanism based on thermally activated hopping in a disordered system can account for the unexpected behavior of the spin polarization. © 2018 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Electronic transport through defective semiconducting carbon nanotubes
    • F. Teichert, A. Zienert, J. Schuster, M. Schreiber
    • Journal of Physics Communications 2, 105012 (2018)
    • DOI   Abstract  

      We investigate the electronic transport properties of semiconducting (m, n) carbon nanotubes (CNTs) on the mesoscopic length scale with arbitrarily distributed realistic defects. The study is done by performing quantum transport calculations based on recursive Green’s function techniques and an underlying density-functional-based tight-binding model for the description of the electronic structure. Zigzag CNTs as well as chiral CNTs of different diameter are considered. Different defects are exemplarily represented by monovacancies and divacancies. We show the energy-dependent transmission and the temperature-dependent conductance as a function of the number of defects. In the limit of many defetcs, the transport is described by strong localization. Corresponding localization lengths are calculated (energy dependent and temperature dependent) and systematically compared for a large number of CNTs. It is shown, that a distinction by (m−n)mod 3 has to be drawn in order to classify CNTs with different bandgaps. Besides this, the localization length for a given defect probability per unit cell depends linearly on the CNT diameter, but not on the CNT chirality. Finally, elastic mean free paths in the diffusive regime are computed for the limit of few defects, yielding qualitatively same statements. © 2018 The Author(s).

      @ARTICLE{Teichert2018,
      author={Teichert, F. and Zienert, A. and Schuster, J. and Schreiber, M.},
      title={Electronic transport through defective semiconducting carbon nanotubes},
      journal={Journal of Physics Communications},
      year={2018},
      volume={2},
      number={10},
      doi={10.1088/2399-6528/aae4cb},
      art_number={105012},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070487465&doi=10.1088%2f2399-6528%2faae4cb&partnerID=40&md5=8ced67a24b1295bef618443eb8eb8f6e},
      affiliation={Institute of Physics, Chemnitz University of Technology, Chemnitz, 09107, Germany; Center for Microtechnologies, Chemnitz University of Technology, Chemnitz, 09107, Germany; Fraunhofer Institute for Electronic Nano Systems (ENAS), Chemnitz, 09126, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={We investigate the electronic transport properties of semiconducting (m, n) carbon nanotubes (CNTs) on the mesoscopic length scale with arbitrarily distributed realistic defects. The study is done by performing quantum transport calculations based on recursive Green’s function techniques and an underlying density-functional-based tight-binding model for the description of the electronic structure. Zigzag CNTs as well as chiral CNTs of different diameter are considered. Different defects are exemplarily represented by monovacancies and divacancies. We show the energy-dependent transmission and the temperature-dependent conductance as a function of the number of defects. In the limit of many defetcs, the transport is described by strong localization. Corresponding localization lengths are calculated (energy dependent and temperature dependent) and systematically compared for a large number of CNTs. It is shown, that a distinction by (m−n)mod 3 has to be drawn in order to classify CNTs with different bandgaps. Besides this, the localization length for a given defect probability per unit cell depends linearly on the CNT diameter, but not on the CNT chirality. Finally, elastic mean free paths in the diffusive regime are computed for the limit of few defects, yielding qualitatively same statements. © 2018 The Author(s).},
      author_keywords={Carbon nanotube (CNT); Defect; Density-functional-based tight binding (DFTB); Elastic mean free path; Electronic transport; Recursive Greenʼs function formalism (RGF); Strong localization},
      document_type={Article},
      source={Scopus},
      }

  • Tuning the conductance of a molecular wire by the interplay of donor and acceptor units
    • D. Skidin, T. Erdmann, S. Nikipar, F. Eisenhut, J. Krüger, F. Günther, S. Gemming, A. Kiriy, B. Voit, D. A. Ryndyk, C. Joachim, F. Moresco, G. Cuniberti
    • Nanoscale 10, 17131-17139 (2018)
    • DOI   Abstract  

      We investigate the conductance of optimized donor-acceptor-donor molecular wires obtained by on-surface synthesis on the Au(111) surface. A careful balance between acceptors and donors is achieved using a diketopyrrolopyrrole acceptor and two thiophene donors per unit along the wire. Scanning tunneling microscopy imaging, spectroscopy, and conductance measurements done by pulling a single molecular wire at one end are presented. We show that the conductance of the obtained wires is among the highest reported so far in a tunneling transport regime, with an inverse decay length of 0.17 Å−1. Using complex band structure calculations, different donor and acceptor groups are discussed, showing how a balanced combination of donor and acceptor units along the wire can further minimize the decay of the tunneling current with length. © The Royal Society of Chemistry.

      @ARTICLE{Skidin201817131,
      author={Skidin, D. and Erdmann, T. and Nikipar, S. and Eisenhut, F. and Krüger, J. and Günther, F. and Gemming, S. and Kiriy, A. and Voit, B. and Ryndyk, D.A. and Joachim, C. and Moresco, F. and Cuniberti, G.},
      title={Tuning the conductance of a molecular wire by the interplay of donor and acceptor units},
      journal={Nanoscale},
      year={2018},
      volume={10},
      number={36},
      pages={17131-17139},
      doi={10.1039/c8nr05031g},
      note={cited By 2},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054036347&doi=10.1039%2fc8nr05031g&partnerID=40&md5=f9b2aea21dadc867acfb338b665690d5},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01069, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Leibniz-Institut für Polymerforschung Dresden e.V., Dresden, 01069, Germany; Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, Dresden, 01328, Germany; Institute of Physics, TU Chemnitz, Chemnitz, 09107, Germany; Bremen Center for Computational Materials Science, Department of Physics, Universität Bremen, Bremen, 28359, Germany; GNS and MANA Satellite, CEMES, CNRS, 29 rue J. Marvig, Toulouse Cedex, 31055, France; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={We investigate the conductance of optimized donor-acceptor-donor molecular wires obtained by on-surface synthesis on the Au(111) surface. A careful balance between acceptors and donors is achieved using a diketopyrrolopyrrole acceptor and two thiophene donors per unit along the wire. Scanning tunneling microscopy imaging, spectroscopy, and conductance measurements done by pulling a single molecular wire at one end are presented. We show that the conductance of the obtained wires is among the highest reported so far in a tunneling transport regime, with an inverse decay length of 0.17 Å−1. Using complex band structure calculations, different donor and acceptor groups are discussed, showing how a balanced combination of donor and acceptor units along the wire can further minimize the decay of the tunneling current with length. © The Royal Society of Chemistry.},
      document_type={Article},
      source={Scopus},
      }

  • Enhanced Magnetoresistance in Chiral Molecular Junctions
    • V. V. Maslyuk, R. Gutierrez, A. Dianat, V. Mujica, G. Cuniberti
    • Journal of Physical Chemistry Letters 9, 5453-5459 (2018)
    • DOI   Abstract  

      Chirality-induced spin selectivity (CISS) is a recently discovered effect, whose precise microscopic origin has not yet been fully elucidated; it seems, however, clear that spin-orbit interaction plays a pivotal role. Various model Hamiltonian approaches have been proposed, suggesting a close connection between spin selectivity and filtering and helical symmetry. However, first-principles studies revealing the influence of chirality on the spin polarization are missing. To clearly demonstrate the influence of the helical conformation on the spin polarization properties, we have carried out spin-dependent Density-Functional Theory (DFT) based transport calculations for a model molecular system. It consists of α-helix and β-strand conformations of an oligo-glycine peptide, which is bonded to a nickel electrode and to a gold electrode in a two-terminal setup, similar to a molecular junction or a local probe, for example, in STM or AFM configurations. We have found that the α-helix conformation displays a spin polarization, calculated through the intrinsic magneto-resistance of the junction, about 100-1000 times larger than the linear β-strand, clearly demonstrating the crucial role played by the molecular helical geometry on the enhancement of spin polarization associated with the CISS effect. Copyright © 2018 American Chemical Society.

      @ARTICLE{Maslyuk20185453,
      author={Maslyuk, V.V. and Gutierrez, R. and Dianat, A. and Mujica, V. and Cuniberti, G.},
      title={Enhanced Magnetoresistance in Chiral Molecular Junctions},
      journal={Journal of Physical Chemistry Letters},
      year={2018},
      volume={9},
      number={18},
      pages={5453-5459},
      doi={10.1021/acs.jpclett.8b02360},
      note={cited By 31},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053719884&doi=10.1021%2facs.jpclett.8b02360&partnerID=40&md5=79b97c828a89c413fe8bad24e0ce3adf},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden University of Technology, Dresden, 01062, Germany; Arizona State University, School of Molecular Sciences, PO Box 871604, Tempe, AZ 85287-1604, United States; Dresden Center for Computational Materials Science, Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Chirality-induced spin selectivity (CISS) is a recently discovered effect, whose precise microscopic origin has not yet been fully elucidated; it seems, however, clear that spin-orbit interaction plays a pivotal role. Various model Hamiltonian approaches have been proposed, suggesting a close connection between spin selectivity and filtering and helical symmetry. However, first-principles studies revealing the influence of chirality on the spin polarization are missing. To clearly demonstrate the influence of the helical conformation on the spin polarization properties, we have carried out spin-dependent Density-Functional Theory (DFT) based transport calculations for a model molecular system. It consists of α-helix and β-strand conformations of an oligo-glycine peptide, which is bonded to a nickel electrode and to a gold electrode in a two-terminal setup, similar to a molecular junction or a local probe, for example, in STM or AFM configurations. We have found that the α-helix conformation displays a spin polarization, calculated through the intrinsic magneto-resistance of the junction, about 100-1000 times larger than the linear β-strand, clearly demonstrating the crucial role played by the molecular helical geometry on the enhancement of spin polarization associated with the CISS effect. Copyright © 2018 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Enhanced Magnetoresistance in Chiral Molecular Junctions
    • V. V. Maslyuk, R. Gutierrez, A. Dianat, V. Mujica, G. Cuniberti
    • The journal of physical chemistry letters 9, 5453-5459 (2018)
    • DOI   Abstract  

      Chirality-induced spin selectivity (CISS) is a recently discovered effect, whose precise microscopic origin has not yet been fully elucidated; it seems, however, clear that spin-orbit interaction plays a pivotal role. Various model Hamiltonian approaches have been proposed, suggesting a close connection between spin selectivity and filtering and helical symmetry. However, first-principles studies revealing the influence of chirality on the spin polarization are missing. To clearly demonstrate the influence of the helical conformation on the spin polarization properties, we have carried out spin-dependent Density-Functional Theory (DFT) based transport calculations for a model molecular system. It consists of α-helix and β-strand conformations of an oligo-glycine peptide, which is bonded to a nickel electrode and to a gold electrode in a two-terminal setup, similar to a molecular junction or a local probe, for example, in STM or AFM configurations. We have found that the α-helix conformation displays a spin polarization, calculated through the intrinsic magneto-resistance of the junction, about 100-1000 times larger than the linear β-strand, clearly demonstrating the crucial role played by the molecular helical geometry on the enhancement of spin polarization associated with the CISS effect.

      @ARTICLE{Maslyuk20185453,
      author={Maslyuk, V.V. and Gutierrez, R. and Dianat, A. and Mujica, V. and Cuniberti, G.},
      title={Enhanced Magnetoresistance in Chiral Molecular Junctions},
      journal={The journal of physical chemistry letters},
      year={2018},
      volume={9},
      number={18},
      pages={5453-5459},
      doi={10.1021/acs.jpclett.8b02360},
      note={cited By 1},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053510806&doi=10.1021%2facs.jpclett.8b02360&partnerID=40&md5=a66aa20f90f745666968512ca78c3799},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, Dresden University of Technology, Dresden, 01062, Germany; Arizona State University, School of Molecular Sciences, PO Box 871604, Tempe, Arizona 85287-1604, United States; Dresden Center for Computational Materials Science and Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Chirality-induced spin selectivity (CISS) is a recently discovered effect, whose precise microscopic origin has not yet been fully elucidated; it seems, however, clear that spin-orbit interaction plays a pivotal role. Various model Hamiltonian approaches have been proposed, suggesting a close connection between spin selectivity and filtering and helical symmetry. However, first-principles studies revealing the influence of chirality on the spin polarization are missing. To clearly demonstrate the influence of the helical conformation on the spin polarization properties, we have carried out spin-dependent Density-Functional Theory (DFT) based transport calculations for a model molecular system. It consists of α-helix and β-strand conformations of an oligo-glycine peptide, which is bonded to a nickel electrode and to a gold electrode in a two-terminal setup, similar to a molecular junction or a local probe, for example, in STM or AFM configurations. We have found that the α-helix conformation displays a spin polarization, calculated through the intrinsic magneto-resistance of the junction, about 100-1000 times larger than the linear β-strand, clearly demonstrating the crucial role played by the molecular helical geometry on the enhancement of spin polarization associated with the CISS effect.},
      document_type={Article},
      source={Scopus},
      }

  • Growth kinetics and morphological analysis of homoepitaxial GaAs fins by theory and experiment
    • M. Albani, L. Ghisalberti, R. Bergamaschini, M. Friedl, M. Salvalaglio, A. Voigt, F. Montalenti, G. Tütüncüoglu, A. M. I. Fontcuberta, L. Miglio
    • Physical Review Materials 2, 093404 (2018)
    • DOI   Abstract  

      Nanoscale membranes have emerged as a new class of vertical nanostructures that enable the integration of horizontal networks of III-V nanowires on a chip. To generalize this method to the whole family of III-Vs, progress in the understanding of the membrane formation by selective area epitaxy in oxide slits is needed, in particular for different slit orientations. Here, it is demonstrated that the shape is primarily driven by the growth kinetics rather than determined by surface energy minimization as commonly occurs for faceted nanostructures. To this end, a phase-field model simulating the shape evolution during growth is devised, in agreement with the experimental findings for any slit orientations, even when the vertical membranes turn into multifaceted fins. This makes it possible to reverseengineer the facet-dependent incorporation times, which were so far unknown, even for common low-index facets. The compelling reproduction of the experimental morphologies demonstrates the reliability of the growth model and offers a general method to determine microscopic kinetic parameters governing out-of-equilibrium three-dimensional growth. © 2018 American Physical Society.

      @ARTICLE{Albani2018,
      author={Albani, M. and Ghisalberti, L. and Bergamaschini, R. and Friedl, M. and Salvalaglio, M. and Voigt, A. and Montalenti, F. and Tütüncüoglu, G. and Fontcuberta, A.M.I. and Miglio, L.},
      title={Growth kinetics and morphological analysis of homoepitaxial GaAs fins by theory and experiment},
      journal={Physical Review Materials},
      year={2018},
      volume={2},
      number={9},
      doi={10.1103/PhysRevMaterials.2.093404},
      art_number={093404},
      note={cited By 18},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059614245&doi=10.1103%2fPhysRevMaterials.2.093404&partnerID=40&md5=232196bfbf3bc10a2d0a07f673924eae},
      affiliation={L-NESS and Dept. of Materials Science, Università di Milano-Bicocca, Milano, 20125, Italy; Laboratory of Semiconductor Materials, École Polytechnique Fédérale de Lausanne, EPFL, Lausanne, 1015, Switzerland; Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Filler Laboratory, Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, United States},
      abstract={Nanoscale membranes have emerged as a new class of vertical nanostructures that enable the integration of horizontal networks of III-V nanowires on a chip. To generalize this method to the whole family of III-Vs, progress in the understanding of the membrane formation by selective area epitaxy in oxide slits is needed, in particular for different slit orientations. Here, it is demonstrated that the shape is primarily driven by the growth kinetics rather than determined by surface energy minimization as commonly occurs for faceted nanostructures. To this end, a phase-field model simulating the shape evolution during growth is devised, in agreement with the experimental findings for any slit orientations, even when the vertical membranes turn into multifaceted fins. This makes it possible to reverseengineer the facet-dependent incorporation times, which were so far unknown, even for common low-index facets. The compelling reproduction of the experimental morphologies demonstrates the reliability of the growth model and offers a general method to determine microscopic kinetic parameters governing out-of-equilibrium three-dimensional growth. © 2018 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Microscopic field-theoretical approach for mixtures of active and passive particles
    • F. Alaimo, A. Voigt
    • Physical Review E 98, 032605 (2018)
    • DOI   Abstract  

      We consider a phase field crystal modeling approach for mixtures of interacting active and passive particles in two dimensions. The approach allows us to describe generic properties for such heterogeneous systems within a continuum model. We validate the approach by reproducing experimental results, as well as results obtained with agent-based simulations. The approach is valid for the whole spectrum from highly dilute suspensions of passive particles and interacting active particles in a dense background of passive particles. However, we concentrate only on the extreme cases, because for the situation with similar fractions of active and passive particles emerging structures are hard to analyze and experimental results are missing. We analyze in detail enhanced crystallization due to the presence of active particles, how collective migration is affected by a disordered environment, and laning states, which are globally nematic but polar within each lane. © 2018 American Physical Society.

      @ARTICLE{Alaimo2018,
      author={Alaimo, F. and Voigt, A.},
      title={Microscopic field-theoretical approach for mixtures of active and passive particles},
      journal={Physical Review E},
      year={2018},
      volume={98},
      number={3},
      doi={10.1103/PhysRevE.98.032605},
      art_number={032605},
      note={cited By 9},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053431731&doi=10.1103%2fPhysRevE.98.032605&partnerID=40&md5=c623a9ee9724a8a4dc390b72f310cda6},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany; Center of Systems Biology Dresden (CSBD), Pfotenhauerstr. 108, Dresden, 01307, Germany},
      abstract={We consider a phase field crystal modeling approach for mixtures of interacting active and passive particles in two dimensions. The approach allows us to describe generic properties for such heterogeneous systems within a continuum model. We validate the approach by reproducing experimental results, as well as results obtained with agent-based simulations. The approach is valid for the whole spectrum from highly dilute suspensions of passive particles and interacting active particles in a dense background of passive particles. However, we concentrate only on the extreme cases, because for the situation with similar fractions of active and passive particles emerging structures are hard to analyze and experimental results are missing. We analyze in detail enhanced crystallization due to the presence of active particles, how collective migration is affected by a disordered environment, and laning states, which are globally nematic but polar within each lane. © 2018 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Atomistic Framework for Time-Dependent Thermal Transport
    • L. Medrano Sandonas, A. Croy, R. Gutierrez, G. Cuniberti
    • Journal of Physical Chemistry C 122, 21062-21068 (2018)
    • DOI   Abstract  

      Phonons play a major role for the performance of nanoscale devices and consequently a detailed understanding of phonon dynamics is required. Using an auxiliary-mode approach, which has successfully been applied for the case of electrons, we develop a new method to numerically describe time-dependent phonon transport. This method allows one to gain insight into the behavior of local vibrations in molecular junctions, which are driven by time-dependent temperature differences between thermal baths. Exemplarily, we apply the method to study the nonequilibrium dynamics of quantum heat transport in an one-dimensional atomic chain as well as in realistic molecular junctions made of polyacetylene and polyethylene chains, in which the vibrational structure of the junction is described at the density functional theory level. We calculate the transient energies and heat currents and compare the latter to the standard Landauer approach in thermal equilibrium. We show that the auxiliary-mode representation is a powerful and versatile tool to study time-dependent thermal transport in nanoscale systems. © 2018 American Chemical Society.

      @ARTICLE{MedranoSandonas201821062,
      author={Medrano Sandonas, L. and Croy, A. and Gutierrez, R. and Cuniberti, G.},
      title={Atomistic Framework for Time-Dependent Thermal Transport},
      journal={Journal of Physical Chemistry C},
      year={2018},
      volume={122},
      number={36},
      pages={21062-21068},
      doi={10.1021/acs.jpcc.8b06598},
      note={cited By 2},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052315007&doi=10.1021%2facs.jpcc.8b06598&partnerID=40&md5=1461b678ee8f02c1d5229fa56f5d5f3b},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany},
      abstract={Phonons play a major role for the performance of nanoscale devices and consequently a detailed understanding of phonon dynamics is required. Using an auxiliary-mode approach, which has successfully been applied for the case of electrons, we develop a new method to numerically describe time-dependent phonon transport. This method allows one to gain insight into the behavior of local vibrations in molecular junctions, which are driven by time-dependent temperature differences between thermal baths. Exemplarily, we apply the method to study the nonequilibrium dynamics of quantum heat transport in an one-dimensional atomic chain as well as in realistic molecular junctions made of polyacetylene and polyethylene chains, in which the vibrational structure of the junction is described at the density functional theory level. We calculate the transient energies and heat currents and compare the latter to the standard Landauer approach in thermal equilibrium. We show that the auxiliary-mode representation is a powerful and versatile tool to study time-dependent thermal transport in nanoscale systems. © 2018 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Thermodynamically consistent three-dimensional electrochemical model for polymeric membranes
    • M. Rossi, T. Wallmersperger
    • Electrochimica Acta 283, 1323-1338 (2018)
    • DOI   Abstract  

      In this paper, the behavior of an electrochemical thin polymeric film sandwiched between porous electrodes and under input voltage (potentiostatic) conditions is numerically investigated. Thin polymeric membranes, such as Nafion, are widely used in micro-batteries and proton-exchange-membrane fuel cells. A three-dimensional continuum-based multi-field formulation for thin polymeric membranes is presented. The model is applied to configurations of the type electrode-membrane-electrode in order to represent the core of a characteristic electrochemical device. Various three-dimensional geometries are considered. The phenomena modeled within the polymeric membrane are (i) ion transport (chemical field) and (ii) electrical field. The field equations, i.e. the Poisson-Nernst-Planck equations, are determined by inserting the thermodynamically consistent constitutive equations within the balance equations of the electrochemical problem. Suitable initial and boundary conditions have to be imposed in order to solve the system of partial differential equations. In particular, the phenomena modeled at the membrane/electrode interface are (i) the electrochemical kinetics of the chemical reaction and (ii) the polarization effects. Time-dependent numerical simulations for potentiostatic conditions are performed within a finite element framework. It is shown that the presented fully coupled multi-field model reproduces, within a simulation framework, the behavior of electrochemical cells. In fact, the model is capable of well predicting the space and time evolution of the main electrochemical parameters as well as catching multi-dimensional effects. The presented model can be regarded as a starting point to develop further research concerning an electro-chemo-mechanical model in order to well understand the stress distribution which arises in polymeric membranes during operating conditions. © 2018 Elsevier Ltd

      @ARTICLE{Rossi20181323,
      author={Rossi, M. and Wallmersperger, T.},
      title={Thermodynamically consistent three-dimensional electrochemical model for polymeric membranes},
      journal={Electrochimica Acta},
      year={2018},
      volume={283},
      pages={1323-1338},
      doi={10.1016/j.electacta.2018.06.174},
      note={cited By 10},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050159805&doi=10.1016%2fj.electacta.2018.06.174&partnerID=40&md5=d522da5281c20fc0838b594357efa07b},
      affiliation={Institute of Solid Mechanics, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={In this paper, the behavior of an electrochemical thin polymeric film sandwiched between porous electrodes and under input voltage (potentiostatic) conditions is numerically investigated. Thin polymeric membranes, such as Nafion, are widely used in micro-batteries and proton-exchange-membrane fuel cells. A three-dimensional continuum-based multi-field formulation for thin polymeric membranes is presented. The model is applied to configurations of the type electrode-membrane-electrode in order to represent the core of a characteristic electrochemical device. Various three-dimensional geometries are considered. The phenomena modeled within the polymeric membrane are (i) ion transport (chemical field) and (ii) electrical field. The field equations, i.e. the Poisson-Nernst-Planck equations, are determined by inserting the thermodynamically consistent constitutive equations within the balance equations of the electrochemical problem. Suitable initial and boundary conditions have to be imposed in order to solve the system of partial differential equations. In particular, the phenomena modeled at the membrane/electrode interface are (i) the electrochemical kinetics of the chemical reaction and (ii) the polarization effects. Time-dependent numerical simulations for potentiostatic conditions are performed within a finite element framework. It is shown that the presented fully coupled multi-field model reproduces, within a simulation framework, the behavior of electrochemical cells. In fact, the model is capable of well predicting the space and time evolution of the main electrochemical parameters as well as catching multi-dimensional effects. The presented model can be regarded as a starting point to develop further research concerning an electro-chemo-mechanical model in order to well understand the stress distribution which arises in polymeric membranes during operating conditions. © 2018 Elsevier Ltd},
      author_keywords={Electrochemical cell; Finite elements; Thermodynamically based model; Thin membranes; Transport theory},
      document_type={Article},
      source={Scopus},
      }

  • Electronic Resonances and Gap Stabilization of Higher Acenes on a Gold Surface
    • J. Krüger, F. Eisenhut, D. Skidin, T. Lehmann, D. A. Ryndyk, G. Cuniberti, F. García, J. M. Alonso, E. Guitián, D. Pérez, D. Peña, G. Trinquier, J. -P. Malrieu, F. Moresco, C. Joachim
    • ACS Nano 12, 8506-8511 (2018)
    • DOI   Abstract  

      On-surface synthesis provides a powerful method for the generation of long acene molecules, making possible the detailed investigation of the electronic properties of single higher acenes on a surface. By means of scanning tunneling microscopy and spectroscopy combined with theoretical considerations, we discuss the polyradical character of the ground state of higher acenes as a function of the number of linearly fused benzene rings. We present energy and spatial mapping of the tunneling resonances of hexacene, heptacene, and decacene, and discuss the role of molecular orbitals in the observed tunneling conductance maps. We show that the energy gap between the first electronic tunneling resonances below and above the Fermi energy stabilizes to a finite value, determined by a first diradical electronic perturbative contribution to the polyacene electronic ground state. Up to decacene, the main contributor to the ground state of acenes remains the lowest-energy closed-shell electronic configuration. © 2018 American Chemical Society.

      @ARTICLE{Krüger20188506,
      author={Krüger, J. and Eisenhut, F. and Skidin, D. and Lehmann, T. and Ryndyk, D.A. and Cuniberti, G. and García, F. and Alonso, J.M. and Guitián, E. and Pérez, D. and Peña, D. and Trinquier, G. and Malrieu, J.-P. and Moresco, F. and Joachim, C.},
      title={Electronic Resonances and Gap Stabilization of Higher Acenes on a Gold Surface},
      journal={ACS Nano},
      year={2018},
      volume={12},
      number={8},
      pages={8506-8511},
      doi={10.1021/acsnano.8b04046},
      note={cited By 16},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052332523&doi=10.1021%2facsnano.8b04046&partnerID=40&md5=6503c2899f79167f842c3b71e52628c3},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Bremen Center for Computational Materials Science (BCCMS), Universität Bremen, Bremen, 28359, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Centro de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, Santiago de Compostela, 15782, Spain; Laboratoire de Chimie et Physique Quantiques, IRSAMC-CNRS-UMR5626, Université Paul-Sabatier (Toulouse III), Toulouse Cedex 4, 31062, France; Centre d'Élaboration de Matériaux et d'Études Structurale (CEMES), UPR 8011 CNRS, Nanosciences Group and MANA Satellite, 29 Rue J. Marvig, P.O. Box 94347, Toulouse, 31055, France},
      abstract={On-surface synthesis provides a powerful method for the generation of long acene molecules, making possible the detailed investigation of the electronic properties of single higher acenes on a surface. By means of scanning tunneling microscopy and spectroscopy combined with theoretical considerations, we discuss the polyradical character of the ground state of higher acenes as a function of the number of linearly fused benzene rings. We present energy and spatial mapping of the tunneling resonances of hexacene, heptacene, and decacene, and discuss the role of molecular orbitals in the observed tunneling conductance maps. We show that the energy gap between the first electronic tunneling resonances below and above the Fermi energy stabilizes to a finite value, determined by a first diradical electronic perturbative contribution to the polyacene electronic ground state. Up to decacene, the main contributor to the ground state of acenes remains the lowest-energy closed-shell electronic configuration. © 2018 American Chemical Society.},
      author_keywords={acenes; deoxygenation; energy gap; molecular orbitals; molecular resonances; on-surface synthesis; scanning tunneling spectroscopy},
      document_type={Article},
      source={Scopus},
      }

  • Hexacene generated on passivated silicon
    • F. Eisenhut, J. Krüger, D. Skidin, S. Nikipar, J. M. Alonso, E. Guitián, D. Pérez, D. A. Ryndyk, D. Peña, F. Moresco, G. Cuniberti
    • Nanoscale 10, 12582-12587 (2018)
    • DOI   Abstract  

      On-surface synthesis represents a successful strategy to obtain designed molecular structures on an ultra-clean metal substrate. While metal surfaces are known to favor adsorption, diffusion, and chemical bonding between molecular groups, on-surface synthesis on non-metallic substrates would allow the electrical decoupling of the resulting molecule from the surface, favoring application to electronics and spintronics. Here, we demonstrate the on-surface generation of hexacene by surface-assisted reduction on a H-passivated Si(001) surface. The reaction, observed by scanning tunneling microscopy and spectroscopy, is probably driven by the formation of Si-O complexes at dangling bond defects. Supported by density functional theory calculations, we investigate the interaction of hexacene with the passivated silicon surface, and with single silicon dangling bonds. © The Royal Society of Chemistry.

      @ARTICLE{Eisenhut201812582,
      author={Eisenhut, F. and Krüger, J. and Skidin, D. and Nikipar, S. and Alonso, J.M. and Guitián, E. and Pérez, D. and Ryndyk, D.A. and Peña, D. and Moresco, F. and Cuniberti, G.},
      title={Hexacene generated on passivated silicon},
      journal={Nanoscale},
      year={2018},
      volume={10},
      number={26},
      pages={12582-12587},
      doi={10.1039/c8nr03422b},
      note={cited By 4},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049863961&doi=10.1039%2fc8nr03422b&partnerID=40&md5=b0203d0742a1ad90ba5f4ec5b4202d47},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01069, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Centro de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Departamento de Química Orgánica, Universidade de Santiago de Compostela, Santiago de Compostela, 15782, Spain; Bremen Center for Computational Materials Science (BCCMS), Universität Bremen, Bremen, 28359, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01069, Germany},
      abstract={On-surface synthesis represents a successful strategy to obtain designed molecular structures on an ultra-clean metal substrate. While metal surfaces are known to favor adsorption, diffusion, and chemical bonding between molecular groups, on-surface synthesis on non-metallic substrates would allow the electrical decoupling of the resulting molecule from the surface, favoring application to electronics and spintronics. Here, we demonstrate the on-surface generation of hexacene by surface-assisted reduction on a H-passivated Si(001) surface. The reaction, observed by scanning tunneling microscopy and spectroscopy, is probably driven by the formation of Si-O complexes at dangling bond defects. Supported by density functional theory calculations, we investigate the interaction of hexacene with the passivated silicon surface, and with single silicon dangling bonds. © The Royal Society of Chemistry.},
      document_type={Article},
      source={Scopus},
      }

  • Self-Assembled Two-Dimensional Supramolecular Networks Characterized by Scanning Tunneling Microscopy and Spectroscopy in Air and under Vacuum
    • B. Naydenov, S. Torsney, A. S. Bonilla, M. El Garah, A. Ciesielski, A. Gualandi, L. Mengozzi, P. G. Cozzi, R. Gutierrez, P. Samorì, G. Cuniberti, J. J. Boland
    • Langmuir 34, 7698-7707 (2018)
    • DOI   Abstract  

      We combine ambient (air) and ultrahigh vacuum (UHV) scanning tunneling microscopy (STM) and spectroscopy (STS) investigations together with density functional theory (DFT) calculations to gain a subnanometer insight into the structure and dynamic of two-dimensional (2D) surface-supported molecular networks. The planar tetraferrocene-porphyrin molecules employed in this study undergo spontaneous self-assembly via the formation of hydrogen bonded networks at the gold substrate-solution interface. To mimic liquid phase ambient deposition conditions, film formation was accomplished in UHV by electro-spraying a solution of the molecule in chloroform onto an Au(111) substrate, thereby providing access to the full spectroscopic capabilities of STM that can be hardly attained under ambient conditions. We show that molecular assembly on Au (111) is identical in films prepared under the two different conditions, and in good agreement with the theoretical predictions. However, we observe the contrast found for a given STM bias condition to be different in ambient and UHV conditions despite the similarity of the structures, and we propose possible origins of the different imaging contrast. This approach could be valuable for the thorough characterization of surface systems that involve large molecules and are prepared mainly in ambient conditions. © 2018 American Chemical Society.

      @ARTICLE{Naydenov20187698,
      author={Naydenov, B. and Torsney, S. and Bonilla, A.S. and El Garah, M. and Ciesielski, A. and Gualandi, A. and Mengozzi, L. and Cozzi, P.G. and Gutierrez, R. and Samorì, P. and Cuniberti, G. and Boland, J.J.},
      title={Self-Assembled Two-Dimensional Supramolecular Networks Characterized by Scanning Tunneling Microscopy and Spectroscopy in Air and under Vacuum},
      journal={Langmuir},
      year={2018},
      volume={34},
      number={26},
      pages={7698-7707},
      doi={10.1021/acs.langmuir.8b01374},
      note={cited By 2},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048568384&doi=10.1021%2facs.langmuir.8b01374&partnerID=40&md5=8f599314ecd99ddf1eb6f76b5421e97c},
      affiliation={Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), School of Chemistry, Trinity College Dublin, I-Dublin-2, Ireland; Institute for Materials Sciences, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Université de Strasbourg, CNRS, ISIS, 8 alleé Gaspard Monge, Strasbourg, 67000, France; Dipartimento di Chimica G. Ciamician, Alma Mater Studiorum Università di Bologna, Via Selmi 2, Bologna, 40126, Italy; Dresden Center for Computational Materials Science (DCCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={We combine ambient (air) and ultrahigh vacuum (UHV) scanning tunneling microscopy (STM) and spectroscopy (STS) investigations together with density functional theory (DFT) calculations to gain a subnanometer insight into the structure and dynamic of two-dimensional (2D) surface-supported molecular networks. The planar tetraferrocene-porphyrin molecules employed in this study undergo spontaneous self-assembly via the formation of hydrogen bonded networks at the gold substrate-solution interface. To mimic liquid phase ambient deposition conditions, film formation was accomplished in UHV by electro-spraying a solution of the molecule in chloroform onto an Au(111) substrate, thereby providing access to the full spectroscopic capabilities of STM that can be hardly attained under ambient conditions. We show that molecular assembly on Au (111) is identical in films prepared under the two different conditions, and in good agreement with the theoretical predictions. However, we observe the contrast found for a given STM bias condition to be different in ambient and UHV conditions despite the similarity of the structures, and we propose possible origins of the different imaging contrast. This approach could be valuable for the thorough characterization of surface systems that involve large molecules and are prepared mainly in ambient conditions. © 2018 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Pressure-induced dimerization and valence bond crystal formation in the Kitaev-Heisenberg magnet α-RuCl3
    • G. Bastien, G. Garbarino, R. Yadav, F. J. Martinez-Casado, R. Beltrán Rodríguez, Q. Stahl, M. Kusch, S. P. Limandri, R. Ray, P. Lampen-Kelley, D. G. Mandrus, S. E. Nagler, M. Roslova, A. Isaeva, T. Doert, L. Hozoi, A. U. B. Wolter, B. Büchner, J. Geck, J. Van Den Brink
    • Physical Review B 97, 241108 (2018)
    • DOI   Abstract  

      Magnetization and high-resolution x-ray diffraction measurements of the Kitaev-Heisenberg material α-RuCl3 reveal a pressure-induced crystallographic and magnetic phase transition at a hydrostatic pressure of p∼0.2 GPa. This structural transition into a triclinic phase is characterized by a very strong dimerization of the Ru-Ru bonds, accompanied by a collapse of the magnetic susceptibility. Ab initio quantum-chemistry calculations disclose a pressure-induced enhancement of the direct 4d-4d bonding on particular Ru-Ru links, causing a sharp increase of the antiferromagnetic exchange interactions. These combined experimental and computational data show that the Kitaev spin-liquid phase in α-RuCl3 strongly competes with the crystallization of spin singlets into a valence bond solid. © 2018 authors. Published by the American Physical Society.

      @ARTICLE{Bastien2018,
      author={Bastien, G. and Garbarino, G. and Yadav, R. and Martinez-Casado, F.J. and Beltrán Rodríguez, R. and Stahl, Q. and Kusch, M. and Limandri, S.P. and Ray, R. and Lampen-Kelley, P. and Mandrus, D.G. and Nagler, S.E. and Roslova, M. and Isaeva, A. and Doert, T. and Hozoi, L. and Wolter, A.U.B. and Büchner, B. and Geck, J. and Van Den Brink, J.},
      title={Pressure-induced dimerization and valence bond crystal formation in the Kitaev-Heisenberg magnet α-RuCl3},
      journal={Physical Review B},
      year={2018},
      volume={97},
      number={24},
      doi={10.1103/PhysRevB.97.241108},
      art_number={241108},
      note={cited By 42},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048701800&doi=10.1103%2fPhysRevB.97.241108&partnerID=40&md5=3acd9f0160e35f75e33170b9f61341c9},
      affiliation={Leibniz-Institut für Festkörper- und Werkstoffforschung (IFW) Dresden, Dresden, 01171, Germany; European Synchrotron Radiation Facility, Grenoble, 38043, France; Institut Laue-Langevin, Grenoble, 38042, France; Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC, Universidad de Zaragoza, Zaragoza, 50009, Spain; Institut für Festkörper- und Materialphysik, Technische Universität Dresden, Dresden, 01062, Germany; IFEG, CONICET, Ciudad Universitaria, Medina Allende s/n, Cordoba, 5000, Argentina; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, United States; Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Fakultät für Chemie und Lebensmittelchemie, Technische Universität Dresden, Dresden, 01062, Germany; Institut für Theoretische Physik, Technische Universität Dresden, Dresden, 01062, Germany; Department of Physics, Harvard University, Cambridge, MA 02138, United States},
      abstract={Magnetization and high-resolution x-ray diffraction measurements of the Kitaev-Heisenberg material α-RuCl3 reveal a pressure-induced crystallographic and magnetic phase transition at a hydrostatic pressure of p∼0.2 GPa. This structural transition into a triclinic phase is characterized by a very strong dimerization of the Ru-Ru bonds, accompanied by a collapse of the magnetic susceptibility. Ab initio quantum-chemistry calculations disclose a pressure-induced enhancement of the direct 4d-4d bonding on particular Ru-Ru links, causing a sharp increase of the antiferromagnetic exchange interactions. These combined experimental and computational data show that the Kitaev spin-liquid phase in α-RuCl3 strongly competes with the crystallization of spin singlets into a valence bond solid. © 2018 authors. Published by the American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Lattice dynamics and metastability of fcc metals in the hcp structure and the crucial role of spin-orbit coupling in platinum
    • S. Schönecker, X. Li, M. Richter, L. Vitos
    • Physical Review B 97, 224305 (2018)
    • DOI   Abstract  

      We investigate the lattice dynamical properties of Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au in the nonequilibrium hcp structure by means of density-functional simulations, wherein spin-orbit coupling (SOC) was considered for Ir, Pt, and Au. The determined dynamical properties reveal that all eight elements possess a metastable hcp phase at zero temperature and pressure. The hcp Ni, Cu, Rh, Pd, and Au previously observed in nanostructures support this finding. We make evident that the inclusion of SOC is mandatory for an accurate description of the phonon dispersion relations and dynamical stability of hcp Pt. The underlying sensitivity of the interatomic force constants is ascribed to a SOC-induced splitting of degenerate band states accompanied by a pronounced reduction of electronic density of states at the Fermi level. To give further insight into the importance of SOC in Pt, we (i) focus on phase stability and examine a lattice transformation related to optical phonons in the hcp phase and (ii) focus on the generalized stacking fault energy (GSFE) of the fcc phase pertinent to crystal plasticity. We show that the intrinsic stable and unstable fault energies of the GSFE scale as in other common fcc metals, provided that the spin-orbit interaction is taken into account. © 2018 American Physical Society.

      @ARTICLE{Schönecker2018,
      author={Schönecker, S. and Li, X. and Richter, M. and Vitos, L.},
      title={Lattice dynamics and metastability of fcc metals in the hcp structure and the crucial role of spin-orbit coupling in platinum},
      journal={Physical Review B},
      year={2018},
      volume={97},
      number={22},
      doi={10.1103/PhysRevB.97.224305},
      art_number={224305},
      note={cited By 8},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048722613&doi=10.1103%2fPhysRevB.97.224305&partnerID=40&md5=85db9849587c59c4bd4b5cbb3da188f0},
      affiliation={Applied Materials Physics, Department of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm, SE-10044, Sweden; IFW Dresden, Dresden Center for Computational Materials Science, Dresden, D-01069, Germany; Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Box 516, Uppsala, SE-75120, Sweden; Research Institute for Solid State Physics and Optics, Wigner Research Center for Physics, P.O. Box 49, Budapest, H-1525, Hungary},
      abstract={We investigate the lattice dynamical properties of Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au in the nonequilibrium hcp structure by means of density-functional simulations, wherein spin-orbit coupling (SOC) was considered for Ir, Pt, and Au. The determined dynamical properties reveal that all eight elements possess a metastable hcp phase at zero temperature and pressure. The hcp Ni, Cu, Rh, Pd, and Au previously observed in nanostructures support this finding. We make evident that the inclusion of SOC is mandatory for an accurate description of the phonon dispersion relations and dynamical stability of hcp Pt. The underlying sensitivity of the interatomic force constants is ascribed to a SOC-induced splitting of degenerate band states accompanied by a pronounced reduction of electronic density of states at the Fermi level. To give further insight into the importance of SOC in Pt, we (i) focus on phase stability and examine a lattice transformation related to optical phonons in the hcp phase and (ii) focus on the generalized stacking fault energy (GSFE) of the fcc phase pertinent to crystal plasticity. We show that the intrinsic stable and unstable fault energies of the GSFE scale as in other common fcc metals, provided that the spin-orbit interaction is taken into account. © 2018 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • A Dual-Stimuli-Responsive Sodium-Bromine Battery with Ultrahigh Energy Density
    • F. Wang, H. Yang, J. Zhang, P. Zhang, G. Wang, X. Zhuang, G. Cuniberti, X. Feng
    • Advanced Materials 30, 1800028 (2018)
    • DOI   Abstract  

      Stimuli-responsive energy storage devices have emerged for the fast-growing popularity of intelligent electronics. However, all previously reported stimuli-responsive energy storage devices have rather low energy densities (<250 Wh kg–1) and single stimuli-response, which seriously limit their application scopes in intelligent electronics. Herein, a dual-stimuli-responsive sodium-bromine (Na//Br2) battery featuring ultrahigh energy density, electrochromic effect, and fast thermal response is demonstrated. Remarkably, the fabricated Na//Br2 battery exhibits a large operating voltage of 3.3 V and an energy density up to 760 Wh kg−1, which outperforms those for the state-of-the-art stimuli-responsive electrochemical energy storage devices. This work offers a promising approach for designing multi-stimuli-responsive and high-energy rechargeable batteries without sacrificing the electrochemical performance. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

      @ARTICLE{Wang2018,
      author={Wang, F. and Yang, H. and Zhang, J. and Zhang, P. and Wang, G. and Zhuang, X. and Cuniberti, G. and Feng, X.},
      title={A Dual-Stimuli-Responsive Sodium-Bromine Battery with Ultrahigh Energy Density},
      journal={Advanced Materials},
      year={2018},
      volume={30},
      number={23},
      doi={10.1002/adma.201800028},
      art_number={1800028},
      note={cited By 35},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046107138&doi=10.1002%2fadma.201800028&partnerID=40&md5=abca260aaa2e14fba62098add75b4ab0},
      affiliation={Chair of Molecular Functional Materials, School of Science, Technische Universität Dresden, Mommsenstrasse 4, Dresden, 01069, Germany; Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, Dresden, 01062, Germany; Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; The State Key Laboratory of Metal Matrix Composites & Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai, 200240, China},
      abstract={Stimuli-responsive energy storage devices have emerged for the fast-growing popularity of intelligent electronics. However, all previously reported stimuli-responsive energy storage devices have rather low energy densities (<250 Wh kg–1) and single stimuli-response, which seriously limit their application scopes in intelligent electronics. Herein, a dual-stimuli-responsive sodium-bromine (Na//Br2) battery featuring ultrahigh energy density, electrochromic effect, and fast thermal response is demonstrated. Remarkably, the fabricated Na//Br2 battery exhibits a large operating voltage of 3.3 V and an energy density up to 760 Wh kg−1, which outperforms those for the state-of-the-art stimuli-responsive electrochemical energy storage devices. This work offers a promising approach for designing multi-stimuli-responsive and high-energy rechargeable batteries without sacrificing the electrochemical performance. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim},
      author_keywords={electrochromic; high energy density; multi-functions; sodium-bromine battery; thermal response},
      document_type={Article},
      source={Scopus},
      }

  • Projection and transfer operators in adaptive isogeometric analysis with hierarchical B-splines
    • P. Hennig, M. Ambati, L. De Lorenzis, M. Kästner
    • Computer Methods in Applied Mechanics and Engineering 334, 313-336 (2018)
    • DOI   Abstract  

      We present projection methods and transfer operations required for adaptive mesh refinement/coarsening in problems with internal variables. We extend the results of Hennig et al. 2016 on Bézier extraction of truncated hierarchical B-splines and its application to adaptive isogeometric analysis. It is shown that isogeometric analysis improves the performance of transfer operations as already the coarsest mesh represents the exact geometry and the hierarchical structure allows for quadrature free projection methods. We propose two different local least squares projection methods for field variables and compare them to existing global and semi-local versions. We discuss the application of two different transfer operators for internal variables. An alternative new operator inspired by superconvergent patch recovery is also proposed. The presented projection methods and transfer operations are tested in benchmark problems and applied to phase-field modelling of spinodal decomposition and brittle and ductile fracture. © 2018 Elsevier B.V.

      @ARTICLE{Hennig2018313,
      author={Hennig, P. and Ambati, M. and De Lorenzis, L. and Kästner, M.},
      title={Projection and transfer operators in adaptive isogeometric analysis with hierarchical B-splines},
      journal={Computer Methods in Applied Mechanics and Engineering},
      year={2018},
      volume={334},
      pages={313-336},
      doi={10.1016/j.cma.2018.01.017},
      note={cited By 21},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042377915&doi=10.1016%2fj.cma.2018.01.017&partnerID=40&md5=3cf0801e6785296a5aa4157f5f692010},
      affiliation={Institute of Solid Mechanics, TU Dresden, Dresden, 01062, Germany; Institute of Applied Mechanics, TU Braunschweig, Braunschweig, 38106, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={We present projection methods and transfer operations required for adaptive mesh refinement/coarsening in problems with internal variables. We extend the results of Hennig et al. 2016 on Bézier extraction of truncated hierarchical B-splines and its application to adaptive isogeometric analysis. It is shown that isogeometric analysis improves the performance of transfer operations as already the coarsest mesh represents the exact geometry and the hierarchical structure allows for quadrature free projection methods. We propose two different local least squares projection methods for field variables and compare them to existing global and semi-local versions. We discuss the application of two different transfer operators for internal variables. An alternative new operator inspired by superconvergent patch recovery is also proposed. The presented projection methods and transfer operations are tested in benchmark problems and applied to phase-field modelling of spinodal decomposition and brittle and ductile fracture. © 2018 Elsevier B.V.},
      author_keywords={Adaptivity; Coarsening; Isogeometric analysis; Phase-field modelling; Refinement; Truncated hierarchical B-splines},
      document_type={Article},
      source={Scopus},
      }

  • Nematic liquid crystals on curved surfaces: A thin film limit
    • I. Nitschke, M. Nestler, S. Praetorius, H. Löwen, A. Voigt
    • Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 474, 20170686 (2018)
    • DOI   Abstract  

      We consider a thin film limit of a Landau-de Gennes Q-tensor model. In the limiting process, we observe a continuous transition where the normal and tangential parts of the Q-tensor decouple and various intrinsic and extrinsic contributions emerge. The main properties of the thin film model, like uniaxiality and parameter phase space, are preserved in the limiting process. For the derived surface Landau-de Gennes model, we consider an L2-gradient flow. The resulting tensor-valued surface partial differential equation is numerically solved to demonstrate realizations of the tight coupling of elastic and bulk free energy with geometric properties. © 2018 The Author(s) Published by the Royal Society. All rights reserved.

      @ARTICLE{Nitschke2018,
      author={Nitschke, I. and Nestler, M. and Praetorius, S. and Löwen, H. and Voigt, A.},
      title={Nematic liquid crystals on curved surfaces: A thin film limit},
      journal={Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences},
      year={2018},
      volume={474},
      number={2214},
      doi={10.1098/rspa.2017.0686},
      art_number={20170686},
      note={cited By 6},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049627191&doi=10.1098%2frspa.2017.0686&partnerID=40&md5=ad2e9e482e326a0d6298c82ca461a2e7},
      affiliation={Institut für Wissenschaftliches Rechnen, Technische Universität Dresden, Dresden, 01062, Germany; Institut für Theoretische Physik II - Soft Matter, Heinrich-HeineUniversität Düsseldorf, Düsseldorf, 40225, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany},
      abstract={We consider a thin film limit of a Landau-de Gennes Q-tensor model. In the limiting process, we observe a continuous transition where the normal and tangential parts of the Q-tensor decouple and various intrinsic and extrinsic contributions emerge. The main properties of the thin film model, like uniaxiality and parameter phase space, are preserved in the limiting process. For the derived surface Landau-de Gennes model, we consider an L2-gradient flow. The resulting tensor-valued surface partial differential equation is numerically solved to demonstrate realizations of the tight coupling of elastic and bulk free energy with geometric properties. © 2018 The Author(s) Published by the Royal Society. All rights reserved.},
      author_keywords={Nematic liquid crystals; Surface equation; Thin film limit},
      document_type={Article},
      source={Scopus},
      }

  • Defects at grain boundaries: A coarse-grained, three-dimensional description by the amplitude expansion of the phase-field crystal model
    • M. Salvalaglio, R. Backofen, K. R. Elder, A. Voigt
    • Physical Review Materials 2, 053804 (2018)
    • DOI   Abstract  

      We address a three-dimensional, coarse-grained description of dislocation networks at grain boundaries between rotated crystals. The so-called amplitude expansion of the phase-field crystal model is exploited with the aid of finite element method calculations. This approach allows for the description of microscopic features, such as dislocations, while simultaneously being able to describe length scales that are orders of magnitude larger than the lattice spacing. Moreover, it allows for the direct description of extended defects by means of a scalar order parameter. The versatility of this framework is shown by considering both fcc and bcc lattice symmetries and different rotation axes. First, the specific case of planar, twist grain boundaries is illustrated. The details of the method are reported and the consistency of the results with literature is discussed. Then, the dislocation networks forming at the interface between a spherical, rotated crystal embedded in an unrotated crystalline structure, are shown. Although explicitly accounting for dislocations which lead to an anisotropic shrinkage of the rotated grain, the extension of the spherical grain boundary is found to decrease linearly over time in agreement with the classical theory of grain growth and recent atomistic investigations. It is shown that the results obtained for a system with bcc symmetry agree very well with existing results, validating the methodology. Furthermore, fully original results are shown for fcc lattice symmetry, revealing the generality of the reported observations. © 2018 American Physical Society.

      @ARTICLE{Salvalaglio2018,
      author={Salvalaglio, M. and Backofen, R. and Elder, K.R. and Voigt, A.},
      title={Defects at grain boundaries: A coarse-grained, three-dimensional description by the amplitude expansion of the phase-field crystal model},
      journal={Physical Review Materials},
      year={2018},
      volume={2},
      number={5},
      doi={10.1103/PhysRevMaterials.2.053804},
      art_number={053804},
      note={cited By 9},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059634904&doi=10.1103%2fPhysRevMaterials.2.053804&partnerID=40&md5=8f1c3533eb8f2d54a1f7577610d57601},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Department of Physics, Oakland University, Rochester, MI 48309, United States; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={We address a three-dimensional, coarse-grained description of dislocation networks at grain boundaries between rotated crystals. The so-called amplitude expansion of the phase-field crystal model is exploited with the aid of finite element method calculations. This approach allows for the description of microscopic features, such as dislocations, while simultaneously being able to describe length scales that are orders of magnitude larger than the lattice spacing. Moreover, it allows for the direct description of extended defects by means of a scalar order parameter. The versatility of this framework is shown by considering both fcc and bcc lattice symmetries and different rotation axes. First, the specific case of planar, twist grain boundaries is illustrated. The details of the method are reported and the consistency of the results with literature is discussed. Then, the dislocation networks forming at the interface between a spherical, rotated crystal embedded in an unrotated crystalline structure, are shown. Although explicitly accounting for dislocations which lead to an anisotropic shrinkage of the rotated grain, the extension of the spherical grain boundary is found to decrease linearly over time in agreement with the classical theory of grain growth and recent atomistic investigations. It is shown that the results obtained for a system with bcc symmetry agree very well with existing results, validating the methodology. Furthermore, fully original results are shown for fcc lattice symmetry, revealing the generality of the reported observations. © 2018 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Active crystals on a sphere
    • S. Praetorius, A. Voigt, R. Wittkowski, H. Löwen
    • Physical Review E 97, 052615 (2018)
    • DOI   Abstract  

      Two-dimensional crystals on curved manifolds exhibit nontrivial defect structures. Here we consider „active crystals“ on a sphere, which are composed of self-propelled colloidal particles. Our work is based on a phase-field-crystal-type model that involves a density and a polarization field on the sphere. Depending on the strength of the self-propulsion, three different types of crystals are found: a static crystal, a self-spinning „vortex-vortex“ crystal containing two vortical poles of the local velocity, and a self-translating „source-sink“ crystal with a source pole where crystallization occurs and a sink pole where the active crystal melts. These different crystalline states as well as their defects are studied theoretically here and can in principle be confirmed in experiments. © 2018 American Physical Society.

      @ARTICLE{Praetorius2018,
      author={Praetorius, S. and Voigt, A. and Wittkowski, R. and Löwen, H.},
      title={Active crystals on a sphere},
      journal={Physical Review E},
      year={2018},
      volume={97},
      number={5},
      doi={10.1103/PhysRevE.97.052615},
      art_number={052615},
      note={cited By 20},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047780948&doi=10.1103%2fPhysRevE.97.052615&partnerID=40&md5=0c6f195cfe8ea23c8198130b1ed0c7c7},
      affiliation={Institute for Scientific Computing, Technische Universität Dresden, Dresden, D-01062, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, D-01062, Germany; Center for Systems Biology Dresden (CSBD), Dresden, D-01307, Germany; Institut für Theoretische Physik, Westfälische Wilhelms-Universität Münster, Münster, D-48149, Germany; Center for Nonlinear Science (CeNoS), Westfälische Wilhelms-Universität Münster, Münster, D-48149, Germany; Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, D-40225, Germany},
      abstract={Two-dimensional crystals on curved manifolds exhibit nontrivial defect structures. Here we consider "active crystals" on a sphere, which are composed of self-propelled colloidal particles. Our work is based on a phase-field-crystal-type model that involves a density and a polarization field on the sphere. Depending on the strength of the self-propulsion, three different types of crystals are found: a static crystal, a self-spinning "vortex-vortex" crystal containing two vortical poles of the local velocity, and a self-translating "source-sink" crystal with a source pole where crystallization occurs and a sink pole where the active crystal melts. These different crystalline states as well as their defects are studied theoretically here and can in principle be confirmed in experiments. © 2018 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Insight into doping efficiency of organic semiconductors from the analysis of the density of states in n-doped
    • C. Gaul, S. Hutsch, M. Schwarze, K. S. Schellhammer, F. Bussolotti, S. Kera, G. Cuniberti, K. Leo, F. Ortmann
    • Nature Materials 17, 439-444 (2018)
    • DOI   Abstract  

      Doping plays a crucial role in semiconductor physics, with n-doping being controlled by the ionization energy of the impurity relative to the conduction band edge. In organic semiconductors, efficient doping is dominated by various effects that are currently not well understood. Here, we simulate and experimentally measure, with direct and inverse photoemission spectroscopy, the density of states and the Fermi level position of the prototypical materials C60 and zinc phthalocyanine n-doped with highly efficient benzimidazoline radicals (2-Cyc-DMBI). We study the role of doping-induced gap states, and, in particular, of the difference Δ 1 between the electron affinity of the undoped material and the ionization potential of its doped counterpart. We show that this parameter is critical for the generation of free carriers and influences the conductivity of the doped films. Tuning of Δ 1 may provide alternative strategies to optimize the electronic properties of organic semiconductors. © 2018 The Author(s).

      @ARTICLE{Gaul2018439,
      author={Gaul, C. and Hutsch, S. and Schwarze, M. and Schellhammer, K.S. and Bussolotti, F. and Kera, S. and Cuniberti, G. and Leo, K. and Ortmann, F.},
      title={Insight into doping efficiency of organic semiconductors from the analysis of the density of states in n-doped},
      journal={Nature Materials},
      year={2018},
      volume={17},
      number={5},
      pages={439-444},
      doi={10.1038/s41563-018-0030-8},
      note={cited By 46},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042545903&doi=10.1038%2fs41563-018-0030-8&partnerID=40&md5=edeeb14001c923ffbdac1dcd2f0c7f72},
      affiliation={Center for Advancing Electronics Dresden, Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany; Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP), Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany; Institute for Materials Science, Max Bergmann Center for Biomaterials, Technische Universität Dresden, Dresden, Germany; Institute for Molecular Science, Department of Photo-Molecular Science, Myodaiji, Okazaki, Japan; Institute of Materials Research and Engineering, Agency of Science, Technology and Research (A STAR), Singapore, Singapore},
      abstract={Doping plays a crucial role in semiconductor physics, with n-doping being controlled by the ionization energy of the impurity relative to the conduction band edge. In organic semiconductors, efficient doping is dominated by various effects that are currently not well understood. Here, we simulate and experimentally measure, with direct and inverse photoemission spectroscopy, the density of states and the Fermi level position of the prototypical materials C60 and zinc phthalocyanine n-doped with highly efficient benzimidazoline radicals (2-Cyc-DMBI). We study the role of doping-induced gap states, and, in particular, of the difference Δ 1 between the electron affinity of the undoped material and the ionization potential of its doped counterpart. We show that this parameter is critical for the generation of free carriers and influences the conductivity of the doped films. Tuning of Δ 1 may provide alternative strategies to optimize the electronic properties of organic semiconductors. © 2018 The Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Chirality-Dependent Electron Spin Filtering by Molecular Monolayers of Helicenes
    • M. Kettner, V. V. Maslyuk, D. Nürenberg, J. Seibel, R. Gutierrez, G. Cuniberti, K. -H. Ernst, H. Zacharias
    • Journal of Physical Chemistry Letters 9, 2025-2030 (2018)
    • DOI   Abstract  

      The interaction of low-energy photoelectrons with well-ordered monolayers of enantiopure helical heptahelicene molecules adsorbed on metal surfaces leads to a preferential transmission of one longitudinally polarized spin component, which is strongly coupled to the helical sense of the molecules. Heptahelicene, composed of only carbon and hydrogen atoms, exhibits only a single helical turn but shows excess in longitudinal spin polarization of about PZ = 6 to 8% after transmission of initially balanced left- and right-handed spin polarized electrons. Insight into the electronic structure, that is, the projected density of states, and the spin-dependent electron scattering in the helicene molecule is gained by using spin-resolved density functional theory calculations and a model Hamiltonian approach, respectively. Our results support the semiclassical picture of electronic transport along a helical pathway under the influence of spin-orbit coupling induced by the electrostatic molecular potential. © 2018 American Chemical Society.

      @ARTICLE{Kettner20182025,
      author={Kettner, M. and Maslyuk, V.V. and Nürenberg, D. and Seibel, J. and Gutierrez, R. and Cuniberti, G. and Ernst, K.-H. and Zacharias, H.},
      title={Chirality-Dependent Electron Spin Filtering by Molecular Monolayers of Helicenes},
      journal={Journal of Physical Chemistry Letters},
      year={2018},
      volume={9},
      number={8},
      pages={2025-2030},
      doi={10.1021/acs.jpclett.8b00208},
      note={cited By 55},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045762554&doi=10.1021%2facs.jpclett.8b00208&partnerID=40&md5=ce7d003a2ba807314e36f15b73532194},
      affiliation={Center for Soft Nanoscience, Physikalisches Institut, University of Münster, Münster, 48149, Germany; Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, 8600, Switzerland; Dresden Center for Computational Materials Science, Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Department of Chemistry, University of Zurich, Zürich, 8057, Switzerland},
      abstract={The interaction of low-energy photoelectrons with well-ordered monolayers of enantiopure helical heptahelicene molecules adsorbed on metal surfaces leads to a preferential transmission of one longitudinally polarized spin component, which is strongly coupled to the helical sense of the molecules. Heptahelicene, composed of only carbon and hydrogen atoms, exhibits only a single helical turn but shows excess in longitudinal spin polarization of about PZ = 6 to 8% after transmission of initially balanced left- and right-handed spin polarized electrons. Insight into the electronic structure, that is, the projected density of states, and the spin-dependent electron scattering in the helicene molecule is gained by using spin-resolved density functional theory calculations and a model Hamiltonian approach, respectively. Our results support the semiclassical picture of electronic transport along a helical pathway under the influence of spin-orbit coupling induced by the electrostatic molecular potential. © 2018 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Solid-state dewetting of single-crystal silicon on insulator: effect of annealing temperature and patch size
    • M. Abbarchi, M. Naffouti, M. Lodari, M. Salvalaglio, R. Backofen, T. Bottein, A. Voigt, T. David, J. -B. Claude, M. Bouabdellaoui, A. Benkouider, I. Fraj, L. Favre, A. Ronda, I. Berbezier, D. Grosso, M. Bollani
    • Microelectronic Engineering 190, 1-6 (2018)
    • DOI   Abstract  

      We address the solid state dewetting of ultra-thin and ultra-large patches of monocrystalline silicon on insulator. We show that the underlying instability of the thin Si film under annealing can be perfectly controlled to form monocrystalline, complex nanoarchitectures extending over several microns. These complex patterns are obtained guiding the dewetting fronts by etching ad-hoc patches prior to annealing. They can be reproduced over hundreds of repetitions extending over hundreds of microns. We discuss the effect of annealing temperature and patch size on the stability of the final result of dewetting showing that for simple patches (e.g. simple squares) the final outcome is stable and well reproducible at 720 °C and for ~ 1 μm square size. Finally, we demonstrate that introducing additional features within squared patches (e.g. a hole within a square) stabilises the dewetting dynamic providing perfectly reproducible complex nanoarchitectures of 5 μm size. © 2018 Elsevier B.V.

      @ARTICLE{Abbarchi20181,
      author={Abbarchi, M. and Naffouti, M. and Lodari, M. and Salvalaglio, M. and Backofen, R. and Bottein, T. and Voigt, A. and David, T. and Claude, J.-B. and Bouabdellaoui, M. and Benkouider, A. and Fraj, I. and Favre, L. and Ronda, A. and Berbezier, I. and Grosso, D. and Bollani, M.},
      title={Solid-state dewetting of single-crystal silicon on insulator: effect of annealing temperature and patch size},
      journal={Microelectronic Engineering},
      year={2018},
      volume={190},
      pages={1-6},
      doi={10.1016/j.mee.2018.01.002},
      note={cited By 4},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85039982935&doi=10.1016%2fj.mee.2018.01.002&partnerID=40&md5=5d02262dae4c013a0159ba8861787e12},
      affiliation={Aix Marseille Université CNRS Université de Toulon IM2NP UMR 7334, Marseille, 13397, France; Laboratoire de Micro-optoélectronique et Nanostructures Faculté des Sciences de Monastir Université de Monastir, Monastir, 5019, Tunisia; Istituto di Fotonica e Nanotecnologie Consiglio Nazionale delle Ricerche (IFN-CNR), L-NESS laboratory, via Anzani 42, Como, 22100, Italy; Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={We address the solid state dewetting of ultra-thin and ultra-large patches of monocrystalline silicon on insulator. We show that the underlying instability of the thin Si film under annealing can be perfectly controlled to form monocrystalline, complex nanoarchitectures extending over several microns. These complex patterns are obtained guiding the dewetting fronts by etching ad-hoc patches prior to annealing. They can be reproduced over hundreds of repetitions extending over hundreds of microns. We discuss the effect of annealing temperature and patch size on the stability of the final result of dewetting showing that for simple patches (e.g. simple squares) the final outcome is stable and well reproducible at 720 °C and for ~ 1 μm square size. Finally, we demonstrate that introducing additional features within squared patches (e.g. a hole within a square) stabilises the dewetting dynamic providing perfectly reproducible complex nanoarchitectures of 5 μm size. © 2018 Elsevier B.V.},
      author_keywords={Nano-patterning; Solid-state dewetting; Ultra-thin silicon on insulator},
      document_type={Article},
      source={Scopus},
      }

  • Bioinspired thermoresponsive nanoscaled coatings: Tailor-made polymer brushes with bioconjugated arginine-glycine-aspartic acid-peptides
    • U. König, E. Psarra, O. Guskova, E. Bittrich, K. -J. Eichhorn, M. Müller, P. B. Welzel, M. Stamm, P. Uhlmann
    • Biointerphases 13, 021002 (2018)
    • DOI   Abstract  

      The development of bioengineered surface coatings with stimuli-responsive properties is beneficial for a number of biomedical applications. Environmentally responsive and switchable polymer brush systems have a great potential to create such smart biointerfaces. This study focuses on the bioconjugation of cell-instructive peptides, containing the arginine-glycine-aspartic acid tripeptide sequence (RGD motif), onto well-defined polymer brush films. Herein, the highly tailored end-grafted homo polymer brushes are either composed of the polyelectrolyte poly(acrylic) acid (PAA), providing the reactive carboxyl functionalities, or of the temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm). Of particular interest is the preparation of grafted-to binary brushes using both polymers and their subsequent conversion to RGD-biofunctionalized PNIPAAm-PAA binary brushes by a carbodiimide conjugation method. The bioconjugation process of two linear RGD-peptides Gly-Arg-Gly-Asp-Ser and Gly-Arg-Gly-Asp-Ser-Pro-Lys and one cyclic RGD-peptide cyclo(Arg-Gly-Asp-D-Tyr-Lys) is comparatively investigated by complementary analysis methods. Both techniques, in situ attenuated total reflectance Fourier transform infrared spectroscopy measurements and the in situ spectroscopic ellipsometric analysis, describe changes of the brush surface properties due to biofunctionalization. Besides, the bound RGD-peptide amount is quantitatively evaluated by ellipsometry in comparison to high performance liquid chromatography analysis data. Additionally, molecular dynamic simulations of the RGD-peptides themselves allow a better understanding of the bioconjugation process depending on the peptide properties. The significant influence on the bioconjugation result can be derived, on the one hand, of the polymer brush composition, especially from the PNIPAAm content, and, on the other hand, of the peptide dimension and its reactivity. © 2018 Author(s).

      @ARTICLE{König2018,
      author={König, U. and Psarra, E. and Guskova, O. and Bittrich, E. and Eichhorn, K.-J. and Müller, M. and Welzel, P.B. and Stamm, M. and Uhlmann, P.},
      title={Bioinspired thermoresponsive nanoscaled coatings: Tailor-made polymer brushes with bioconjugated arginine-glycine-aspartic acid-peptides},
      journal={Biointerphases},
      year={2018},
      volume={13},
      number={2},
      doi={10.1116/1.5020129},
      art_number={021002},
      note={cited By 4},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047332792&doi=10.1116%2f1.5020129&partnerID=40&md5=8e2e7e0559c0fe0c3924fce79a7b2c77},
      affiliation={Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, 01069, Germany; Physical Chemistry of Polymeric Materials, Department of Chemistry, Faculty of Science, Technische Universität Dresden, Bergstrasse 66, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; Department of Chemistry, Hamilton Hall, University of Nebraska-Lincoln, 639 N 12th Street, Lincoln, NE 68588, United States},
      abstract={The development of bioengineered surface coatings with stimuli-responsive properties is beneficial for a number of biomedical applications. Environmentally responsive and switchable polymer brush systems have a great potential to create such smart biointerfaces. This study focuses on the bioconjugation of cell-instructive peptides, containing the arginine-glycine-aspartic acid tripeptide sequence (RGD motif), onto well-defined polymer brush films. Herein, the highly tailored end-grafted homo polymer brushes are either composed of the polyelectrolyte poly(acrylic) acid (PAA), providing the reactive carboxyl functionalities, or of the temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm). Of particular interest is the preparation of grafted-to binary brushes using both polymers and their subsequent conversion to RGD-biofunctionalized PNIPAAm-PAA binary brushes by a carbodiimide conjugation method. The bioconjugation process of two linear RGD-peptides Gly-Arg-Gly-Asp-Ser and Gly-Arg-Gly-Asp-Ser-Pro-Lys and one cyclic RGD-peptide cyclo(Arg-Gly-Asp-D-Tyr-Lys) is comparatively investigated by complementary analysis methods. Both techniques, in situ attenuated total reflectance Fourier transform infrared spectroscopy measurements and the in situ spectroscopic ellipsometric analysis, describe changes of the brush surface properties due to biofunctionalization. Besides, the bound RGD-peptide amount is quantitatively evaluated by ellipsometry in comparison to high performance liquid chromatography analysis data. Additionally, molecular dynamic simulations of the RGD-peptides themselves allow a better understanding of the bioconjugation process depending on the peptide properties. The significant influence on the bioconjugation result can be derived, on the one hand, of the polymer brush composition, especially from the PNIPAAm content, and, on the other hand, of the peptide dimension and its reactivity. © 2018 Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Effect of magnetic zigzag edges in graphene-like nanoribbons on the thermoelectric power factor
    • S. Krompiewski, G. Cuniberti
    • Acta Physica Polonica A 133, 535-537 (2018)
    • DOI   Abstract  

      This study shows that magnetic edge states of graphene-like nanoribbons enhance effectively the thermoelectric performance. This is due to the antiparallel alignment of magnetic moments on opposite zigzag edges and the confinement effect, which jointly lead to the appearance of a gap in the electronic energy spectrum. Consequently, the Seebeck coefficient as well as the thermoelectric power factor get strongly enhanced (with respect to other alignment cases) at room temperature and energies not far away from the charge neutrality point. Moreover the corresponding figure of merit (ZT) is also improved as a result of the reduced electronic thermal conductance. © 2018 Polish Academy of Sciences. All rights reserved.

      @ARTICLE{Krompiewski2018535,
      author={Krompiewski, S. and Cuniberti, G.},
      title={Effect of magnetic zigzag edges in graphene-like nanoribbons on the thermoelectric power factor},
      journal={Acta Physica Polonica A},
      year={2018},
      volume={133},
      number={3},
      pages={535-537},
      doi={10.12693/APhysPolA.133.535},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045139896&doi=10.12693%2fAPhysPolA.133.535&partnerID=40&md5=7e0ee619c5fb404449538840b3bcda65},
      affiliation={Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, Poznań, 60-179, Poland; Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={This study shows that magnetic edge states of graphene-like nanoribbons enhance effectively the thermoelectric performance. This is due to the antiparallel alignment of magnetic moments on opposite zigzag edges and the confinement effect, which jointly lead to the appearance of a gap in the electronic energy spectrum. Consequently, the Seebeck coefficient as well as the thermoelectric power factor get strongly enhanced (with respect to other alignment cases) at room temperature and energies not far away from the charge neutrality point. Moreover the corresponding figure of merit (ZT) is also improved as a result of the reduced electronic thermal conductance. © 2018 Polish Academy of Sciences. All rights reserved.},
      document_type={Conference Paper},
      source={Scopus},
      }

  • Unimolecular Logic Gate with Classical Input by Single Gold Atoms
    • D. Skidin, O. Faizy, J. Krüger, F. Eisenhut, A. Jancarik, K. -H. Nguyen, G. Cuniberti, A. Gourdon, F. Moresco, C. Joachim
    • ACS Nano 12, 1139-1145 (2018)
    • DOI   Abstract  

      By a combination of solution and on-surface chemistry, we synthesized an asymmetric starphene molecule with two long anthracenyl input branches and a short naphthyl output branch on the Au(111) surface. Starting from this molecule, we could demonstrate the working principle of a single molecule NAND logic gate by selectively contacting single gold atoms by atomic manipulation to the longer branches of the molecule. The logical input „1“ („0“) is defined by the interaction (noninteraction) of a gold atom with one of the input branches. The output is measured by scanning tunneling spectroscopy following the shift in energy of the electronic tunneling resonances at the end of the short branch of the molecule. © 2017 American Chemical Society.

      @ARTICLE{Skidin20181139,
      author={Skidin, D. and Faizy, O. and Krüger, J. and Eisenhut, F. and Jancarik, A. and Nguyen, K.-H. and Cuniberti, G. and Gourdon, A. and Moresco, F. and Joachim, C.},
      title={Unimolecular Logic Gate with Classical Input by Single Gold Atoms},
      journal={ACS Nano},
      year={2018},
      volume={12},
      number={2},
      pages={1139-1145},
      doi={10.1021/acsnano.7b06650},
      note={cited By 8},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042649463&doi=10.1021%2facsnano.7b06650&partnerID=40&md5=cb45de533af2bb049d0364b8f29b0390},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01069, Germany; GNS and MANA Satellite, CEMES, CNRS, 29 Rue J. Marvig, Toulouse, Cedex, 31055, France; Laboratoire de Physique Théorique, IRSAMC, Université de Toulouse, CNRS, UPS, Toulouse, Cedex, 31055, France; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01069, Germany; School of Nano Science, Institute for Research in Fundamental Sciences (IPM), Tehran, 19395-5531, Iran},
      abstract={By a combination of solution and on-surface chemistry, we synthesized an asymmetric starphene molecule with two long anthracenyl input branches and a short naphthyl output branch on the Au(111) surface. Starting from this molecule, we could demonstrate the working principle of a single molecule NAND logic gate by selectively contacting single gold atoms by atomic manipulation to the longer branches of the molecule. The logical input "1" ("0") is defined by the interaction (noninteraction) of a gold atom with one of the input branches. The output is measured by scanning tunneling spectroscopy following the shift in energy of the electronic tunneling resonances at the end of the short branch of the molecule. © 2017 American Chemical Society.},
      author_keywords={asymmetric starphene; molecular logic gate; on-surface synthesis; quantum Hamiltonian computing (QHC); scanning tunneling microscopy (STM)},
      document_type={Article},
      source={Scopus},
      }

  • DFT study of interaction of additives with Cu(111) surface relevant to Cu electrodeposition
    • A. Dianat, H. Yang, M. Bobeth, G. Cuniberti
    • Journal of Applied Electrochemistry 48, 211-219 (2018)
    • DOI   Abstract  

      Abstract: The interaction of additives and ions with the copper surface plays a crucial role in the copper electroplating process. In this work, the interaction of the additives polyethylene glycol (PEG) and bis(3-sulfopropyl)-disulfide (SPS) as well as of chloride with the Cu(111) surface is considered within the framework of density functional theory. In the presence of water, the adsorption energy of chloride diminishes by about 1 eV compared to the case in vacuum. The activation barrier for chloride desorption was found to be 0.8 eV. Simulations of the deposition of copper atoms on a Cl-covered copper surface revealed that Cl atoms are always displaced to the surface. Calculations of adsorption energies of additives in vacuum indicated that the accelerator molecule SPS is bound stronger to Cu(111) than the suppressor molecule PEG. A comparatively strong adsorption of additives was found on a copper surface covered with a Cl–Cu mixed layer. Investigation of the dynamics of additives on Cu(111) by means of first principles molecular dynamics revealed an occasional spontaneous decomposition of an SPS molecule into two MPS molecules. Graphical Abstract: [Figure not available: see fulltext.]. © 2018, Springer Science+Business Media B.V., part of Springer Nature.

      @ARTICLE{Dianat2018211,
      author={Dianat, A. and Yang, H. and Bobeth, M. and Cuniberti, G.},
      title={DFT study of interaction of additives with Cu(111) surface relevant to Cu electrodeposition},
      journal={Journal of Applied Electrochemistry},
      year={2018},
      volume={48},
      number={2},
      pages={211-219},
      doi={10.1007/s10800-018-1150-1},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040773817&doi=10.1007%2fs10800-018-1150-1&partnerID=40&md5=d255dd54ddfe53f1425a2616ee862c69},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Abstract: The interaction of additives and ions with the copper surface plays a crucial role in the copper electroplating process. In this work, the interaction of the additives polyethylene glycol (PEG) and bis(3-sulfopropyl)-disulfide (SPS) as well as of chloride with the Cu(111) surface is considered within the framework of density functional theory. In the presence of water, the adsorption energy of chloride diminishes by about 1 eV compared to the case in vacuum. The activation barrier for chloride desorption was found to be 0.8 eV. Simulations of the deposition of copper atoms on a Cl-covered copper surface revealed that Cl atoms are always displaced to the surface. Calculations of adsorption energies of additives in vacuum indicated that the accelerator molecule SPS is bound stronger to Cu(111) than the suppressor molecule PEG. A comparatively strong adsorption of additives was found on a copper surface covered with a Cl–Cu mixed layer. Investigation of the dynamics of additives on Cu(111) by means of first principles molecular dynamics revealed an occasional spontaneous decomposition of an SPS molecule into two MPS molecules. Graphical Abstract: [Figure not available: see fulltext.]. © 2018, Springer Science+Business Media B.V., part of Springer Nature.},
      author_keywords={Ab initio calculation; Additives; Adsorption energy; Copper electrodeposition; Damascene metallization},
      document_type={Article},
      source={Scopus},
      }

  • First-Principle-Based Phonon Transport Properties of Nanoscale Graphene Grain Boundaries
    • L. M. Sandonas, H. Sevinçli, R. Gutierrez, G. Cuniberti
    • Advanced Science 5, 1700365 (2018)
    • DOI   Abstract  

      The integrity of phonon transport properties of large graphene (linear and curved) grain boundaries (GBs) is investigated under the influence of structural and dynamical disorder. To do this, density functional tight-binding (DFTB) method is combined with atomistic Green’s function technique. The results show that curved GBs have lower thermal conductance than linear GBs. Its magnitude depends on the length of the curvature and out-of-plane structural distortions at the boundary, having stronger influence the latter one. Moreover, it is found that by increasing the defects at the boundary, the transport properties can strongly be reduced in comparison to the effect produced by heating up the boundary region. This is due to the large reduction of the phonon transmission for in-plane and out-of-plane vibrational modes after increasing the structural disorder in the GBs. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

      @ARTICLE{Sandonas2018,
      author={Sandonas, L.M. and Sevinçli, H. and Gutierrez, R. and Cuniberti, G.},
      title={First-Principle-Based Phonon Transport Properties of Nanoscale Graphene Grain Boundaries},
      journal={Advanced Science},
      year={2018},
      volume={5},
      number={2},
      doi={10.1002/advs.201700365},
      art_number={1700365},
      note={cited By 14},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040521258&doi=10.1002%2fadvs.201700365&partnerID=40&md5=35f818b4334fccbc1e2e51683255e9b7},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany; Department of Materials Science and Engineering, Izmir Institute of Technology, Izmir, Urla, 35430, Turkey; ICTP-ECAR Eurasian Centre for Advanced Research, Izmir Institute of Technology, Izmir, Urla, 35430, Turkey; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={The integrity of phonon transport properties of large graphene (linear and curved) grain boundaries (GBs) is investigated under the influence of structural and dynamical disorder. To do this, density functional tight-binding (DFTB) method is combined with atomistic Green's function technique. The results show that curved GBs have lower thermal conductance than linear GBs. Its magnitude depends on the length of the curvature and out-of-plane structural distortions at the boundary, having stronger influence the latter one. Moreover, it is found that by increasing the defects at the boundary, the transport properties can strongly be reduced in comparison to the effect produced by heating up the boundary region. This is due to the large reduction of the phonon transmission for in-plane and out-of-plane vibrational modes after increasing the structural disorder in the GBs. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim},
      author_keywords={DFTB calculations; grain boundaries; graphene; Landauer theory; phonon transport},
      document_type={Article},
      source={Scopus},
      }

  • Photosensitive Cationic Azobenzene Surfactants: Thermodynamics of Hydration and the Complex Formation with Poly(methacrylic acid)
    • M. Montagna, O. Guskova
    • Langmuir 34, 311-321 (2018)
    • DOI   Abstract  

      In this computational work, we investigate the photosensitive cationic surfactants with the trimethylammonium or polyamine hydrophilic head and the azobenzene-containing hydrophobic tail. The azobenzene-based molecules are known to undergo a reversible trans-cis-trans isomerization reaction when subjected to UV-visible light irradiation. Combining the density functional theory and the all-atom molecular dynamics simulations, the structural and the hydration properties of the trans- and the cis-isomers and their interaction with the oppositely charged poly(methacrylic acid) in aqueous solution are investigated. We establish and quantify the correlations of the molecular structure and the isomerization state of the surfactants and their hydrophilicity/hydrophobicity and the self-assembling altered by light. For this reason, we compare the hydration free energies of the trans- and the cis-isomers. Moreover, the investigations of the interaction strength between the azobenzene molecules and the polyanion provide additional elucidations of the recent experimental and theoretical studies on the light triggered reversible deformation behavior of the microgels and the polymer brushes loaded with azobenzene surfactants. © 2017 American Chemical Society.

      @ARTICLE{Montagna2018311,
      author={Montagna, M. and Guskova, O.},
      title={Photosensitive Cationic Azobenzene Surfactants: Thermodynamics of Hydration and the Complex Formation with Poly(methacrylic acid)},
      journal={Langmuir},
      year={2018},
      volume={34},
      number={1},
      pages={311-321},
      doi={10.1021/acs.langmuir.7b03638},
      note={cited By 22},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85039037259&doi=10.1021%2facs.langmuir.7b03638&partnerID=40&md5=17c63f26a364a64b2afdeec64c452ae8},
      affiliation={Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, D-01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, D-01062, Germany},
      abstract={In this computational work, we investigate the photosensitive cationic surfactants with the trimethylammonium or polyamine hydrophilic head and the azobenzene-containing hydrophobic tail. The azobenzene-based molecules are known to undergo a reversible trans-cis-trans isomerization reaction when subjected to UV-visible light irradiation. Combining the density functional theory and the all-atom molecular dynamics simulations, the structural and the hydration properties of the trans- and the cis-isomers and their interaction with the oppositely charged poly(methacrylic acid) in aqueous solution are investigated. We establish and quantify the correlations of the molecular structure and the isomerization state of the surfactants and their hydrophilicity/hydrophobicity and the self-assembling altered by light. For this reason, we compare the hydration free energies of the trans- and the cis-isomers. Moreover, the investigations of the interaction strength between the azobenzene molecules and the polyanion provide additional elucidations of the recent experimental and theoretical studies on the light triggered reversible deformation behavior of the microgels and the polymer brushes loaded with azobenzene surfactants. © 2017 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Morphological evolution of Ge/Si nano-strips driven by Rayleigh-like instability
    • M. Salvalaglio, P. Zaumseil, Y. Yamamoto, O. Skibitzki, R. Bergamaschini, T. Schroeder, A. Voigt, G. Capellini
    • Applied Physics Letters 112, 022101 (2018)
    • DOI   Abstract  

      We present the morphological evolution obtained during the annealing of Ge strips grown on Si ridges as a prototypical process for 3D device architectures and nanophotonic applications. In particular, the morphological transition occurring from Ge/Si nanostrips to nanoislands is illustrated. The combined effect of performing annealing at different temperatures and varying the lateral size of the Si ridge underlying the Ge strips is addressed by means of a synergistic experimental and theoretical analysis. Indeed, three-dimensional phase-field simulations of surface diffusion, including the contributions of both surface and elastic energy, are exploited to understand the outcomes of annealing experiments. The breakup of Ge/Si strips, due to the activation of surface diffusion at high temperature, is found to be mainly driven by surface-energy reduction, thus pointing to a Rayleigh-like instability. The residual strain is found to play a minor role, only inducing local effects at the borders of the islands and an enhancement of the instability. © 2018 Author(s).

      @ARTICLE{Salvalaglio2018,
      author={Salvalaglio, M. and Zaumseil, P. and Yamamoto, Y. and Skibitzki, O. and Bergamaschini, R. and Schroeder, T. and Voigt, A. and Capellini, G.},
      title={Morphological evolution of Ge/Si nano-strips driven by Rayleigh-like instability},
      journal={Applied Physics Letters},
      year={2018},
      volume={112},
      number={2},
      doi={10.1063/1.5007937},
      art_number={022101},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040460434&doi=10.1063%2f1.5007937&partnerID=40&md5=b94142a49bee639a2491a29dd8366f39},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; IHP, Im Technologiepark 25, Frankfurt (Oder), 15236, Germany; Department of Materials Science, Università di Milano-Bicocca, Via R. Cozzi 55, Milano, I-20126, Italy; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Department of Sciences, Università Roma Tre, Viale Marconi 446, Roma, I-00146, Italy},
      abstract={We present the morphological evolution obtained during the annealing of Ge strips grown on Si ridges as a prototypical process for 3D device architectures and nanophotonic applications. In particular, the morphological transition occurring from Ge/Si nanostrips to nanoislands is illustrated. The combined effect of performing annealing at different temperatures and varying the lateral size of the Si ridge underlying the Ge strips is addressed by means of a synergistic experimental and theoretical analysis. Indeed, three-dimensional phase-field simulations of surface diffusion, including the contributions of both surface and elastic energy, are exploited to understand the outcomes of annealing experiments. The breakup of Ge/Si strips, due to the activation of surface diffusion at high temperature, is found to be mainly driven by surface-energy reduction, thus pointing to a Rayleigh-like instability. The residual strain is found to play a minor role, only inducing local effects at the borders of the islands and an enhancement of the instability. © 2018 Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Solving the incompressible surface Navier-Stokes equation by surface finite elements
    • S. Reuther, A. Voigt
    • Physics of Fluids 30, 012107 (2018)
    • DOI   Abstract  

      We consider a numerical approach for the incompressible surface Navier-Stokes equation on surfaces with arbitrary genus g(S). The approach is based on a reformulation of the equation in Cartesian coordinates of the embedding R3, penalization of the normal component, a Chorin projection method, and discretization in space by surface finite elements for each component. The approach thus requires only standard ingredients which most finite element implementations can offer. We compare computational results with discrete exterior calculus simulations on a torus and demonstrate the interplay of the flow field with the topology by showing realizations of the Poincaré-Hopf theorem on n-tori. © 2018 Author(s).

      @ARTICLE{Reuther2018,
      author={Reuther, S. and Voigt, A.},
      title={Solving the incompressible surface Navier-Stokes equation by surface finite elements},
      journal={Physics of Fluids},
      year={2018},
      volume={30},
      number={1},
      doi={10.1063/1.5005142},
      art_number={012107},
      note={cited By 29},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040778742&doi=10.1063%2f1.5005142&partnerID=40&md5=873d51ed9bd562655f60de7e4f52206a},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, Germany; Center for Systems Biology Dresden (CSBD), Dresden, Germany},
      abstract={We consider a numerical approach for the incompressible surface Navier-Stokes equation on surfaces with arbitrary genus g(S). The approach is based on a reformulation of the equation in Cartesian coordinates of the embedding R3, penalization of the normal component, a Chorin projection method, and discretization in space by surface finite elements for each component. The approach thus requires only standard ingredients which most finite element implementations can offer. We compare computational results with discrete exterior calculus simulations on a torus and demonstrate the interplay of the flow field with the topology by showing realizations of the Poincaré-Hopf theorem on n-tori. © 2018 Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Erratum: The interplay of curvature and vortices in flow on curved surfaces
    • S. Reuther, A. Voigt
    • Multiscale Modeling and Simulation 16, 1448-1453 (2018)
    • DOI   Abstract  

      We here correct the model and the derivation of the vorticity-stream function formulation for the incompressible surface Navier-Stokes equation on moving surfaces, proposed in [S. Reuther and A. Voigt, Multiscale Model. Simul., 13 (2015), pp. 632-643]. © 2018 Society for Industrial and Applied Mathematics.

      @ARTICLE{Reuther20181448,
      author={Reuther, S. and Voigt, A.},
      title={Erratum: The interplay of curvature and vortices in flow on curved surfaces},
      journal={Multiscale Modeling and Simulation},
      year={2018},
      volume={16},
      number={3},
      pages={1448-1453},
      doi={10.1137/18M1176464},
      note={cited By 2},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054254018&doi=10.1137%2f18M1176464&partnerID=40&md5=ee235164db559dec332be0a8f10dc1d5},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, Germany; Institute of Scientific Computing, Technische Universität Dresden, Dresden Center for Computational Materials Science (DCMS), Center for Systems Biology Dresden (CSBD), Dresden, Germany},
      abstract={We here correct the model and the derivation of the vorticity-stream function formulation for the incompressible surface Navier-Stokes equation on moving surfaces, proposed in [S. Reuther and A. Voigt, Multiscale Model. Simul., 13 (2015), pp. 632-643]. © 2018 Society for Industrial and Applied Mathematics.},
      author_keywords={Curved surfaces; Geometric force; Interface},
      document_type={Article},
      source={Scopus},
      }

  • Microscale finite element model of brittle multifilament yarn failure behavior
    • O. Döbrich, T. Gereke, M. Hengstermann, C. Cherif
    • Journal of Industrial Textiles 47, 870-882 (2018)
    • DOI   Abstract  

      A microscale model of multifilament reinforcement yarns made of technical carbon fibers is established based on the finite element method. The model is used to perform simulations of tensile failure. The failure behavior of dry multifilament carbon yarns is modeled using a maximum stress criterion with statistical distribution of the strength. The maximum stress is assigned to every single element and varied according to a normal distribution found in experimental tests of single filaments. The Weibull distribution is used for calculating the local failure stress. The material parameters are calculated in function of the element size to account for the volume-specific statistical breaking effect. Representative simulations of the tensile failure behavior prove the concept of the introduced assumptions. © 2016, © The Author(s) 2016.

      @ARTICLE{Döbrich2018870,
      author={Döbrich, O. and Gereke, T. and Hengstermann, M. and Cherif, C.},
      title={Microscale finite element model of brittle multifilament yarn failure behavior},
      journal={Journal of Industrial Textiles},
      year={2018},
      volume={47},
      number={5},
      pages={870-882},
      doi={10.1177/1528083716674908},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85038589632&doi=10.1177%2f1528083716674908&partnerID=40&md5=77a25924f793f8cb9d5bbc8c31cc7a50},
      affiliation={Institute of Textile Machinery and High Performance Material Technology, Faculty of Mechanical Science and Engineering, Technische Universität Dresden, Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, Germany},
      abstract={A microscale model of multifilament reinforcement yarns made of technical carbon fibers is established based on the finite element method. The model is used to perform simulations of tensile failure. The failure behavior of dry multifilament carbon yarns is modeled using a maximum stress criterion with statistical distribution of the strength. The maximum stress is assigned to every single element and varied according to a normal distribution found in experimental tests of single filaments. The Weibull distribution is used for calculating the local failure stress. The material parameters are calculated in function of the element size to account for the volume-specific statistical breaking effect. Representative simulations of the tensile failure behavior prove the concept of the introduced assumptions. © 2016, © The Author(s) 2016.},
      author_keywords={carbon fiber; failure; FEM; strength; Weibull; yarn},
      document_type={Article},
      source={Scopus},
      }

  • Copper electroplating with polyethylene glycol: Part II. Experimental analysis and determination of model parameters
    • H. Yang, R. Krause, C. Scheunert, R. Liske, B. Uhlig, A. Preusse, A. Dianat, M. Bobeth, G. Cuniberti
    • Journal of the Electrochemical Society 165, D13-D22 (2018)
    • DOI   Abstract  

      In the electrochemical deposition of copper on structured substrates, additives are commonly used as ingredients to refine the copper thin film properties. By means of cyclovoltametric (CV) measurements, we examine the process behavior of the additives PEG (polyethylene glycol) and chloride ions over a wide range of experimental parameters relevant for production-like conditions. In this plating process, additives practically are neither consumed in chemical reactions nor are they incorporated into the growing copper film. To understand the observed complex hysteresis behavior of the deposition current in CV scans, we have recently proposed a model which is able to qualitatively explain this behavior without supposing additive consumption. In the present study, we fit crucial parameters of this model from the experimental data to increase its predictive power. The quantitative agreement of performed simulations of CV scans with the measured scans demonstrates the validity of the proposed copper deposition model. Equipped with the determined parameter set, the model can help to optimize the copper plating process in industrial applications. © 2018 The Electrochemical Society.

      @ARTICLE{Yang2018D13,
      author={Yang, H. and Krause, R. and Scheunert, C. and Liske, R. and Uhlig, B. and Preusse, A. and Dianat, A. and Bobeth, M. and Cuniberti, G.},
      title={Copper electroplating with polyethylene glycol: Part II. Experimental analysis and determination of model parameters},
      journal={Journal of the Electrochemical Society},
      year={2018},
      volume={165},
      number={2},
      pages={D13-D22},
      doi={10.1149/2.0081802jes},
      note={cited By 6},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048421876&doi=10.1149%2f2.0081802jes&partnerID=40&md5=09acb202cb1cf1a2df474739b07807ed},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, Dresden, 01069, Germany; Fraunhofer Institute for Photonic Microsystems IPMS, Center Nanoelectronic Technologies, Dresden, 01099, Germany; Globalfoundries Dresden Module One LLC and Co. KG, Dresden, 01109, Germany; Dresden Center for Computational Materials Science (DCCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden (CfAED), Dresden, 01187, Germany},
      abstract={In the electrochemical deposition of copper on structured substrates, additives are commonly used as ingredients to refine the copper thin film properties. By means of cyclovoltametric (CV) measurements, we examine the process behavior of the additives PEG (polyethylene glycol) and chloride ions over a wide range of experimental parameters relevant for production-like conditions. In this plating process, additives practically are neither consumed in chemical reactions nor are they incorporated into the growing copper film. To understand the observed complex hysteresis behavior of the deposition current in CV scans, we have recently proposed a model which is able to qualitatively explain this behavior without supposing additive consumption. In the present study, we fit crucial parameters of this model from the experimental data to increase its predictive power. The quantitative agreement of performed simulations of CV scans with the measured scans demonstrates the validity of the proposed copper deposition model. Equipped with the determined parameter set, the model can help to optimize the copper plating process in industrial applications. © 2018 The Electrochemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Feasible Device Architectures for Ultrascaled CNTFETs
    • A. Pacheco-Sanchez, F. Fuchs, S. Mothes, A. Zienert, J. Schuster, S. Gemming, M. Claus
    • IEEE Transactions on Nanotechnology 17, 100-107 , 8113541 (2018)
    • DOI   Abstract  

      Feasible device architectures for ultrascaled carbon nanotubes field-effect transistors (CNTFETs) are studied down to 5.9 nm using a multiscale simulation approach covering electronic quantum transport simulations and numerical device simulations. Schottky-like and ohmiclike contacts are considered. The simplified approach employed in the numerical device simulator is critically evaluated and verified by means of comparing the results with electronic quantum simulation results of an identical device. Different performance indicators, such as the switching speed, switching energy, the subthreshold slope, Ion/Ioff-ratio, among others, are extracted for different device architectures. These values guide the evaluation of the technology for different application scenarios. For high-performance logic applications, the buried gate CNTFET is claimed to be the most suitable structure. © 2017 IEEE.

      @ARTICLE{Pacheco-Sanchez2018100,
      author={Pacheco-Sanchez, A. and Fuchs, F. and Mothes, S. and Zienert, A. and Schuster, J. and Gemming, S. and Claus, M.},
      title={Feasible Device Architectures for Ultrascaled CNTFETs},
      journal={IEEE Transactions on Nanotechnology},
      year={2018},
      volume={17},
      number={1},
      pages={100-107},
      doi={10.1109/TNANO.2017.2774605},
      art_number={8113541},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85035120535&doi=10.1109%2fTNANO.2017.2774605&partnerID=40&md5=d9e4fec18ddd6bcbb1b130a7adcf99bd},
      affiliation={Electron Devices and Integrated Circuits, Technische Universitat Dresden, Dresden, 01069, Germany; Center for Advancing Electronics Dresden, Technische Universitat Dresden, Dresden, 01069, Germany; Helmholtz-Zentrum Dresden-Rossendorf, Dresden, 01328, Germany; Fraunhofer Institute for Electronic Nano Systems, Chemnitz, 09126, Germany; Microtechnologies Chemnitz, University of Technology, Chemnitz, 09111, Germany; Dresden Center for Computational Materials Science, Technische Universitat Dresden, Dresden, 01069, Germany; Institute of Physics, Chemnitz University of Technology, Chemnitz, 09111, Germany},
      abstract={Feasible device architectures for ultrascaled carbon nanotubes field-effect transistors (CNTFETs) are studied down to 5.9 nm using a multiscale simulation approach covering electronic quantum transport simulations and numerical device simulations. Schottky-like and ohmiclike contacts are considered. The simplified approach employed in the numerical device simulator is critically evaluated and verified by means of comparing the results with electronic quantum simulation results of an identical device. Different performance indicators, such as the switching speed, switching energy, the subthreshold slope, Ion/Ioff-ratio, among others, are extracted for different device architectures. These values guide the evaluation of the technology for different application scenarios. For high-performance logic applications, the buried gate CNTFET is claimed to be the most suitable structure. © 2017 IEEE.},
      author_keywords={Atomistic simulation; Channel scaling; CNTFET; Electronic quantum simulation; Ion/Ioff-ratio; Multiscale modeling; Numerical device simulation; Subthreshold slope; Switching characteristics},
      document_type={Article},
      source={Scopus},
      }

2017

  • Molecular and Ionic Dipole Effects on the Electronic Properties of Si-/SiO2-Grafted Alkylamine Monolayers
    • A. Gankin, R. Sfez, E. Mervinetsky, J. Buchwald, A. Dianat, L. Medrano Sandonas, R. Gutierrez, G. Cuniberti, S. Yitzchaik
    • ACS Applied Materials and Interfaces 9, 44873-44879 (2017)
    • DOI   Abstract  

      In this work, we demonstrate the tunability of electronic properties of Si/SiO2 substrates by molecular and ionic surface modifications. The changes in the electronic properties such as the work function (WF) and electron affinity were experimentally measured by the contact potential difference technique and theoretically supported by density functional theory calculations. We attribute these molecular electronic effects mainly to the variations of molecular and surface dipoles of the ionic and neutral species. We have previously shown that for the alkylhalide monolayers, changing the tail group from Cl to I decreased the WF of the substrate. Here, we report on the opposite trend of WF changes, that is, the increase of the WF, obtained by using the anions of these halides from Cl- to I-. This trend was observed on self-assembled alkylammonium halide (-NH3+ X-, where X- = Cl-, Br-, or I-) monolayer-modified substrates. The monolayer’s formation was supported by ellipsometry measurements, X-ray photoelectron spectroscopy, and atomic force microscopy. Comparison of the theoretical and experimental data suggests that the ionic surface dipole depends mainly on the polarizability and the position of the counter halide anion along with the organization and packaging of the layer. The described ionic modification can be easily used for facile tailoring and design of the electronic properties Si/SiO2 substrates for various device applications. © 2017 American Chemical Society.

      @ARTICLE{Gankin201744873,
      author={Gankin, A. and Sfez, R. and Mervinetsky, E. and Buchwald, J. and Dianat, A. and Medrano Sandonas, L. and Gutierrez, R. and Cuniberti, G. and Yitzchaik, S.},
      title={Molecular and Ionic Dipole Effects on the Electronic Properties of Si-/SiO2-Grafted Alkylamine Monolayers},
      journal={ACS Applied Materials and Interfaces},
      year={2017},
      volume={9},
      number={51},
      pages={44873-44879},
      doi={10.1021/acsami.7b12218},
      note={cited By 6},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040042319&doi=10.1021%2facsami.7b12218&partnerID=40&md5=a6ca11cd98c94f1ca445a68f4b5f66d8},
      affiliation={Institute of Chemistry, Hebrew University of Jerusalem, Safra Campus, Givat Ram, Jerusalem, 91904, Israel; Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem, 91904, Israel; Department of Advanced Materials Engineering, Azrieli College of Engineering, Jerusalem, 9103501, Israel; Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany},
      abstract={In this work, we demonstrate the tunability of electronic properties of Si/SiO2 substrates by molecular and ionic surface modifications. The changes in the electronic properties such as the work function (WF) and electron affinity were experimentally measured by the contact potential difference technique and theoretically supported by density functional theory calculations. We attribute these molecular electronic effects mainly to the variations of molecular and surface dipoles of the ionic and neutral species. We have previously shown that for the alkylhalide monolayers, changing the tail group from Cl to I decreased the WF of the substrate. Here, we report on the opposite trend of WF changes, that is, the increase of the WF, obtained by using the anions of these halides from Cl- to I-. This trend was observed on self-assembled alkylammonium halide (-NH3+ X-, where X- = Cl-, Br-, or I-) monolayer-modified substrates. The monolayer's formation was supported by ellipsometry measurements, X-ray photoelectron spectroscopy, and atomic force microscopy. Comparison of the theoretical and experimental data suggests that the ionic surface dipole depends mainly on the polarizability and the position of the counter halide anion along with the organization and packaging of the layer. The described ionic modification can be easily used for facile tailoring and design of the electronic properties Si/SiO2 substrates for various device applications. © 2017 American Chemical Society.},
      author_keywords={contact potential difference; DFT; ionic dipole; molecular dipole; self-assembled monolayer; work function},
      document_type={Article},
      source={Scopus},
      }

  • On-Surface Annulation Reaction Cascade for the Selective Synthesis of Diindenopyrene
    • F. Eisenhut, T. Lehmann, A. Viertel, D. Skidin, J. Krüger, S. Nikipar, D. A. Ryndyk, C. Joachim, S. Hecht, F. Moresco, G. Cuniberti
    • ACS Nano 11, 12419-12425 (2017)
    • DOI   Abstract  

      We investigated the thermally induced on-surface cyclization of 4,10-bis(2′-bromo-4′-methylphenyl)-1,3-dimethylpyrene to form the previously unknown, nonalternant polyaromatic hydrocarbon diindeno[1,2,3-cd:1′,2′,3′-mn]pyrene on Au(111) using scanning tunneling microscopy and spectroscopy. The observed unimolecular reaction involves thermally induced debromination followed by selective ring closure to fuse the neighboring benzene moieties via a five-membered ring. The structure of the product has been verified experimentally as well as theoretically. Our results demonstrate that on-surface reactions give rise to unusual chemical reactivities and selectivities and provide access to nonalternant polyaromatic molecules. © 2017 American Chemical Society.

      @ARTICLE{Eisenhut201712419,
      author={Eisenhut, F. and Lehmann, T. and Viertel, A. and Skidin, D. and Krüger, J. and Nikipar, S. and Ryndyk, D.A. and Joachim, C. and Hecht, S. and Moresco, F. and Cuniberti, G.},
      title={On-Surface Annulation Reaction Cascade for the Selective Synthesis of Diindenopyrene},
      journal={ACS Nano},
      year={2017},
      volume={11},
      number={12},
      pages={12419-12425},
      doi={10.1021/acsnano.7b06459},
      note={cited By 10},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040080951&doi=10.1021%2facsnano.7b06459&partnerID=40&md5=afac22918a65c6ac7af75dcdf3c490ec},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01069, Germany; Department of Chemistry and IRIS Adlershof, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, Berlin, 12489, Germany; Bremen Center for Computational Materials Science, Universität Bremen, Bremen, 28359, Germany; GNS and MANA Satellite, CEMES, CNRS, 29 rue J. Marvig, Cedex Toulouse, 31055, France; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01069, Germany},
      abstract={We investigated the thermally induced on-surface cyclization of 4,10-bis(2′-bromo-4′-methylphenyl)-1,3-dimethylpyrene to form the previously unknown, nonalternant polyaromatic hydrocarbon diindeno[1,2,3-cd:1′,2′,3′-mn]pyrene on Au(111) using scanning tunneling microscopy and spectroscopy. The observed unimolecular reaction involves thermally induced debromination followed by selective ring closure to fuse the neighboring benzene moieties via a five-membered ring. The structure of the product has been verified experimentally as well as theoretically. Our results demonstrate that on-surface reactions give rise to unusual chemical reactivities and selectivities and provide access to nonalternant polyaromatic molecules. © 2017 American Chemical Society.},
      author_keywords={density functional theory; nonalternant polyaromatic hydrocarbons; on-surface reaction; reaction mechanism; scanning tunneling microscopy; single-molecule chemistry},
      document_type={Article},
      source={Scopus},
      }

  • Modeling and Simulation of Electrochemical Cells under Applied Voltage
    • M. Rossi, T. Wallmersperger, S. Neukamm, K. Padberg-Gehle
    • Electrochimica Acta 258, 241-254 (2017)
    • DOI   Abstract  

      The behavior of an electrochemical thin film under input voltage (potentiostatic) conditions is numerically investigated. Thin films are used in micro-batteries and proton-exchange-membrane fuel cells: these devices are expected to play a significant role in the next generation energy systems for use in vehicles as a replacement to combustion engines. The electrochemical investigation of thin films is a relevant topic for a wide range of applications such as hydrogels, ionic polymer metal composites, biological membranes, and treatment of tumors. In this work, a continuum-based model is presented in order to describe the behavior of thin membranes. The electrochemical behavior of thin membranes is usually hard to investigate with experiments. Therefore, numerical simulations are carried out in order to enable a better understanding of the chemical reactions occurring within microscopic regions at the electrode/electrolyte interfaces. Diffusive-migrative ionic fluxes and electric field distribution are considered. A one-dimensional domain is employed. The fully-coupled electrochemical field is given by the Poisson-Nernst-Planck equations. The model involves initial and interface/boundary conditions appropriate for an electrolytic/galvanic cell. The latter are the Stern layer conditions for polarization (or diffuse charge) effects and the Frumkin-Butler-Volmer equations for electrochemical kinetics of chemical reactions. Time-dependent numerical simulations within a finite element framework are performed using the commercial tools MATLAB and COMSOL Multiphysics. The results are consistent with the physical behavior of electrolytic cells under potentiostatic conditions. The time evolution of the main electrochemical parameters is in accordance with the imposed boundary/interface conditions. Interestingly, the ion flux and the electric field show slight asymmetries at the boundaries. Moreover, the model well predicts the behavior of systems, such as redox flow cells or rechargeable batteries, that can either run under applied voltage or applied current conditions. In fact, the field equations and the boundary conditions, presented here for electrolytic cells under applied voltage, can be applied also for galvanic cells under applied current. Equations and boundary conditions for applied voltage and applied current working conditions are presented in a compact form in order to emphasize differences and similarities. © 2017 Elsevier Ltd

      @ARTICLE{Rossi2017241,
      author={Rossi, M. and Wallmersperger, T. and Neukamm, S. and Padberg-Gehle, K.},
      title={Modeling and Simulation of Electrochemical Cells under Applied Voltage},
      journal={Electrochimica Acta},
      year={2017},
      volume={258},
      pages={241-254},
      doi={10.1016/j.electacta.2017.10.047},
      note={cited By 10},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032799273&doi=10.1016%2fj.electacta.2017.10.047&partnerID=40&md5=7fd7b94036c8b6afb7a9a0a3f2d48dfb},
      affiliation={Institute of Solid Mechanics, Technische Universität Dresden, 01062 Dresden, Germany; Institute of Scientific Computing, Technische Universität Dresden, 01062 Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, 01062 Dresden, Germany; Institute of Mathematics and its Didactics, Leuphana Universität Lüneburg, 21335 Lüneburg, Germany},
      abstract={The behavior of an electrochemical thin film under input voltage (potentiostatic) conditions is numerically investigated. Thin films are used in micro-batteries and proton-exchange-membrane fuel cells: these devices are expected to play a significant role in the next generation energy systems for use in vehicles as a replacement to combustion engines. The electrochemical investigation of thin films is a relevant topic for a wide range of applications such as hydrogels, ionic polymer metal composites, biological membranes, and treatment of tumors. In this work, a continuum-based model is presented in order to describe the behavior of thin membranes. The electrochemical behavior of thin membranes is usually hard to investigate with experiments. Therefore, numerical simulations are carried out in order to enable a better understanding of the chemical reactions occurring within microscopic regions at the electrode/electrolyte interfaces. Diffusive-migrative ionic fluxes and electric field distribution are considered. A one-dimensional domain is employed. The fully-coupled electrochemical field is given by the Poisson-Nernst-Planck equations. The model involves initial and interface/boundary conditions appropriate for an electrolytic/galvanic cell. The latter are the Stern layer conditions for polarization (or diffuse charge) effects and the Frumkin-Butler-Volmer equations for electrochemical kinetics of chemical reactions. Time-dependent numerical simulations within a finite element framework are performed using the commercial tools MATLAB and COMSOL Multiphysics. The results are consistent with the physical behavior of electrolytic cells under potentiostatic conditions. The time evolution of the main electrochemical parameters is in accordance with the imposed boundary/interface conditions. Interestingly, the ion flux and the electric field show slight asymmetries at the boundaries. Moreover, the model well predicts the behavior of systems, such as redox flow cells or rechargeable batteries, that can either run under applied voltage or applied current conditions. In fact, the field equations and the boundary conditions, presented here for electrolytic cells under applied voltage, can be applied also for galvanic cells under applied current. Equations and boundary conditions for applied voltage and applied current working conditions are presented in a compact form in order to emphasize differences and similarities. © 2017 Elsevier Ltd},
      author_keywords={Electrochemical cell; Finite elements; multi-field model; Stern layer; transport theory},
      document_type={Article},
      source={Scopus},
      }

  • Curvature controlled defect dynamics in topological active nematics
    • F. Alaimo, C. Köhler, A. Voigt
    • Scientific Reports 7, 5211 (2017)
    • DOI   Abstract  

      We study the spatiotemporal patterns that emerge when an active nematic film is topologically constraint. These topological constraints allow to control the non-equilibrium dynamics of the active system. We consider ellipsoidal shapes for which the resulting defects are 1/2 disclinations and analyze the relation between their location and dynamics and local geometric properties of the ellipsoid. We highlight two dynamic modes: A tunable periodic state that oscillates between two defect configurations on a spherical shape and a tunable rotating state for oblate spheroids. We further demonstrate the relation between defects and high Gaussian curvature and umbilical points and point out limits for a coarse-grained description of defects as self-propelled particles. © 2017 The Author(s).

      @ARTICLE{Alaimo2017,
      author={Alaimo, F. and Köhler, C. and Voigt, A.},
      title={Curvature controlled defect dynamics in topological active nematics},
      journal={Scientific Reports},
      year={2017},
      volume={7},
      number={1},
      doi={10.1038/s41598-017-05612-6},
      art_number={5211},
      note={cited By 23},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85024106590&doi=10.1038%2fs41598-017-05612-6&partnerID=40&md5=37b31711aca5f558c9c469608099d7b3},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany; Center of Systems Biology Dresden (CSBD), Pfotenhauerstr. 108, Dresden, 01307, Germany},
      abstract={We study the spatiotemporal patterns that emerge when an active nematic film is topologically constraint. These topological constraints allow to control the non-equilibrium dynamics of the active system. We consider ellipsoidal shapes for which the resulting defects are 1/2 disclinations and analyze the relation between their location and dynamics and local geometric properties of the ellipsoid. We highlight two dynamic modes: A tunable periodic state that oscillates between two defect configurations on a spherical shape and a tunable rotating state for oblate spheroids. We further demonstrate the relation between defects and high Gaussian curvature and umbilical points and point out limits for a coarse-grained description of defects as self-propelled particles. © 2017 The Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Copper Induced Conformational Changes of Tripeptide Monolayer Based Impedimetric Biosensor
    • E. Mervinetsky, I. Alshanski, Y. Hamo, L. M. Sandonas, A. Dianat, J. Buchwald, R. Gutierrez, G. Cuniberti, M. Hurevich, S. Yitzchaik
    • Scientific Reports 7, 9498 (2017)
    • DOI   Abstract  

      Copper ions play a major role in biological processes. Abnormal Cu2+ ions concentrations are associated with various diseases, hence, can be used as diagnostic target. Monitoring copper ion is currently performed by non-portable, expensive and complicated to use equipment. We present a label free and a highly sensitive electrochemical ion-detecting biosensor based on a Gly-Gly-His tripeptide layer that chelate with Cu2+ ions. The proposed sensing mechanism is that the chelation results in conformational changes in the peptide that forms a denser insulating layer that prevents RedOx species transfer to the surface. This chelation event was monitored using various electrochemical methods and surface chemistry analysis and supported by theoretical calculations. We propose a highly sensitive ion-detection biosensor that can detect Cu2+ ions in the pM range with high SNR parameter. © 2017 The Author(s).

      @ARTICLE{Mervinetsky2017,
      author={Mervinetsky, E. and Alshanski, I. and Hamo, Y. and Sandonas, L.M. and Dianat, A. and Buchwald, J. and Gutierrez, R. and Cuniberti, G. and Hurevich, M. and Yitzchaik, S.},
      title={Copper Induced Conformational Changes of Tripeptide Monolayer Based Impedimetric Biosensor},
      journal={Scientific Reports},
      year={2017},
      volume={7},
      number={1},
      doi={10.1038/s41598-017-10288-z},
      art_number={9498},
      note={cited By 12},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028376304&doi=10.1038%2fs41598-017-10288-z&partnerID=40&md5=c1d5228067d5e7029e4d152c0bc32d56},
      affiliation={Institute of Chemistry, Hebrew University of Jerusalem, Safra Campus, Givat Ram, Jerusalem, 91904, Israel; Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem, 91904, Israel; Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01069, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Copper ions play a major role in biological processes. Abnormal Cu2+ ions concentrations are associated with various diseases, hence, can be used as diagnostic target. Monitoring copper ion is currently performed by non-portable, expensive and complicated to use equipment. We present a label free and a highly sensitive electrochemical ion-detecting biosensor based on a Gly-Gly-His tripeptide layer that chelate with Cu2+ ions. The proposed sensing mechanism is that the chelation results in conformational changes in the peptide that forms a denser insulating layer that prevents RedOx species transfer to the surface. This chelation event was monitored using various electrochemical methods and surface chemistry analysis and supported by theoretical calculations. We propose a highly sensitive ion-detection biosensor that can detect Cu2+ ions in the pM range with high SNR parameter. © 2017 The Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Graphene nanoribbons on gold: Understanding superlubricity and edge effects
    • L. Gigli, N. Manini, A. Benassi, E. Tosatti, A. Vanossi, R. Guerra
    • 2D Materials 4, 045003 (2017)
    • DOI   Abstract  

      We address the atomistic nature of the longitudinal static friction against sliding of graphene nanoribbons (GNRs) deposited on gold, a system whose structural and mechanical properties have been recently the subject of intense experimental investigation. By means of numerical simulations and modeling we show that the GNR interior is structurally lubric (’superlubric‘) so that the static friction is dominated by the front/tail regions of the GNR, where the residual uncompensated lateral forces arising from the interaction with the underneath gold surface opposes the free sliding. As a result of this edge pinning the static friction does not grow with the GNR length, but oscillates around a fairly constant mean value. These friction oscillations are explained in terms of the GNRAu( 111) lattice mismatch: at certain GNR lengths close to an integer number of the beat (or moiré) length there is good force compensation and superlubric sliding; whereas close to half odd-integer periods there is significant pinning of the edge with larger friction. These results make qualitative contact with recent state-of-the-art atomic force microscopy experiment, as well as with the sliding of other different incommensurate systems. © 2017 IOP Publishing Ltd.

      @ARTICLE{Gigli2017,
      author={Gigli, L. and Manini, N. and Benassi, A. and Tosatti, E. and Vanossi, A. and Guerra, R.},
      title={Graphene nanoribbons on gold: Understanding superlubricity and edge effects},
      journal={2D Materials},
      year={2017},
      volume={4},
      number={4},
      doi={10.1088/2053-1583/aa7fdf},
      art_number={045003},
      note={cited By 22},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030094140&doi=10.1088%2f2053-1583%2faa7fdf&partnerID=40&md5=4f0fcef81c86c546259efc69f0ea7fb7},
      affiliation={International School for Advanced Studies (SISSA), Via Bonomea 265, Trieste, 34136, Italy; Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, Milano, 20133, Italy; Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden Center for Computational Materials Science (DCCMS), TU Dresden, Dresden, 01062, Germany; Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, Trieste, 34151, Italy; CNR-IOM Democritos National Simulation Center, Via Bonomea 265, Trieste, 34136, Italy; Center for Complexity and Biosystems, University of Milan, Milan, 20133, Italy},
      abstract={We address the atomistic nature of the longitudinal static friction against sliding of graphene nanoribbons (GNRs) deposited on gold, a system whose structural and mechanical properties have been recently the subject of intense experimental investigation. By means of numerical simulations and modeling we show that the GNR interior is structurally lubric ('superlubric') so that the static friction is dominated by the front/tail regions of the GNR, where the residual uncompensated lateral forces arising from the interaction with the underneath gold surface opposes the free sliding. As a result of this edge pinning the static friction does not grow with the GNR length, but oscillates around a fairly constant mean value. These friction oscillations are explained in terms of the GNRAu( 111) lattice mismatch: at certain GNR lengths close to an integer number of the beat (or moiré) length there is good force compensation and superlubric sliding; whereas close to half odd-integer periods there is significant pinning of the edge with larger friction. These results make qualitative contact with recent state-of-the-art atomic force microscopy experiment, as well as with the sliding of other different incommensurate systems. © 2017 IOP Publishing Ltd.},
      author_keywords={Friction; Graphene; Modeling; Nanoribbon; Simulation; Superlubricity},
      document_type={Article},
      source={Scopus},
      }

  • Enhancement of thermal transport properties of asymmetric Graphene/hBN nanoribbon heterojunctions by substrate engineering
    • L. Medrano Sandonas, G. Cuba-Supanta, R. Gutierrez, A. Dianat, C. V. Landauro, G. Cuniberti
    • Carbon 124, 642-650 (2017)
    • DOI   Abstract  

      Two-dimensional heterostructures offer a new route to manipulate phonons at the nanoscale. By performing non-equilibrium molecular dynamics simulations we address the thermal transport properties of structurally asymmetric graphene/hBN nanoribbon heterojunctions deposited on several substrates: graphite, Si(100), SiC(0001), and SiO2. Our results show a reduction of the interface thermal resistance in coplanar G/hBN heterojunctions upon substrate deposition which is mainly related to the increment on the power spectrum overlap. This effect is more pronounced for deposition on Si(100) and SiO2 substrates, independently of the planar stacking order of the materials. Moreover, it has been found that the thermal rectification factor increases as a function of the degree of structural asymmetry for hBN-G nanoribbons, reaching values up to ∼24%, while it displays a minimum (∈[0.7,2.4]) for G-hBN nanoribbons. More importantly, these properties can also be tuned by varying the substrate temperature, e.g., thermal rectification of symmetric hBN-G nanoribbon is enhanced from 8.8% to 79% by reducing the temperature of Si(100) substrate. Our investigation yields new insights into the physical mechanisms governing heat transport in G/hBN heterojunctions, and thus opens potential new routes to the design of phononic devices. © 2017 Elsevier Ltd

      @ARTICLE{MedranoSandonas2017642,
      author={Medrano Sandonas, L. and Cuba-Supanta, G. and Gutierrez, R. and Dianat, A. and Landauro, C.V. and Cuniberti, G.},
      title={Enhancement of thermal transport properties of asymmetric Graphene/hBN nanoribbon heterojunctions by substrate engineering},
      journal={Carbon},
      year={2017},
      volume={124},
      pages={642-650},
      doi={10.1016/j.carbon.2017.09.025},
      note={cited By 16},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029426712&doi=10.1016%2fj.carbon.2017.09.025&partnerID=40&md5=4fb6cbb5da5eeb3f5920796c1bbcc4f0},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany; Faculty of Physical Sciences, National University of San Marcos, P.O. Box 14-0149, Lima, 14, Peru; Centro de Investigaciones Tecnológicas, Biomédicas y Medioambientales (CIBTM), Bella Vista, Callao, Peru; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Two-dimensional heterostructures offer a new route to manipulate phonons at the nanoscale. By performing non-equilibrium molecular dynamics simulations we address the thermal transport properties of structurally asymmetric graphene/hBN nanoribbon heterojunctions deposited on several substrates: graphite, Si(100), SiC(0001), and SiO2. Our results show a reduction of the interface thermal resistance in coplanar G/hBN heterojunctions upon substrate deposition which is mainly related to the increment on the power spectrum overlap. This effect is more pronounced for deposition on Si(100) and SiO2 substrates, independently of the planar stacking order of the materials. Moreover, it has been found that the thermal rectification factor increases as a function of the degree of structural asymmetry for hBN-G nanoribbons, reaching values up to ∼24%, while it displays a minimum (∈[0.7,2.4]) for G-hBN nanoribbons. More importantly, these properties can also be tuned by varying the substrate temperature, e.g., thermal rectification of symmetric hBN-G nanoribbon is enhanced from 8.8% to 79% by reducing the temperature of Si(100) substrate. Our investigation yields new insights into the physical mechanisms governing heat transport in G/hBN heterojunctions, and thus opens potential new routes to the design of phononic devices. © 2017 Elsevier Ltd},
      author_keywords={G/hBN heterojunctions; Molecular dynamics; Substrate engineering; Thermal transport},
      document_type={Article},
      source={Scopus},
      }

  • Edge magnetism impact on electrical conductance and thermoelectric properties of graphenelike nanoribbons
    • S. Krompiewski, G. Cuniberti
    • Physical Review B 96, 155447 (2017)
    • DOI   Abstract  

      Edge states in narrow quasi-two-dimensional nanostructures determine, to a large extent, their electric, thermoelectric, and magnetic properties. Nonmagnetic edge states may quite often lead to topological-insulator-type behavior. However, another scenario develops when the zigzag edges are magnetic and the time reversal symmetry is broken. In this work we report on the electronic band structure modifications, electrical conductance, and thermoelectric properties of narrow zigzag nanoribbons with spontaneously magnetized edges. Theoretical studies based on the Kane-Mele-Hubbard tight-binding model show that for silicene, germanene, and stanene both the Seebeck coefficient and the thermoelectric power factor are strongly enhanced for energies close to the charge neutrality point. A perpendicular gate voltage lifts the spin degeneracy of energy bands in the ground state with antiparallel magnetized zigzag edges and makes the electrical conductance significantly spin polarized. Simultaneously the gate voltage worsens the thermoelectric performance. Estimated room-temperature figures of merit for the aforementioned nanoribbons can exceed a value of 3 if phonon thermal conductances are adequately reduced. © 2017 American Physical Society.

      @ARTICLE{Krompiewski2017,
      author={Krompiewski, S. and Cuniberti, G.},
      title={Edge magnetism impact on electrical conductance and thermoelectric properties of graphenelike nanoribbons},
      journal={Physical Review B},
      year={2017},
      volume={96},
      number={15},
      doi={10.1103/PhysRevB.96.155447},
      art_number={155447},
      note={cited By 8},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85037698720&doi=10.1103%2fPhysRevB.96.155447&partnerID=40&md5=4798cacdeade46d810cda36f6387c5a8},
      affiliation={Institute of Molecular Physics, Polish Academy of Sciences, Poznań, 60-179, Poland; Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={Edge states in narrow quasi-two-dimensional nanostructures determine, to a large extent, their electric, thermoelectric, and magnetic properties. Nonmagnetic edge states may quite often lead to topological-insulator-type behavior. However, another scenario develops when the zigzag edges are magnetic and the time reversal symmetry is broken. In this work we report on the electronic band structure modifications, electrical conductance, and thermoelectric properties of narrow zigzag nanoribbons with spontaneously magnetized edges. Theoretical studies based on the Kane-Mele-Hubbard tight-binding model show that for silicene, germanene, and stanene both the Seebeck coefficient and the thermoelectric power factor are strongly enhanced for energies close to the charge neutrality point. A perpendicular gate voltage lifts the spin degeneracy of energy bands in the ground state with antiparallel magnetized zigzag edges and makes the electrical conductance significantly spin polarized. Simultaneously the gate voltage worsens the thermoelectric performance. Estimated room-temperature figures of merit for the aforementioned nanoribbons can exceed a value of 3 if phonon thermal conductances are adequately reduced. © 2017 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Light-Induced Contraction/Expansion of 1D Photoswitchable Metallopolymer Monitored at the Solid–Liquid Interface
    • M. E. Garah, E. Borré, A. Ciesielski, A. Dianat, R. Gutierrez, G. Cuniberti, S. Bellemin-Laponnaz, M. Mauro, P. Samorì
    • Small 13, 1701790 (2017)
    • DOI   Abstract  

      The use of a bottom-up approach to the fabrication of nanopatterned functional surfaces, which are capable to respond to external stimuli, is of great current interest. Herein, the preparation of light-responsive, linear supramolecular metallopolymers constituted by the ideally infinite repetition of a ditopic ligand bearing an azoaryl moiety and Co(II) coordination nodes is described. The supramolecular polymerization process is followed by optical spectroscopy in dimethylformamide solution. Noteworthy, a submolecularly resolved scanning tunneling microscopy (STM) study of the in situ reversible trans-to-cis photoisomerization of a photoswitchable metallopolymer that self-assembles into 2D crystalline patterns onto a highly oriented pyrolytic graphite surface is achieved for the first time. The STM analysis of the nanopatterned surfaces is corroborated by modeling the physisorbed species onto a graphene slab before and after irradiation by means of density functional theory calculation. Significantly, switching of the monolayers consisting of supramolecular Co(II) metallopolymer bearing trans-azoaryl units to a novel pattern based on cis isomers can be triggered by UV light and reversed back to the trans conformer by using visible light, thereby restoring the trans-based supramolecular 2D packing. These findings represent a step forward toward the design and preparation of photoresponsive “smart” surfaces organized with an atomic precision. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

      @ARTICLE{Garah2017,
      author={Garah, M.E. and Borré, E. and Ciesielski, A. and Dianat, A. and Gutierrez, R. and Cuniberti, G. and Bellemin-Laponnaz, S. and Mauro, M. and Samorì, P.},
      title={Light-Induced Contraction/Expansion of 1D Photoswitchable Metallopolymer Monitored at the Solid–Liquid Interface},
      journal={Small},
      year={2017},
      volume={13},
      number={40},
      doi={10.1002/smll.201701790},
      art_number={1701790},
      note={cited By 13},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032856657&doi=10.1002%2fsmll.201701790&partnerID=40&md5=6397339db04a2c9fd6ec63c09bf4da1a},
      affiliation={Université de Strasbourg, CNRS, Institut de Science et d'Ingénierie Supramoléculaires (ISIS), 8 Allée Gaspard Monge, Strasbourg, 67000, France; Département des Matériaux Organiques, Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, Strasbourg, 67034, France; Institute for Materials Science and Max Bergmann Center of Biomaterials, Dresden University of Technology, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, Dresden Center for Computational Materials Science, Dresden University of Technology, Dresden, 01062, Germany},
      abstract={The use of a bottom-up approach to the fabrication of nanopatterned functional surfaces, which are capable to respond to external stimuli, is of great current interest. Herein, the preparation of light-responsive, linear supramolecular metallopolymers constituted by the ideally infinite repetition of a ditopic ligand bearing an azoaryl moiety and Co(II) coordination nodes is described. The supramolecular polymerization process is followed by optical spectroscopy in dimethylformamide solution. Noteworthy, a submolecularly resolved scanning tunneling microscopy (STM) study of the in situ reversible trans-to-cis photoisomerization of a photoswitchable metallopolymer that self-assembles into 2D crystalline patterns onto a highly oriented pyrolytic graphite surface is achieved for the first time. The STM analysis of the nanopatterned surfaces is corroborated by modeling the physisorbed species onto a graphene slab before and after irradiation by means of density functional theory calculation. Significantly, switching of the monolayers consisting of supramolecular Co(II) metallopolymer bearing trans-azoaryl units to a novel pattern based on cis isomers can be triggered by UV light and reversed back to the trans conformer by using visible light, thereby restoring the trans-based supramolecular 2D packing. These findings represent a step forward toward the design and preparation of photoresponsive “smart” surfaces organized with an atomic precision. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim},
      author_keywords={density functional theory (DFT); functional surfaces; metallopolymers; photoswitches; scanning tunneling microscopy (STM)},
      document_type={Article},
      source={Scopus},
      }

  • A convergence study of phase-field models for brittle fracture
    • T. Linse, P. Hennig, M. Kästner, R. de Borst
    • Engineering Fracture Mechanics 184, 307-318 (2017)
    • DOI   Abstract  

      A crucial issue in phase-field models for brittle fracture is whether the functional that describes the distributed crack converges to the functional of the discrete crack when the internal length scale introduced in the distribution function goes to zero. Theoretical proofs exist for the original theory. However, for continuous media as well as for discretised media, significant errors have been reported in numerical solutions regarding the approximated crack surface, and hence for the dissipated energy. We show that for a practical setting, where the internal length scale and the spacing of the discretisation are small but finite, the observed discrepancy partially stems from the fact that numerical studies consider specimens of a finite length, and partially relates to the irreversibility introduced when casting the variational theory for brittle fracture in a damage-like format. While some form of irreversibility may be required in numerical implementations, the precise form significantly influences the accuracy and convergence towards the discrete crack. © 2017 Elsevier Ltd

      @ARTICLE{Linse2017307,
      author={Linse, T. and Hennig, P. and Kästner, M. and de Borst, R.},
      title={A convergence study of phase-field models for brittle fracture},
      journal={Engineering Fracture Mechanics},
      year={2017},
      volume={184},
      pages={307-318},
      doi={10.1016/j.engfracmech.2017.09.013},
      note={cited By 25},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029690030&doi=10.1016%2fj.engfracmech.2017.09.013&partnerID=40&md5=0b92abffde05f06c8f275650a50cebfc},
      affiliation={Technische Universität Dresden, Institute of Solid Mechanics, Chair of Computational and Experimental Solid Mechanics, Dresden, 01062, Germany; Technische Universität Dresden, Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany; University of Sheffield, Department of Civil and Structural Engineering, Mappin Street, Sir Frederick Mappin Building, Sheffield, S1 3JD, United Kingdom},
      abstract={A crucial issue in phase-field models for brittle fracture is whether the functional that describes the distributed crack converges to the functional of the discrete crack when the internal length scale introduced in the distribution function goes to zero. Theoretical proofs exist for the original theory. However, for continuous media as well as for discretised media, significant errors have been reported in numerical solutions regarding the approximated crack surface, and hence for the dissipated energy. We show that for a practical setting, where the internal length scale and the spacing of the discretisation are small but finite, the observed discrepancy partially stems from the fact that numerical studies consider specimens of a finite length, and partially relates to the irreversibility introduced when casting the variational theory for brittle fracture in a damage-like format. While some form of irreversibility may be required in numerical implementations, the precise form significantly influences the accuracy and convergence towards the discrete crack. © 2017 Elsevier Ltd},
      author_keywords={Damage; Fracture; Gamma convergence; Phase-field model},
      document_type={Article},
      source={Scopus},
      }

  • Chemical Gating of a Weak Topological Insulator: Bi14Rh3I9
    • M. P. Ghimire, M. Richter
    • Nano Letters 17, 6303-6308 (2017)
    • DOI   Abstract  

      The compound Bi14Rh3I9 has recently been suggested as a weak three-dimensional topological insulator on the basis of angle-resolved photoemission and scanning-tunneling experiments in combination with density functional (DF) electronic structure calculations. These methods unanimously support the topological character of the headline compound, but a compelling confirmation could only be obtained by dedicated transport experiments. The latter, however, are biased by an intrinsic n-doping of the material’s surface due to its polarity. Electronic reconstruction of the polar surface shifts the topological gap below the Fermi energy, which would also prevent any future device application. Here, we report the results of DF slab calculations for chemically gated and counter-doped surfaces of Bi14Rh3I9. We demonstrate that both methods can be used to compensate the surface polarity without closing the electronic gap. © 2017 American Chemical Society.

      @ARTICLE{Ghimire20176303,
      author={Ghimire, M.P. and Richter, M.},
      title={Chemical Gating of a Weak Topological Insulator: Bi14Rh3I9},
      journal={Nano Letters},
      year={2017},
      volume={17},
      number={10},
      pages={6303-6308},
      doi={10.1021/acs.nanolett.7b03001},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031293187&doi=10.1021%2facs.nanolett.7b03001&partnerID=40&md5=f3a812d2777031550e8b4697c43523c0},
      affiliation={Leibniz Institute for Solid State and Materials Research, IFW Dresden, Helmholtzstr. 20, Dresden, D-01069, Germany; Condensed Matter Physics Research Center (CMPRC), Butwal-11, Rupandehi, Nepal; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, D-01062, Germany},
      abstract={The compound Bi14Rh3I9 has recently been suggested as a weak three-dimensional topological insulator on the basis of angle-resolved photoemission and scanning-tunneling experiments in combination with density functional (DF) electronic structure calculations. These methods unanimously support the topological character of the headline compound, but a compelling confirmation could only be obtained by dedicated transport experiments. The latter, however, are biased by an intrinsic n-doping of the material's surface due to its polarity. Electronic reconstruction of the polar surface shifts the topological gap below the Fermi energy, which would also prevent any future device application. Here, we report the results of DF slab calculations for chemically gated and counter-doped surfaces of Bi14Rh3I9. We demonstrate that both methods can be used to compensate the surface polarity without closing the electronic gap. © 2017 American Chemical Society.},
      author_keywords={Bi14Rh3I9; chemical gating; density functional theory; doping; quantum spin Hall effect; topological insulators},
      document_type={Article},
      source={Scopus},
      }

  • Nearest-neighbor Kitaev exchange blocked by charge order in electron-doped α-RuCl3
    • A. Koitzsch, C. Habenicht, E. Müller, M. Knupfer, B. Büchner, S. Kretschmer, M. Richter, J. Van Den Brink, F. Börrnert, D. Nowak, A. Isaeva, T. Doert
    • Physical Review Materials 1, 052001 (2017)
    • DOI   Abstract  

      A quantum spin liquid might be realized in α-RuCl3, a honeycomb-lattice magnetic material with substantial spin-orbit coupling. Moreover, α-RuCl3 is a Mott insulator, which implies the possibility that novel exotic phases occur upon doping. Here, we study the electronic structure of this material when intercalated with potassium by photoemission spectroscopy, electron energy loss spectroscopy, and density functional theory calculations. We obtain a stable stoichiometry at K0.5RuCl3. This gives rise to a peculiar charge disproportionation into formally Ru2+ (4d6) and Ru3+ (4d5). Every Ru 4d5 site with one hole in the t2g shell is surrounded by nearest neighbors of 4d6 character, where the t2g level is full and magnetically inert. Thus, each type of Ru site forms a triangular lattice, and nearest-neighbor interactions of the original honeycomb are blocked. © 2017 American Physical Society.

      @ARTICLE{Koitzsch2017,
      author={Koitzsch, A. and Habenicht, C. and Müller, E. and Knupfer, M. and Büchner, B. and Kretschmer, S. and Richter, M. and Van Den Brink, J. and Börrnert, F. and Nowak, D. and Isaeva, A. and Doert, Th.},
      title={Nearest-neighbor Kitaev exchange blocked by charge order in electron-doped α-RuCl3},
      journal={Physical Review Materials},
      year={2017},
      volume={1},
      number={5},
      doi={10.1103/PhysRevMaterials.1.052001},
      art_number={052001},
      note={cited By 13},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053423904&doi=10.1103%2fPhysRevMaterials.1.052001&partnerID=40&md5=e8d28cf671787998bc75a94abf9bc4c5},
      affiliation={IFW-Dresden, Helmholtzstrasse 20, Dresden, D-01069, Germany; Helmholtz Zentrum Dresden Rossendorf, Postfach 51 01 19, Dresden, D-01314, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, D-01062, Germany; Materialwissenschaftliche Elektronenmikroskopie, Universität Ulm, Albert-Einstein-Allee 11, Ulm, D-89081, Germany; Technische Universität Dresden, Department of Chemistry and Food Chemistry, Dresden, D-01062, Germany},
      abstract={A quantum spin liquid might be realized in α-RuCl3, a honeycomb-lattice magnetic material with substantial spin-orbit coupling. Moreover, α-RuCl3 is a Mott insulator, which implies the possibility that novel exotic phases occur upon doping. Here, we study the electronic structure of this material when intercalated with potassium by photoemission spectroscopy, electron energy loss spectroscopy, and density functional theory calculations. We obtain a stable stoichiometry at K0.5RuCl3. This gives rise to a peculiar charge disproportionation into formally Ru2+ (4d6) and Ru3+ (4d5). Every Ru 4d5 site with one hole in the t2g shell is surrounded by nearest neighbors of 4d6 character, where the t2g level is full and magnetically inert. Thus, each type of Ru site forms a triangular lattice, and nearest-neighbor interactions of the original honeycomb are blocked. © 2017 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Electronic transport in metallic carbon nanotubes with mixed defects within the strong localization regime
    • F. Teichert, A. Zienert, J. Schuster, M. Schreiber
    • Computational Materials Science 138, 49-57 (2017)
    • DOI   Abstract  

      We study the electron transport in metallic carbon nanotubes (CNTs) with realistic defects of different types. We focus on large CNTs with many defects in the mesoscopic range. In a recent paper we demonstrated that the electronic transport in those defective CNTs is in the regime of strong localization. We verify by quantum transport simulations that the localization length of CNTs with defects of mixed types can be related to the localization lengths of CNTs with identical defects by taking the weighted harmonic average. Secondly, we show how to use this result to estimate the conductance of arbitrary defective CNTs, avoiding time consuming transport calculations. © 2017 Elsevier B.V.

      @ARTICLE{Teichert201749,
      author={Teichert, F. and Zienert, A. and Schuster, J. and Schreiber, M.},
      title={Electronic transport in metallic carbon nanotubes with mixed defects within the strong localization regime},
      journal={Computational Materials Science},
      year={2017},
      volume={138},
      pages={49-57},
      doi={10.1016/j.commatsci.2017.06.001},
      note={cited By 10},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021324136&doi=10.1016%2fj.commatsci.2017.06.001&partnerID=40&md5=dfdee3181c5ece78c70ed237256bf3d6},
      affiliation={Institute of Physics, Chemnitz University of Technology, Chemnitz, 09107, Germany; Center for Microtechnologies, Chemnitz University of Technology, Chemnitz, 09107, Germany; Fraunhofer Institute for Electronic Nano Systems (ENAS), Chemnitz, 09126, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={We study the electron transport in metallic carbon nanotubes (CNTs) with realistic defects of different types. We focus on large CNTs with many defects in the mesoscopic range. In a recent paper we demonstrated that the electronic transport in those defective CNTs is in the regime of strong localization. We verify by quantum transport simulations that the localization length of CNTs with defects of mixed types can be related to the localization lengths of CNTs with identical defects by taking the weighted harmonic average. Secondly, we show how to use this result to estimate the conductance of arbitrary defective CNTs, avoiding time consuming transport calculations. © 2017 Elsevier B.V.},
      author_keywords={Carbon nanotube (CNT); Defect; Density-functional-based tight binding (DFTB); Electronic transport; Recursive Green's function formalism (RGF); Strong localization},
      document_type={Article},
      source={Scopus},
      }

  • Photoisomers of Azobenzene Star with a Flat Core: Theoretical Insights into Multiple States from DFT and MD Perspective
    • M. Koch, M. Saphiannikova, S. Santer, O. Guskova
    • Journal of Physical Chemistry B 121, 8854-8867 (2017)
    • DOI   Abstract  

      This study focuses on comparing physical properties of photoisomers of an azobenzene star with benzene-1,3,5-Tricarboxamide core. Three azobenzene arms of the molecule undergo a reversible trans-cis isomerization upon UV-vis light illumination giving rise to multiple states from the planar all-Trans one, via two mixed states to the kinked all-cis isomer. Employing density functional theory, we characterize the structural and photophysical properties of each state indicating a role the planar core plays in the coupling between azobenzene chromophores. To characterize the light-Triggered switching of solvophilicity/solvophobicity of the star, the difference in solvation free energy is calculated for the transfer of an azobenzene star from its gas phase to implicit or explicit solvents. For the latter case, classical all-Atom molecular dynamics simulations of aqueous solutions of azobenzene star are performed employing the polymer consistent force field to shed light on the thermodynamics of explicit hydration as a function of the isomerization state and on the structuring of water around the star. From the analysis of two contributions to the free energy of hydration, the nonpolar van der Waals and the electrostatic terms, it is concluded that isomerization specificity largely determines the polarity of the molecule and the solute-solvent electrostatic interactions. This convertible hydrophilicity/hydrophobicity together with readjustable occupied volume and the surface area accessible to water, affects the self-Assembly/disassembly of the azobenzene star with a flat core triggered by light. © 2017 American Chemical Society.

      @ARTICLE{Koch20178854,
      author={Koch, M. and Saphiannikova, M. and Santer, S. and Guskova, O.},
      title={Photoisomers of Azobenzene Star with a Flat Core: Theoretical Insights into Multiple States from DFT and MD Perspective},
      journal={Journal of Physical Chemistry B},
      year={2017},
      volume={121},
      number={37},
      pages={8854-8867},
      doi={10.1021/acs.jpcb.7b07350},
      note={cited By 8},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029741069&doi=10.1021%2facs.jpcb.7b07350&partnerID=40&md5=3ebed0c905f4e70bfd6836a711954e9d},
      affiliation={Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, 01069, Germany; Institute of Theoretical Physics, Technische Universität Dresden, Zellescher Weg 17, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01069, Germany; Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, Potsdam, 14476, Germany},
      abstract={This study focuses on comparing physical properties of photoisomers of an azobenzene star with benzene-1,3,5-Tricarboxamide core. Three azobenzene arms of the molecule undergo a reversible trans-cis isomerization upon UV-vis light illumination giving rise to multiple states from the planar all-Trans one, via two mixed states to the kinked all-cis isomer. Employing density functional theory, we characterize the structural and photophysical properties of each state indicating a role the planar core plays in the coupling between azobenzene chromophores. To characterize the light-Triggered switching of solvophilicity/solvophobicity of the star, the difference in solvation free energy is calculated for the transfer of an azobenzene star from its gas phase to implicit or explicit solvents. For the latter case, classical all-Atom molecular dynamics simulations of aqueous solutions of azobenzene star are performed employing the polymer consistent force field to shed light on the thermodynamics of explicit hydration as a function of the isomerization state and on the structuring of water around the star. From the analysis of two contributions to the free energy of hydration, the nonpolar van der Waals and the electrostatic terms, it is concluded that isomerization specificity largely determines the polarity of the molecule and the solute-solvent electrostatic interactions. This convertible hydrophilicity/hydrophobicity together with readjustable occupied volume and the surface area accessible to water, affects the self-Assembly/disassembly of the azobenzene star with a flat core triggered by light. © 2017 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Molecular Self-Assembly Driven by On-Surface Reduction: Anthracene and Tetracene on Au(111)
    • J. Krüger, F. Eisenhut, T. Lehmann, J. M. Alonso, J. Meyer, D. Skidin, R. Ohmann, D. A. Ryndyk, D. Pérez, E. Guitián, D. Peña, F. Moresco, G. Cuniberti
    • Journal of Physical Chemistry C 121, 20353-20358 (2017)
    • DOI   Abstract  

      Epoxyacenes adsorbed on metal surfaces form acenes during thermally induced reduction in ultrahigh vacuum conditions. The incorporation of oxygen bridges into a hydrocarbon backbone leads to an enhanced stability of these molecular precursors under ambient condition; however, it has also a distinct influence on their adsorption and self-Assembly on metal surfaces. Here, a low-Temperature scanning tunneling microscopy (LT-STM) study of two different epoxyacenes on the Au(111) surface at submonolayer coverage is presented. Both molecules show self-Assembly based on hydrogen bonding. While for the molecules with a single epoxy moiety nanostructures of three molecules are formed, extended molecular networks are achieved with two epoxy moieties and a slightly higher surface coverage. Upon annealing at 390 K, the molecules are reduced to the respective acene; however, both systems keep a similar assembled structure. The experimental STM images supported by theoretical calculations show that the self-Assembly of the on-surface fabricated acenes is greatly influenced by the on-surface reaction and strongly differs from the adsorption pattern of directly deposited acenes, highlighting the importance of the cleaved oxygen in the self-Assembly. © 2017 American Chemical Society.

      @ARTICLE{Krüger201720353,
      author={Krüger, J. and Eisenhut, F. and Lehmann, T. and Alonso, J.M. and Meyer, J. and Skidin, D. and Ohmann, R. and Ryndyk, D.A. and Pérez, D. and Guitián, E. and Peña, D. and Moresco, F. and Cuniberti, G.},
      title={Molecular Self-Assembly Driven by On-Surface Reduction: Anthracene and Tetracene on Au(111)},
      journal={Journal of Physical Chemistry C},
      year={2017},
      volume={121},
      number={37},
      pages={20353-20358},
      doi={10.1021/acs.jpcc.7b06131},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029744901&doi=10.1021%2facs.jpcc.7b06131&partnerID=40&md5=d41ece6e38659c9896e16655a165e3bd},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials and Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01069, Germany; Centro de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, Santiago de Compostela, 15782, Spain; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01069, Germany},
      abstract={Epoxyacenes adsorbed on metal surfaces form acenes during thermally induced reduction in ultrahigh vacuum conditions. The incorporation of oxygen bridges into a hydrocarbon backbone leads to an enhanced stability of these molecular precursors under ambient condition; however, it has also a distinct influence on their adsorption and self-Assembly on metal surfaces. Here, a low-Temperature scanning tunneling microscopy (LT-STM) study of two different epoxyacenes on the Au(111) surface at submonolayer coverage is presented. Both molecules show self-Assembly based on hydrogen bonding. While for the molecules with a single epoxy moiety nanostructures of three molecules are formed, extended molecular networks are achieved with two epoxy moieties and a slightly higher surface coverage. Upon annealing at 390 K, the molecules are reduced to the respective acene; however, both systems keep a similar assembled structure. The experimental STM images supported by theoretical calculations show that the self-Assembly of the on-surface fabricated acenes is greatly influenced by the on-surface reaction and strongly differs from the adsorption pattern of directly deposited acenes, highlighting the importance of the cleaved oxygen in the self-Assembly. © 2017 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Modeling of magnetic hystereses in soft MREs filled with NdFeB particles
    • K. A. Kalina, J. Brummund, P. Metsch, M. Kästner, D. Y. Borin, J. M. Linke, S. Odenbach
    • Smart Materials and Structures 26, 105019 (2017)
    • DOI   Abstract  

      Herein, we investigate the structure-property relationships of soft magnetorheological elastomers (MREs) filled with remanently magnetizable particles. The study is motivated from experimental results which indicate a large difference between the magnetization loops of soft MREs filled with NdFeB particles and the loops of such particles embedded in a comparatively stiff matrix, e.g. an epoxy resin. We present a microscale model for MREs based on a general continuum formulation of the magnetomechanical boundary value problem which is valid for finite strains. In particular, we develop an energetically consistent constitutive model for the hysteretic magnetization behavior of the magnetically hard particles. The microstructure is discretized and the problem is solved numerically in terms of a coupled nonlinear finite element approach. Since the local magnetic and mechanical fields are resolved explicitly inside the heterogeneous microstructure of the MRE, our model also accounts for interactions of particles close to each other. In order to connect the microscopic fields to effective macroscopic quantities of the MRE, a suitable computational homogenization scheme is used. Based on this modeling approach, it is demonstrated that the observable macroscopic behavior of the considered MREs results from the rotation of the embedded particles. Furthermore, the performed numerical simulations indicate that the reversion of the sample’s magnetization occurs due to a combination of particle rotations and internal domain conversion processes. All of our simulation results obtained for such materials are in a good qualitative agreement with the experiments. © 2017 IOP Publishing Ltd.

      @ARTICLE{Kalina2017,
      author={Kalina, K.A. and Brummund, J. and Metsch, P. and Kästner, M. and Borin, D.Y. and Linke, J.M. and Odenbach, S.},
      title={Modeling of magnetic hystereses in soft MREs filled with NdFeB particles},
      journal={Smart Materials and Structures},
      year={2017},
      volume={26},
      number={10},
      doi={10.1088/1361-665X/aa7f81},
      art_number={105019},
      note={cited By 34},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030175160&doi=10.1088%2f1361-665X%2faa7f81&partnerID=40&md5=a46b1154e70d2010739df9428bf38cf8},
      affiliation={Department of Computational and Experimental Solid Mechanics, TU Dresden, Dresden, D-01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, D-01062, Germany; Department of Magnetofluiddynamics, Measuring and Automation Technology, TU Dresden, Dresden, D-01062, Germany},
      abstract={Herein, we investigate the structure-property relationships of soft magnetorheological elastomers (MREs) filled with remanently magnetizable particles. The study is motivated from experimental results which indicate a large difference between the magnetization loops of soft MREs filled with NdFeB particles and the loops of such particles embedded in a comparatively stiff matrix, e.g. an epoxy resin. We present a microscale model for MREs based on a general continuum formulation of the magnetomechanical boundary value problem which is valid for finite strains. In particular, we develop an energetically consistent constitutive model for the hysteretic magnetization behavior of the magnetically hard particles. The microstructure is discretized and the problem is solved numerically in terms of a coupled nonlinear finite element approach. Since the local magnetic and mechanical fields are resolved explicitly inside the heterogeneous microstructure of the MRE, our model also accounts for interactions of particles close to each other. In order to connect the microscopic fields to effective macroscopic quantities of the MRE, a suitable computational homogenization scheme is used. Based on this modeling approach, it is demonstrated that the observable macroscopic behavior of the considered MREs results from the rotation of the embedded particles. Furthermore, the performed numerical simulations indicate that the reversion of the sample's magnetization occurs due to a combination of particle rotations and internal domain conversion processes. All of our simulation results obtained for such materials are in a good qualitative agreement with the experiments. © 2017 IOP Publishing Ltd.},
      author_keywords={finite element modeling; homogenization; hysteresis; magnetorheological elastomers; magnetostriction; remanent magnetization},
      document_type={Article},
      source={Scopus},
      }

  • Approaches for process and structural finite element simulations of braided ligament replacements
    • T. Gereke, O. Döbrich, D. Aibibu, J. Nowotny, C. Cherif
    • Journal of Industrial Textiles 47, 408-425 (2017)
    • DOI   Abstract  

      To prevent the renewed rupture of ligaments and tendons prior to the completed healing process, which frequently occurs in treated ruptured tendons, a temporary support structure is envisaged. The limitations of current grafts have motivated the investigation of tissue-engineered ligament replacements based on the braiding technology. This technology offers a wide range of flexibility and adjustable geometrical and structural parameters. The presented work demonstrates the possible range for tailoring the mechanical properties of polyester braids and a variation of the braiding process parameters. A finite element simulation model of the braiding process was developed, which allows the optimization of production parameters without the performance of further experimental trials. In a second modelling and simulation step, mechanical properties of the braided structures were virtually determined and compared with actual tests. The digital element approach was used for the yarns in the numerical model. The results show very good agreement for the process model in terms of braiding angles and good agreement for the structural model in terms of force-strain behaviour. With a few adaptions, the models can, thus, be applied to actual ligament replacements made of resorbable polymers. © 2016, © The Author(s) 2016.

      @ARTICLE{Gereke2017408,
      author={Gereke, T. and Döbrich, O. and Aibibu, D. and Nowotny, J. and Cherif, C.},
      title={Approaches for process and structural finite element simulations of braided ligament replacements},
      journal={Journal of Industrial Textiles},
      year={2017},
      volume={47},
      number={3},
      pages={408-425},
      doi={10.1177/1528083716648765},
      note={cited By 2},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027509592&doi=10.1177%2f1528083716648765&partnerID=40&md5=b9ee84d281b59e0bfbc63cb6e1003eb5},
      affiliation={Technische Universität Dresden, Institute of Textile Machinery and High Performance Material Technology, Germany; Technische Universität Dresden, Dresden Center for Computational Materials Science (DCMS), Germany; Technische Universität Dresden, Centre for Translational Bone, Joint and Soft Tissue Research, Germany},
      abstract={To prevent the renewed rupture of ligaments and tendons prior to the completed healing process, which frequently occurs in treated ruptured tendons, a temporary support structure is envisaged. The limitations of current grafts have motivated the investigation of tissue-engineered ligament replacements based on the braiding technology. This technology offers a wide range of flexibility and adjustable geometrical and structural parameters. The presented work demonstrates the possible range for tailoring the mechanical properties of polyester braids and a variation of the braiding process parameters. A finite element simulation model of the braiding process was developed, which allows the optimization of production parameters without the performance of further experimental trials. In a second modelling and simulation step, mechanical properties of the braided structures were virtually determined and compared with actual tests. The digital element approach was used for the yarns in the numerical model. The results show very good agreement for the process model in terms of braiding angles and good agreement for the structural model in terms of force-strain behaviour. With a few adaptions, the models can, thus, be applied to actual ligament replacements made of resorbable polymers. © 2016, © The Author(s) 2016.},
      author_keywords={Braiding; finite element model; ligament augmentation; mechanical properties; medical textiles; process simulation},
      document_type={Article},
      source={Scopus},
      }

  • In situ electron driven carbon nanopillar-fullerene transformation through Cr atom mediation
    • L. Zhao, H. Q. Ta, A. Dianat, A. Soni, A. Fediai, W. Yin, T. Gemming, B. Trzebicka, G. Cuniberti, Z. Liu, A. Bachmatiuk, M. H. Rummeli
    • Nano Letters 17, 4725-4732 (2017)
    • DOI   Abstract  

      The promise of sp2 nanomaterials remains immense, and ways to strategically combine and manipulate these nanostructures will further enhance their potential as well as advance nanotechnology as a whole. The scale of these structures requires precision at the atomic scale. In this sense electron microscopes are attractive as they offer both atomic imaging and a means to structurally modify structures. Here we show how Cr atoms can be used as physical linkers to connect carbon nanotubes and fullerenes to graphene. Crucially, while under electron irradiation, the Cr atoms can drive transformations such as catalytic healing of a hole in graphene with simultaneous transformation of a single wall carbon nanotube into a fullerene. The atomic resolution of the electron microscopy along with density functional theory based total energy calculations provide insight into the dynamic transformations of Cr atom linkers. The work augments the potential of transmission electron microscopes as nanolaboratories. © 2017 American Chemical Society.

      @ARTICLE{Zhao20174725,
      author={Zhao, L. and Ta, H.Q. and Dianat, A. and Soni, A. and Fediai, A. and Yin, W. and Gemming, T. and Trzebicka, B. and Cuniberti, G. and Liu, Z. and Bachmatiuk, A. and Rummeli, M.H.},
      title={In situ electron driven carbon nanopillar-fullerene transformation through Cr atom mediation},
      journal={Nano Letters},
      year={2017},
      volume={17},
      number={8},
      pages={4725-4732},
      doi={10.1021/acs.nanolett.7b01406},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027223954&doi=10.1021%2facs.nanolett.7b01406&partnerID=40&md5=11f6fd23733090c0193b02563f5413f0},
      affiliation={Soochow Institute for Energy and Materials Innovations, College of Physics, Optoelectronics and Energy, Collaborative Innovation Center of Suzhou Nano Science and Technology, Key Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu Province, Soochow University, Suzhou, 215006, China; Centre of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie-Sklodowskiej 34, Zabrze, 41-819, Poland; Institute for Materials Science and Max Bergman Center of Biomaterials, Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Institute of Nanotechnology, KIT, Karlsruhe, Hermann von Helmholtz-Platz 1, Eggenstein-Leopoldshafen, 76344, Germany; IFW Dresden, P.O. Box D, Dresden, 01171, Germany; Center for Nanochemistry, Beijing Science and Engineering Centre for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China},
      abstract={The promise of sp2 nanomaterials remains immense, and ways to strategically combine and manipulate these nanostructures will further enhance their potential as well as advance nanotechnology as a whole. The scale of these structures requires precision at the atomic scale. In this sense electron microscopes are attractive as they offer both atomic imaging and a means to structurally modify structures. Here we show how Cr atoms can be used as physical linkers to connect carbon nanotubes and fullerenes to graphene. Crucially, while under electron irradiation, the Cr atoms can drive transformations such as catalytic healing of a hole in graphene with simultaneous transformation of a single wall carbon nanotube into a fullerene. The atomic resolution of the electron microscopy along with density functional theory based total energy calculations provide insight into the dynamic transformations of Cr atom linkers. The work augments the potential of transmission electron microscopes as nanolaboratories. © 2017 American Chemical Society.},
      author_keywords={carbon nanotube; Cr atoms; dynamic transformations; In situ TEM; pillared graphene},
      document_type={Article},
      source={Scopus},
      }

  • Controlling the energy of defects and interfaces in the amplitude expansion of the phase-field crystal model
    • M. Salvalaglio, R. Backofen, A. Voigt, K. R. Elder
    • Physical Review E 96, 023301 (2017)
    • DOI   Abstract  

      One of the major difficulties in employing phase-field crystal (PFC) modeling and the associated amplitude (APFC) formulation is the ability to tune model parameters to match experimental quantities. In this work, we address the problem of tuning the defect core and interface energies in the APFC formulation. We show that the addition of a single term to the free-energy functional can be used to increase the solid-liquid interface and defect energies in a well-controlled fashion, without any major change to other features. The influence of the newly added term is explored in two-dimensional triangular and honeycomb structures as well as bcc and fcc lattices in three dimensions. In addition, a finite-element method (FEM) is developed for the model that incorporates a mesh refinement scheme. The combination of the FEM and mesh refinement to simulate amplitude expansion with a new energy term provides a method of controlling microscopic features such as defect and interface energies while simultaneously delivering a coarse-grained examination of the system. © 2017 American Physical Society.

      @ARTICLE{Salvalaglio2017,
      author={Salvalaglio, M. and Backofen, R. and Voigt, A. and Elder, K.R.},
      title={Controlling the energy of defects and interfaces in the amplitude expansion of the phase-field crystal model},
      journal={Physical Review E},
      year={2017},
      volume={96},
      number={2},
      doi={10.1103/PhysRevE.96.023301},
      art_number={023301},
      note={cited By 11},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028753373&doi=10.1103%2fPhysRevE.96.023301&partnerID=40&md5=8ce6f4f9640ee5781797854010a294d8},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Department of Physics, Oakland University, Rochester, MI 48309, United States},
      abstract={One of the major difficulties in employing phase-field crystal (PFC) modeling and the associated amplitude (APFC) formulation is the ability to tune model parameters to match experimental quantities. In this work, we address the problem of tuning the defect core and interface energies in the APFC formulation. We show that the addition of a single term to the free-energy functional can be used to increase the solid-liquid interface and defect energies in a well-controlled fashion, without any major change to other features. The influence of the newly added term is explored in two-dimensional triangular and honeycomb structures as well as bcc and fcc lattices in three dimensions. In addition, a finite-element method (FEM) is developed for the model that incorporates a mesh refinement scheme. The combination of the FEM and mesh refinement to simulate amplitude expansion with a new energy term provides a method of controlling microscopic features such as defect and interface energies while simultaneously delivering a coarse-grained examination of the system. © 2017 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Active forming manipulation of composite reinforcements for the suppression of forming defects
    • F. Nosrat Nezami, T. Gereke, C. Cherif
    • Composites Part A: Applied Science and Manufacturing 99, 94-101 (2017)
    • DOI   Abstract  

      For composite applications in automotive serial production, reinforcement textiles are brought into the desired shape by forming processes. The preform quality depends on the interacting factors of tool geometry, textile material, and forming process. The primary cause of defects in multilayer draping is relative movements of the plies, and the occurrence of wrinkles. Thus, the reduction of the interactions between plies is crucial to enhance preform quality. This was achieved with active metal sheets between the fabric layers. Those intermediate layers are additionally stimulated with piezo actors to reduce friction. Additional local and ply-specific clamping of layers was achieved with tension rods and segmented actuators. Defects and wrinkles in the preform could be eliminated or reduced significantly and fiber orientation could be controlled. Thus, a forming process providing high-quality preforms from multiple fabric layers was developed. Furthermore, automation complexity could be reduced significantly by utilizing rigid interlayers. © 2017 Elsevier Ltd

      @ARTICLE{NosratNezami201794,
      author={Nosrat Nezami, F. and Gereke, T. and Cherif, C.},
      title={Active forming manipulation of composite reinforcements for the suppression of forming defects},
      journal={Composites Part A: Applied Science and Manufacturing},
      year={2017},
      volume={99},
      pages={94-101},
      doi={10.1016/j.compositesa.2017.04.011},
      note={cited By 21},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018521987&doi=10.1016%2fj.compositesa.2017.04.011&partnerID=40&md5=957dcd4496848acc51e46b941cdc4a4f},
      affiliation={CIKONI Composites Innovation, Stuttgart, 70569, Germany; Technische Universität Dresden, Institute of Textile Machinery and High Performance Material Technology (ITM), Dresden, 01062, Germany; Technische Universität Dresden, Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany},
      abstract={For composite applications in automotive serial production, reinforcement textiles are brought into the desired shape by forming processes. The preform quality depends on the interacting factors of tool geometry, textile material, and forming process. The primary cause of defects in multilayer draping is relative movements of the plies, and the occurrence of wrinkles. Thus, the reduction of the interactions between plies is crucial to enhance preform quality. This was achieved with active metal sheets between the fabric layers. Those intermediate layers are additionally stimulated with piezo actors to reduce friction. Additional local and ply-specific clamping of layers was achieved with tension rods and segmented actuators. Defects and wrinkles in the preform could be eliminated or reduced significantly and fiber orientation could be controlled. Thus, a forming process providing high-quality preforms from multiple fabric layers was developed. Furthermore, automation complexity could be reduced significantly by utilizing rigid interlayers. © 2017 Elsevier Ltd},
      author_keywords={A. Carbon fibers; A. Fabrics/textiles; C. Process modelling; E. Forming},
      document_type={Article},
      source={Scopus},
      }

  • The relaxed-polar mechanism of locally optimal Cosserat rotations for an idealized nanoindentation and comparison with 3D-EBSD experiments
    • A. Fischle, P. Neff, D. Raabe
    • Zeitschrift fur Angewandte Mathematik und Physik 68, 90 (2017)
    • DOI   Abstract  

      The rotation polar (F) ∈ SO (3) arises as the unique orthogonal factor of the right polar decomposition F=polar(F)U of a given invertible matrix F∈ GL +(3). In the context of nonlinear elasticity Grioli (Boll Un Math Ital 2:252–255, 1940) discovered a geometric variational characterization of polar (F) as a unique energy-minimizing rotation. In preceding works, we have analyzed a generalization of Grioli’s variational approach with weights (material parameters) μ> 0 and μc≥ 0 (Grioli: μ= μc). The energy subject to minimization coincides with the Cosserat shear–stretch contribution arising in any geometrically nonlinear, isotropic and quadratic Cosserat continuum model formulated in the deformation gradient field F: = ∇ φ: Ω → GL +(3) and the microrotation field R: Ω → SO (3). The corresponding set of non-classical energy-minimizing rotations rpolarμ,μc±(F):=arg minR∈SO(3){Wμ,μc(R;F):=μ||sym(RTF-1)||2+μc||skew(RTF-1)||2}represents a new relaxed-polar mechanism. Our goal is to motivate this mechanism by presenting it in a relevant setting. To this end, we explicitly construct a deformation mapping φnano which models an idealized nanoindentation and compare the corresponding optimal rotation patterns rpolar1,0±(Fnano) with experimentally obtained 3D-EBSD measurements of the disorientation angle of lattice rotations due to a nanoindentation in solid copper. We observe that the non-classical relaxed-polar mechanism can produce interesting counter-rotations. A possible link between Cosserat theory and finite multiplicative plasticity theory on small scales is also explored. © 2017, Springer International Publishing AG.

      @ARTICLE{Fischle2017,
      author={Fischle, A. and Neff, P. and Raabe, D.},
      title={The relaxed-polar mechanism of locally optimal Cosserat rotations for an idealized nanoindentation and comparison with 3D-EBSD experiments},
      journal={Zeitschrift fur Angewandte Mathematik und Physik},
      year={2017},
      volume={68},
      number={4},
      doi={10.1007/s00033-017-0834-4},
      art_number={90},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026744572&doi=10.1007%2fs00033-017-0834-4&partnerID=40&md5=3d092e7ab6b79c426b68211fdcbe389e},
      affiliation={Institut für Numerische Mathematik, TU Dresden, Zellescher Weg 12-14, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, Germany; Head of Lehrstuhl für Nichtlineare Analysis und Modellierung Fakultät für Mathematik, Universität Duisburg-Essen, Thea-Leymann Str. 9, Essen, 45127, Germany; Max-Planck-Institut für Eisenforschung, Max-Planck-Str. 1, Düsseldorf, 40237, Germany},
      abstract={The rotation polar (F) ∈ SO (3) arises as the unique orthogonal factor of the right polar decomposition F=polar(F)U of a given invertible matrix F∈ GL +(3). In the context of nonlinear elasticity Grioli (Boll Un Math Ital 2:252–255, 1940) discovered a geometric variational characterization of polar (F) as a unique energy-minimizing rotation. In preceding works, we have analyzed a generalization of Grioli’s variational approach with weights (material parameters) μ> 0 and μc≥ 0 (Grioli: μ= μc). The energy subject to minimization coincides with the Cosserat shear–stretch contribution arising in any geometrically nonlinear, isotropic and quadratic Cosserat continuum model formulated in the deformation gradient field F: = ∇ φ: Ω → GL +(3) and the microrotation field R: Ω → SO (3). The corresponding set of non-classical energy-minimizing rotations rpolarμ,μc±(F):=arg minR∈SO(3){Wμ,μc(R;F):=μ||sym(RTF-1)||2+μc||skew(RTF-1)||2}represents a new relaxed-polar mechanism. Our goal is to motivate this mechanism by presenting it in a relevant setting. To this end, we explicitly construct a deformation mapping φnano which models an idealized nanoindentation and compare the corresponding optimal rotation patterns rpolar1,0±(Fnano) with experimentally obtained 3D-EBSD measurements of the disorientation angle of lattice rotations due to a nanoindentation in solid copper. We observe that the non-classical relaxed-polar mechanism can produce interesting counter-rotations. A possible link between Cosserat theory and finite multiplicative plasticity theory on small scales is also explored. © 2017, Springer International Publishing AG.},
      author_keywords={3D-EBSD; Cosserat; Cosserat couple modulus; Counter-rotations; Grioli’s theorem; Micropolar; Nanoindentation; Non-symmetric stretch; Relaxed-polar mechanism; Rotations},
      document_type={Article},
      source={Scopus},
      }

  • Photocatalytic degradation of recalcitrant micropollutants by reusable Fe3O4/SiO2/TiO2 particles
    • S. Teixeira, H. Mora, L. -M. Blasse, P. M. Martins, S. A. C. Carabineiro, S. Lanceros-Méndez, K. Kühn, G. Cuniberti
    • Journal of Photochemistry and Photobiology A: Chemistry 345, 27-35 (2017)
    • DOI   Abstract  

      Photocatalysis promotes the degradation of contaminants in water, transforming them into by-products with lower or no toxicity. The photocatalysts can be applied in suspension or immobilized onto a support. The aim of using the immobilized form against the suspension form is that the costly extra final filtration process can be avoided, which is particularly important in water decontamination. This work reports on reusable Fe3O4/SiO2/TiO2 particles and the assessment of their photocatalytic activity on the degradation of methylene blue (MB), ciprofloxacin (CIP), norfloxacin (NOR) and ibuprofen (IBP). To achieve the most efficient photocatalyst it is necessary to determine the optimal thermal treatment parameters therefore, the Fe3O4/SiO2/TiO2 particles were calcined at different temperatures (500 °C and 600 °C) and times (30 min and 60 min). Higher degradation rates were achieved with calcination at 600 °C, reaching a total degradation of CIP, NOR, and MB, and half of IBP. The reuse of the magnetic particles is an economic and eco-friendly way to treat polluted water. The produced Fe3O4/SiO2/TiO2 particles showed a remarkable photocatalytic degradation of recalcitrant micropollutants, without significant efficiency loss after five uses. In addition, no other works reporting on the degradation of recalcitrant micropollutants using similar magnetic particles were found in the literature. © 2017 Elsevier B.V.

      @ARTICLE{Teixeira201727,
      author={Teixeira, S. and Mora, H. and Blasse, L.-M. and Martins, P.M. and Carabineiro, S.A.C. and Lanceros-Méndez, S. and Kühn, K. and Cuniberti, G.},
      title={Photocatalytic degradation of recalcitrant micropollutants by reusable Fe3O4/SiO2/TiO2 particles},
      journal={Journal of Photochemistry and Photobiology A: Chemistry},
      year={2017},
      volume={345},
      pages={27-35},
      doi={10.1016/j.jphotochem.2017.05.024},
      note={cited By 27},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019702555&doi=10.1016%2fj.jphotochem.2017.05.024&partnerID=40&md5=97d4582e239cefde5777ebb453b15ba6},
      affiliation={Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Centro/Departamento de Física da University of Minho, Campus de Gualtar, Braga, 4710-057, Portugal; Centro de Engenharia Biológica, University of Minho, Braga, 4710-057, Portugal; IB-S – Institute for Research and Innovation on Bio-Sustainability, University of Minho Campus de Gualtar, Braga, 4710-057, Portugal; Laboratório de Catálise e Materiais (LCM), Laboratório Associado LSRE-LCM, Faculdade de Engenharia, Universidade do Porto, Porto, 4200-465, Portugal; Basque Center for Materials, Applications and Nanostructures (BCMaterials), Parque Tecnológico de Bizkaia, Ed. 500, Derio, 48160, Spain; IKERBASQUE, Basque Foundation for Science, Bilbao, 48013, Spain; Dresden Center for Computational Materials Science (DCCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden (CFAED), TU Dresden, Dresden, 01062, Germany},
      abstract={Photocatalysis promotes the degradation of contaminants in water, transforming them into by-products with lower or no toxicity. The photocatalysts can be applied in suspension or immobilized onto a support. The aim of using the immobilized form against the suspension form is that the costly extra final filtration process can be avoided, which is particularly important in water decontamination. This work reports on reusable Fe3O4/SiO2/TiO2 particles and the assessment of their photocatalytic activity on the degradation of methylene blue (MB), ciprofloxacin (CIP), norfloxacin (NOR) and ibuprofen (IBP). To achieve the most efficient photocatalyst it is necessary to determine the optimal thermal treatment parameters therefore, the Fe3O4/SiO2/TiO2 particles were calcined at different temperatures (500 °C and 600 °C) and times (30 min and 60 min). Higher degradation rates were achieved with calcination at 600 °C, reaching a total degradation of CIP, NOR, and MB, and half of IBP. The reuse of the magnetic particles is an economic and eco-friendly way to treat polluted water. The produced Fe3O4/SiO2/TiO2 particles showed a remarkable photocatalytic degradation of recalcitrant micropollutants, without significant efficiency loss after five uses. In addition, no other works reporting on the degradation of recalcitrant micropollutants using similar magnetic particles were found in the literature. © 2017 Elsevier B.V.},
      author_keywords={Dyes; Immobilization; Magnetic; Pharmaceuticals; Remediation},
      document_type={Article},
      source={Scopus},
      }

  • Ab initio study of electron-phonon coupling in rubrene
    • P. Ordejón, D. Boskovic, M. Panhans, F. Ortmann
    • Physical Review B 96, 035202 (2017)
    • DOI   Abstract  

      The use of ab initio methods for accurate simulations of electronic, phononic, and electron-phonon properties of molecular materials such as organic crystals is a challenge that is often tackled stepwise based on molecular properties calculated in gas phase and perturbatively treated parameters relevant for solid phases. In contrast, in this work we report a full first-principles description of such properties for the prototypical rubrene crystals. More specifically, we determine a Holstein-Peierls-type Hamiltonian for rubrene, including local and nonlocal electron-phonon couplings. Thereby, a recipe for circumventing the issue of numerical inaccuracies with low-frequency phonons is presented. In addition, we study the phenyl group motion with a molecular dynamics approach. © 2017 American Physical Society.

      @ARTICLE{Ordejón2017,
      author={Ordejón, P. and Boskovic, D. and Panhans, M. and Ortmann, F.},
      title={Ab initio study of electron-phonon coupling in rubrene},
      journal={Physical Review B},
      year={2017},
      volume={96},
      number={3},
      doi={10.1103/PhysRevB.96.035202},
      art_number={035202},
      note={cited By 18},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026448874&doi=10.1103%2fPhysRevB.96.035202&partnerID=40&md5=9af0420d285b858dd84c45984dd9baa9},
      affiliation={Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, BIST, Campus UAB, Bellaterra, Barcelona, E-08193, Spain; Center for Advancing Electronics Dresden, Institute for Materials Science, Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={The use of ab initio methods for accurate simulations of electronic, phononic, and electron-phonon properties of molecular materials such as organic crystals is a challenge that is often tackled stepwise based on molecular properties calculated in gas phase and perturbatively treated parameters relevant for solid phases. In contrast, in this work we report a full first-principles description of such properties for the prototypical rubrene crystals. More specifically, we determine a Holstein-Peierls-type Hamiltonian for rubrene, including local and nonlocal electron-phonon couplings. Thereby, a recipe for circumventing the issue of numerical inaccuracies with low-frequency phonons is presented. In addition, we study the phenyl group motion with a molecular dynamics approach. © 2017 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Tuning Near-Infrared Absorbing Donor Materials: A Study of Electronic, Optical, and Charge-Transport Properties of aza-BODIPYs
    • K. S. Schellhammer, T. -Y. Li, O. Zeika, C. Körner, K. Leo, F. Ortmann, G. Cuniberti
    • Chemistry of Materials 29, 5525-5536 (2017)
    • DOI   Abstract  

      The class of 4,4′-difluoro-4-bora-3a,4a,8-triaza-s-indacenes (aza-BODIPYs) are promising near-infrared absorber materials which are successfully used in organic solar cells to extend their absorption to the near-infrared regime. We computationally studied electronic properties, internal reorganization energies, and the optical properties of more than 100 promising candidates and derived design principles, including novel functionalization routes, to improve their performance as donor materials. We synthesized and characterized several of the promising molecules, confirming the predicted trends. The best charge transport properties and absorption characteristics are obtained for naphthalene-annulated molecular cores due to optimally delocalized frontier molecular orbitals. Further optimization can be achieved by α-functionalization with fluorinated groups, β-functionalization with accepting substituents, and modification of the borondifluoride group. For such molecules, we predict a bathochromic shift in the absorption, which should not significantly reduce the open-circuit voltage. Torsional restriction of α-substituents by carbon bridges can further improve both charge transport and absorption. The theoretically and experimentally observed independence of most of the functionalization strategies makes BODIPYs an ideal material class for tailor-made absorber materials that can cover a broad range of absorption, charge transport, and energetic regimes, calling for further exploration in organic solar cell applications, fluorescence microscopy, and photodynamic therapy. © 2017 American Chemical Society.

      @ARTICLE{Schellhammer20175525,
      author={Schellhammer, K.S. and Li, T.-Y. and Zeika, O. and Körner, C. and Leo, K. and Ortmann, F. and Cuniberti, G.},
      title={Tuning Near-Infrared Absorbing Donor Materials: A Study of Electronic, Optical, and Charge-Transport Properties of aza-BODIPYs},
      journal={Chemistry of Materials},
      year={2017},
      volume={29},
      number={13},
      pages={5525-5536},
      doi={10.1021/acs.chemmater.7b00653},
      note={cited By 18},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85022344367&doi=10.1021%2facs.chemmater.7b00653&partnerID=40&md5=cd7966a9f9797a79cba5d84c12d3b019},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, 01062, Germany; Institut für Angewandte Photophysik, Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={The class of 4,4′-difluoro-4-bora-3a,4a,8-triaza-s-indacenes (aza-BODIPYs) are promising near-infrared absorber materials which are successfully used in organic solar cells to extend their absorption to the near-infrared regime. We computationally studied electronic properties, internal reorganization energies, and the optical properties of more than 100 promising candidates and derived design principles, including novel functionalization routes, to improve their performance as donor materials. We synthesized and characterized several of the promising molecules, confirming the predicted trends. The best charge transport properties and absorption characteristics are obtained for naphthalene-annulated molecular cores due to optimally delocalized frontier molecular orbitals. Further optimization can be achieved by α-functionalization with fluorinated groups, β-functionalization with accepting substituents, and modification of the borondifluoride group. For such molecules, we predict a bathochromic shift in the absorption, which should not significantly reduce the open-circuit voltage. Torsional restriction of α-substituents by carbon bridges can further improve both charge transport and absorption. The theoretically and experimentally observed independence of most of the functionalization strategies makes BODIPYs an ideal material class for tailor-made absorber materials that can cover a broad range of absorption, charge transport, and energetic regimes, calling for further exploration in organic solar cell applications, fluorescence microscopy, and photodynamic therapy. © 2017 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Modeling the effects of lanthanum, nitrogen, and fluorine treatments of Si-SiON-HfO2-TiN gate stacks in 28 nm high-k-metal gate technology
    • R. Leitsmann, F. Lazarevic, M. Drescher, E. Erben
    • Journal of Applied Physics 121, 234501 (2017)
    • DOI   Abstract  

      We have carried out a combined experimental and theoretical study on the influence of lanthanum, nitrogen, and fluorine treatments on the electric properties of high-k metal gate (HKMG) devices. In particular, we have developed a theoretical gate stack model which is able to predict qualitatively and quantitatively the influence of nitrogen, fluorine, and lanthanum treatments on the characteristic electric properties of Si-SiON-HfO2 gate stacks. The combination of this theoretical model with experimental investigations of several differently treated HKMG devices allows the estimation of the amount of incorporated impurity atoms in different material layers. Furthermore, we propose an atomistic mechanism for the incorporation of lanthanum and fluorine impurity atoms and we can explain the results of recent leakage current measurements by a passivation of oxygen vacancies within the HfO2 layer. © 2017 Author(s).

      @ARTICLE{Leitsmann2017,
      author={Leitsmann, R. and Lazarevic, F. and Drescher, M. and Erben, E.},
      title={Modeling the effects of lanthanum, nitrogen, and fluorine treatments of Si-SiON-HfO2-TiN gate stacks in 28 nm high-k-metal gate technology},
      journal={Journal of Applied Physics},
      year={2017},
      volume={121},
      number={23},
      doi={10.1063/1.4986494},
      art_number={234501},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021171535&doi=10.1063%2f1.4986494&partnerID=40&md5=c1ac1b40d491321b0f43bb51452d5a75},
      affiliation={AQcomputare Gesellschaft für Materialberechnung MbH, Annaberger Str. 240, Chemnitz, 09125, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01069, Germany; Fraunhofer IPMS-CNT, Königsbrückerstr. 178, Dresden, 01099, Germany; Globalfoundries, Wilschdorfer Landstr. 101, Dresden, 01109, Germany},
      abstract={We have carried out a combined experimental and theoretical study on the influence of lanthanum, nitrogen, and fluorine treatments on the electric properties of high-k metal gate (HKMG) devices. In particular, we have developed a theoretical gate stack model which is able to predict qualitatively and quantitatively the influence of nitrogen, fluorine, and lanthanum treatments on the characteristic electric properties of Si-SiON-HfO2 gate stacks. The combination of this theoretical model with experimental investigations of several differently treated HKMG devices allows the estimation of the amount of incorporated impurity atoms in different material layers. Furthermore, we propose an atomistic mechanism for the incorporation of lanthanum and fluorine impurity atoms and we can explain the results of recent leakage current measurements by a passivation of oxygen vacancies within the HfO2 layer. © 2017 Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Microscale simulation of adhesive and cohesive failure in rough interfaces
    • F. Hirsch, M. Kästner
    • Engineering Fracture Mechanics 178, 416-432 (2017)
    • DOI   Abstract  

      Multi-material lightweight designs, e.g. the combination of aluminum with fiber-reinforced composites, are a key feature for the development of innovative and resource-efficient products. The connection properties of such bi-material interfaces are influenced by the geometric structure on different length scales. In this article a modeling strategy is presented to study the failure behavior of rough interfaces within a computational homogenization scheme. We study different local phenomena and their effects on the overall interface characteristics, e.g. the surface roughness and different local failure types as cohesive failure of the bulk material and adhesive failure of the local interface. Since there is a large separation in the length scales of the surface roughness, which is in the micrometer range, and conventional structural components, we employ a numerical homogenization approach to extract effective traction-separation laws to derive effective interface parameters. Adhesive interface failure is modeled by cohesive elements based on a traction-separation law and cohesive failure of the bulk material is described by an elastic-plastic model with progressive damage evolution. © 2017 Elsevier Ltd

      @ARTICLE{Hirsch2017416,
      author={Hirsch, F. and Kästner, M.},
      title={Microscale simulation of adhesive and cohesive failure in rough interfaces},
      journal={Engineering Fracture Mechanics},
      year={2017},
      volume={178},
      pages={416-432},
      doi={10.1016/j.engfracmech.2017.02.026},
      note={cited By 12},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017120386&doi=10.1016%2fj.engfracmech.2017.02.026&partnerID=40&md5=e7d46e90ef06f2bd7864c847722f6cf5},
      affiliation={Institute of Solid Mechanics, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={Multi-material lightweight designs, e.g. the combination of aluminum with fiber-reinforced composites, are a key feature for the development of innovative and resource-efficient products. The connection properties of such bi-material interfaces are influenced by the geometric structure on different length scales. In this article a modeling strategy is presented to study the failure behavior of rough interfaces within a computational homogenization scheme. We study different local phenomena and their effects on the overall interface characteristics, e.g. the surface roughness and different local failure types as cohesive failure of the bulk material and adhesive failure of the local interface. Since there is a large separation in the length scales of the surface roughness, which is in the micrometer range, and conventional structural components, we employ a numerical homogenization approach to extract effective traction-separation laws to derive effective interface parameters. Adhesive interface failure is modeled by cohesive elements based on a traction-separation law and cohesive failure of the bulk material is described by an elastic-plastic model with progressive damage evolution. © 2017 Elsevier Ltd},
      author_keywords={Cohesive zone modeling; Homogenization; Hybrid materials; Interface fracture},
      document_type={Article},
      source={Scopus},
      }

  • Doping of graphene induced by boron/silicon substrate
    • A. Dianat, Z. Liao, M. Gall, T. Zhang, R. Gutierrez, E. Zschech, G. Cuniberti
    • Nanotechnology 28, 215701 (2017)
    • DOI   Abstract  

      In this work, we show the doping of graphene most likely from heteroatoms induced by the substrate using Raman spectra, x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy and ab initio molecular dynamics (MD) simulations. The doping of graphene on a highly boron-doped silicon substrate was achieved by an annealing at 400 K for about 3 h in an oven with air flow. With the same annealing, only the Raman features similar to that from the pristine graphene were observed in the freestanding graphene and the graphene on a typical Si/SiO2 wafer. Ab initio MD simulations were performed for defected graphene on boron-doped silicon substrate at several temperatures. All vacancy sites in the graphene are occupied either with B atoms or Si atoms resulting in the mixed boron-silicon doping of the graphene. The MD simulations validated the experimetal finding of graphene doped behavior observed by Raman spectrum. The electronic structure analysis indicated the p-type nature of doped graphene. The observed doping by the possible incorporation of heteroatoms into the graphene, simply only using 400 K annealing the boron-doped Si substrate, could provide a new approach to synthesize doped graphene in a more economic way. © 2017 IOP Publishing Ltd.

      @ARTICLE{Dianat2017,
      author={Dianat, A. and Liao, Z. and Gall, M. and Zhang, T. and Gutierrez, R. and Zschech, E. and Cuniberti, G.},
      title={Doping of graphene induced by boron/silicon substrate},
      journal={Nanotechnology},
      year={2017},
      volume={28},
      number={21},
      doi={10.1088/1361-6528/aa6ce9},
      art_number={215701},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019114731&doi=10.1088%2f1361-6528%2faa6ce9&partnerID=40&md5=63e6272a67297ba78f2c30cdb865c88e},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, D-01062, Germany; Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), Dresden, D-01109, Germany; Department for Molecular Functional Materials, TU Dresden, Dresden, D-01069, Germany; Dresden Center for Nanoanalysis (DCN), TU Dresden, Dresden, D-01187, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, D-01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, D-01062, Germany},
      abstract={In this work, we show the doping of graphene most likely from heteroatoms induced by the substrate using Raman spectra, x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy and ab initio molecular dynamics (MD) simulations. The doping of graphene on a highly boron-doped silicon substrate was achieved by an annealing at 400 K for about 3 h in an oven with air flow. With the same annealing, only the Raman features similar to that from the pristine graphene were observed in the freestanding graphene and the graphene on a typical Si/SiO2 wafer. Ab initio MD simulations were performed for defected graphene on boron-doped silicon substrate at several temperatures. All vacancy sites in the graphene are occupied either with B atoms or Si atoms resulting in the mixed boron-silicon doping of the graphene. The MD simulations validated the experimetal finding of graphene doped behavior observed by Raman spectrum. The electronic structure analysis indicated the p-type nature of doped graphene. The observed doping by the possible incorporation of heteroatoms into the graphene, simply only using 400 K annealing the boron-doped Si substrate, could provide a new approach to synthesize doped graphene in a more economic way. © 2017 IOP Publishing Ltd.},
      author_keywords={annealing; doping; graphene; heteroatoms},
      document_type={Article},
      source={Scopus},
      }

  • Polycyclic heteroaromatic hydrocarbons containing a benzoisoindole core
    • M. Richter, K. S. Schellhammer, P. MacHata, G. Cuniberti, A. Popov, F. Ortmann, R. Berger, K. Müllen, X. Feng
    • Organic Chemistry Frontiers 4, 847-852 (2017)
    • DOI   Abstract  

      By the combination of 9a-azaphenalene and a perpendicularly oriented acene, we have synthesized three derivatives of a series of novel, fully-conjugated nitrogen-containing polycyclic aromatic hydrocarbons (PAHs), namely [7,8]naphtho[2′,3′:1,2]indolizino[6,5,4,3-def]phenanthridine, with an acetylene triisopropylsilyl (TIPS), phenyl or benzothiophenyl substituent. Their optoelectronic properties were studied via UV-Vis-NIR absorption, fluorescence spectroscopy and cyclic voltammetry. In addition, in situ spectroelectrochemistry was performed to investigate the optical and magnetic properties of the mono-radical cation and anion by quasi-reversible oxidation and reduction of 11-(tert-butyl)-5,17-bis((triisopropylsilyl)ethynyl)[7,8]naphtho[2′,3′:1,2]indolizino[6,5,4,3-def]phenanthridine (1a). Theoretical modelling confirmed the predominately closed-shell electronic ground state with a weak diradical character depending on the geometry. © 2017 the Partner Organisations.

      @ARTICLE{Richter2017847,
      author={Richter, M. and Schellhammer, K.S. and MacHata, P. and Cuniberti, G. and Popov, A. and Ortmann, F. and Berger, R. and Müllen, K. and Feng, X.},
      title={Polycyclic heteroaromatic hydrocarbons containing a benzoisoindole core},
      journal={Organic Chemistry Frontiers},
      year={2017},
      volume={4},
      number={5},
      pages={847-852},
      doi={10.1039/c7qo00180k},
      note={cited By 17},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021845756&doi=10.1039%2fc7qo00180k&partnerID=40&md5=cd476305ba36c1c3cdd7f1ec02284cdc},
      affiliation={Institute for Molecular Functional Materials, Center for Advancing Electronics Dresden (Cfaed), Dresden University of Technology, Dresden, 01062, Germany; Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden Center for Computational Materials Science, Dresden University of Technology, Dresden, 01062, Germany; Center of Spectroelectrochemistry, Department of Electrochemistry and Conducting Polymers, Leibniz Institute for Solid State and Materials Research, Dresden, 01069, Germany; Max Planck Institute for Polymer Research, Mainz, 55128, Germany},
      abstract={By the combination of 9a-azaphenalene and a perpendicularly oriented acene, we have synthesized three derivatives of a series of novel, fully-conjugated nitrogen-containing polycyclic aromatic hydrocarbons (PAHs), namely [7,8]naphtho[2′,3′:1,2]indolizino[6,5,4,3-def]phenanthridine, with an acetylene triisopropylsilyl (TIPS), phenyl or benzothiophenyl substituent. Their optoelectronic properties were studied via UV-Vis-NIR absorption, fluorescence spectroscopy and cyclic voltammetry. In addition, in situ spectroelectrochemistry was performed to investigate the optical and magnetic properties of the mono-radical cation and anion by quasi-reversible oxidation and reduction of 11-(tert-butyl)-5,17-bis((triisopropylsilyl)ethynyl)[7,8]naphtho[2′,3′:1,2]indolizino[6,5,4,3-def]phenanthridine (1a). Theoretical modelling confirmed the predominately closed-shell electronic ground state with a weak diradical character depending on the geometry. © 2017 the Partner Organisations.},
      document_type={Article},
      source={Scopus},
      }

  • Developing a Customized Perfusion Bioreactor Prototype with Controlled Positional Variability in Oxygen Partial Pressure for Bone and Cartilage Tissue Engineering
    • P. S. Lee, H. Eckert, R. Hess, M. Gelinsky, D. Rancourt, R. Krawetz, G. Cuniberti, D. Scharnweber
    • Tissue Engineering – Part C: Methods 23, 286-297 (2017)
    • DOI   Abstract  

      Skeletal development is a multistep process that involves the complex interplay of multiple cell types at different stages of development. Besides biochemical and physical cues, oxygen tension also plays a pivotal role in influencing cell fate during skeletal development. At physiological conditions, bone cells generally reside in a relatively oxygenated environment whereas chondrocytes reside in a hypoxic environment. However, it is technically challenging to achieve such defined, yet diverse oxygen distribution on traditional in vitro cultivation platforms. Instead, engineered osteochondral constructs are commonly cultivated in a homogeneous, stable environment. In this study, we describe a customized perfusion bioreactor having stable positional variability in oxygen tension at defined regions. Further, engineered collagen constructs were coaxed into adopting the shape and dimensions of defined cultivation platforms that were precasted in 1.5% agarose bedding. After cultivating murine embryonic stem cells that were embedded in collagen constructs for 50 days, mineralized constructs of specific dimensions and a stable structural integrity were achieved. The end-products, specifically constructs cultivated without chondroitin sulfate A (CSA), showed a significant increase in mechanical stiffness compared with their initial gel-like constructs. More importantly, the localization of osteochondral cell types was specific and corresponded to the oxygen tension gradient generated in the bioreactor. In addition, CSA in complementary with low oxygen tension was also found to be a potent inducer of chondrogenesis in this system. In summary, we have demonstrated a customized perfusion bioreactor prototype that is capable of generating a more dynamic, yet specific cultivation environment that could support propagation of multiple osteochondral lineages within a single engineered construct in vitro. Our system opens up new possibilities for in vitro research on human skeletal development. © 2017 Mary Ann Liebert, Inc.

      @ARTICLE{Lee2017286,
      author={Lee, P.S. and Eckert, H. and Hess, R. and Gelinsky, M. and Rancourt, D. and Krawetz, R. and Cuniberti, G. and Scharnweber, D.},
      title={Developing a Customized Perfusion Bioreactor Prototype with Controlled Positional Variability in Oxygen Partial Pressure for Bone and Cartilage Tissue Engineering},
      journal={Tissue Engineering - Part C: Methods},
      year={2017},
      volume={23},
      number={5},
      pages={286-297},
      doi={10.1089/ten.tec.2016.0244},
      note={cited By 9},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019498387&doi=10.1089%2ften.tec.2016.0244&partnerID=40&md5=e78e0155f84ffec9b5bfb469b144d10c},
      affiliation={Institute for Materials Science, Technische Universität Dresden, Max Bergmann Center of Biomaterials, Budapester Straße 27, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, Germany; Center for Translational Bone, Joint and Soft Tissue Research, Technische Universität Dresden, Dresden, Germany; Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, Canada; Department of Cell Biology and Anatomy, Faculty of Medicine, University of Calgary, Calgary, Canada},
      abstract={Skeletal development is a multistep process that involves the complex interplay of multiple cell types at different stages of development. Besides biochemical and physical cues, oxygen tension also plays a pivotal role in influencing cell fate during skeletal development. At physiological conditions, bone cells generally reside in a relatively oxygenated environment whereas chondrocytes reside in a hypoxic environment. However, it is technically challenging to achieve such defined, yet diverse oxygen distribution on traditional in vitro cultivation platforms. Instead, engineered osteochondral constructs are commonly cultivated in a homogeneous, stable environment. In this study, we describe a customized perfusion bioreactor having stable positional variability in oxygen tension at defined regions. Further, engineered collagen constructs were coaxed into adopting the shape and dimensions of defined cultivation platforms that were precasted in 1.5% agarose bedding. After cultivating murine embryonic stem cells that were embedded in collagen constructs for 50 days, mineralized constructs of specific dimensions and a stable structural integrity were achieved. The end-products, specifically constructs cultivated without chondroitin sulfate A (CSA), showed a significant increase in mechanical stiffness compared with their initial gel-like constructs. More importantly, the localization of osteochondral cell types was specific and corresponded to the oxygen tension gradient generated in the bioreactor. In addition, CSA in complementary with low oxygen tension was also found to be a potent inducer of chondrogenesis in this system. In summary, we have demonstrated a customized perfusion bioreactor prototype that is capable of generating a more dynamic, yet specific cultivation environment that could support propagation of multiple osteochondral lineages within a single engineered construct in vitro. Our system opens up new possibilities for in vitro research on human skeletal development. © 2017 Mary Ann Liebert, Inc.},
      author_keywords={3D cell culture; bioreactors; bone; oxygen tension; tissue engineering},
      document_type={Article},
      source={Scopus},
      }

  • Theoretical models for magneto-sensitive elastomers: A comparison between continuum and dipole approaches
    • D. Romeis, P. Metsch, M. Kästner, M. Saphiannikova
    • Physical Review E 95, 042501 (2017)
    • DOI   Abstract  

      In the literature, different theoretical models have been proposed to describe the properties of systems which consist of magnetizable particles that are embedded into an elastomer matrix. It is well known that such magneto-sensitive elastomers display a strong magneto-mechanical coupling when subjected to an external magnetic field. Nevertheless, the predictions of available models often vary significantly since they are based on different assumptions and approximations. Up to now the actual accuracy and the limits of applicability are widely unknown. In the present work, we compare the results of a microscale continuum and a dipolar mean field approach with regard to their predictions for the magnetostrictive response of magneto-sensitive elastomers and reveal some fundamental relations between the relevant quantities in both theories. It turns out that there is a very good agreement between both modeling strategies, especially for entirely random microstructures. In contrast, a comparison of the finite-element results with a modified approach, which – similar to the continuum model – is based on calculations with discrete particle distributions, reveals clear deviations. Our systematic analysis of the differences shows to what extent the dipolar mean field approach is superior to other dipole models. © 2017 American Physical Society.

      @ARTICLE{Romeis2017,
      author={Romeis, D. and Metsch, P. and Kästner, M. and Saphiannikova, M.},
      title={Theoretical models for magneto-sensitive elastomers: A comparison between continuum and dipole approaches},
      journal={Physical Review E},
      year={2017},
      volume={95},
      number={4},
      doi={10.1103/PhysRevE.95.042501},
      art_number={042501},
      note={cited By 27},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017110886&doi=10.1103%2fPhysRevE.95.042501&partnerID=40&md5=66cb7f7e0129b8fbbcff8a3f8aa7fdd3},
      affiliation={Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, Dresden, 01069, Germany; Institute of Solid Mechanics, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={In the literature, different theoretical models have been proposed to describe the properties of systems which consist of magnetizable particles that are embedded into an elastomer matrix. It is well known that such magneto-sensitive elastomers display a strong magneto-mechanical coupling when subjected to an external magnetic field. Nevertheless, the predictions of available models often vary significantly since they are based on different assumptions and approximations. Up to now the actual accuracy and the limits of applicability are widely unknown. In the present work, we compare the results of a microscale continuum and a dipolar mean field approach with regard to their predictions for the magnetostrictive response of magneto-sensitive elastomers and reveal some fundamental relations between the relevant quantities in both theories. It turns out that there is a very good agreement between both modeling strategies, especially for entirely random microstructures. In contrast, a comparison of the finite-element results with a modified approach, which - similar to the continuum model - is based on calculations with discrete particle distributions, reveals clear deviations. Our systematic analysis of the differences shows to what extent the dipolar mean field approach is superior to other dipole models. © 2017 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • In-plane edge magnetism in graphene-like nanoribbons
    • S. Krompiewski, G. Cuniberti
    • Acta Physica Polonica A 131, 828-829 (2017)
    • DOI   Abstract  

      This paper is devoted to identification of the most important factors responsible for formation of magnetic moments at edges of graphene-like nanoribbons. The main role is attributed to the Hubbard correlations (within unrestricted Hartree-Fock approximation) and intrinsic spin-orbit interactions, but additionally a perpendicular electric field is also taken into account. Of particular interest is the interplay of the in-plane edge magnetism and the energy band gap. It is shown that, with the increasing electric field, typically the following phases develop: magnetic insulator (with in-plane spins), nonmagnetic narrow-band semiconductor, and nonmagnetic band insulator.

      @ARTICLE{Krompiewski2017828,
      author={Krompiewski, S. and Cuniberti, G.},
      title={In-plane edge magnetism in graphene-like nanoribbons},
      journal={Acta Physica Polonica A},
      year={2017},
      volume={131},
      number={4},
      pages={828-829},
      doi={10.12693/APhysPolA.131.828},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019569193&doi=10.12693%2fAPhysPolA.131.828&partnerID=40&md5=fcbfd190502cca0956b891d5206cd7ec},
      affiliation={Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, Poznan, 60-179, Poland; TU Dresden, Dresden, 01062, Germany; Institute for Materials Science, Max Bergmann Center of Biomaterials, Germany; Center for Advancing Electronics Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), Germany},
      abstract={This paper is devoted to identification of the most important factors responsible for formation of magnetic moments at edges of graphene-like nanoribbons. The main role is attributed to the Hubbard correlations (within unrestricted Hartree-Fock approximation) and intrinsic spin-orbit interactions, but additionally a perpendicular electric field is also taken into account. Of particular interest is the interplay of the in-plane edge magnetism and the energy band gap. It is shown that, with the increasing electric field, typically the following phases develop: magnetic insulator (with in-plane spins), nonmagnetic narrow-band semiconductor, and nonmagnetic band insulator.},
      document_type={Conference Paper},
      source={Scopus},
      }

  • Improved recursive Green’s function formalism for quasi one-dimensional systems with realistic defects
    • F. Teichert, A. Zienert, J. Schuster, M. Schreiber
    • Journal of Computational Physics 334, 607-619 (2017)
    • DOI   Abstract  

      We derive an improved version of the recursive Green’s function formalism (RGF), which is a standard tool in the quantum transport theory. We consider the case of disordered quasi one-dimensional materials where the disorder is applied in form of randomly distributed realistic defects, leading to partly periodic Hamiltonian matrices. The algorithm accelerates the common RGF in the recursive decimation scheme, using the iteration steps of the renormalization decimation algorithm. This leads to a smaller effective system, which is treated using the common forward iteration scheme. The computational complexity scales linearly with the number of defects, instead of linearly with the total system length for the conventional approach. We show that the scaling of the calculation time of the Green’s function depends on the defect density of a random test system. Furthermore, we discuss the calculation time and the memory requirement of the whole transport formalism applied to defective carbon nanotubes. © 2017 Elsevier Inc.

      @ARTICLE{Teichert2017607,
      author={Teichert, F. and Zienert, A. and Schuster, J. and Schreiber, M.},
      title={Improved recursive Green's function formalism for quasi one-dimensional systems with realistic defects},
      journal={Journal of Computational Physics},
      year={2017},
      volume={334},
      pages={607-619},
      doi={10.1016/j.jcp.2017.01.024},
      note={cited By 6},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85009989733&doi=10.1016%2fj.jcp.2017.01.024&partnerID=40&md5=362ec035765a360e1ae7459c383b3296},
      affiliation={Institute of Physics, Faculty of Natural Sciences, Chemnitz University of Technology, Chemnitz, 09126, Germany; Center for Microtechnologies, Chemnitz University of Technology, Chemnitz, 09126, Germany; Fraunhofer Institute for Electronic Nano Systems (ENAS), Chemnitz, 09126, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={We derive an improved version of the recursive Green's function formalism (RGF), which is a standard tool in the quantum transport theory. We consider the case of disordered quasi one-dimensional materials where the disorder is applied in form of randomly distributed realistic defects, leading to partly periodic Hamiltonian matrices. The algorithm accelerates the common RGF in the recursive decimation scheme, using the iteration steps of the renormalization decimation algorithm. This leads to a smaller effective system, which is treated using the common forward iteration scheme. The computational complexity scales linearly with the number of defects, instead of linearly with the total system length for the conventional approach. We show that the scaling of the calculation time of the Green's function depends on the defect density of a random test system. Furthermore, we discuss the calculation time and the memory requirement of the whole transport formalism applied to defective carbon nanotubes. © 2017 Elsevier Inc.},
      author_keywords={Carbon nanotube (CNT); Defect; Electronic transport; Recursive Green's function formalism (RGF); Renormalization decimation algorithm (RDA)},
      document_type={Article},
      source={Scopus},
      }

  • Coordination Polymer Framework Based On-Chip Micro-Supercapacitors with AC Line-Filtering Performance
    • C. Yang, K. S. Schellhammer, F. Ortmann, S. Sun, R. Dong, M. Karakus, Z. Mics, M. Löffler, F. Zhang, X. Zhuang, E. Cánovas, G. Cuniberti, M. Bonn, X. Feng
    • Angewandte Chemie – International Edition 56, 3920-3924 (2017)
    • DOI   Abstract  

      On-chip micro-supercapacitors (MSCs) are important Si-compatible power-source backups for miniaturized electronics. Despite their tremendous advantages, current on-chip MSCs require harsh processing conditions and typically perform like resistors when filtering ripples from alternating current (AC). Herein, we demonstrated a facile layer-by-layer method towards on-chip MSCs based on an azulene-bridged coordination polymer framework (PiCBA). Owing to the good carrier mobility (5×10−3 cm2 V−1 s−1) of PiCBA, the permanent dipole moment of azulene skeleton, and ultralow band gap of PiCBA, the fabricated MSCs delivered high specific capacitances of up to 34.1 F cm−3 at 50 mV s−1 and a high volumetric power density of 1323 W cm−3. Most importantly, such MCSs exhibited AC line-filtering performance (−73° at 120 Hz) with a short resistance–capacitance constant of circa 0.83 ms. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

      @ARTICLE{Yang20173920,
      author={Yang, C. and Schellhammer, K.S. and Ortmann, F. and Sun, S. and Dong, R. and Karakus, M. and Mics, Z. and Löffler, M. and Zhang, F. and Zhuang, X. and Cánovas, E. and Cuniberti, G. and Bonn, M. and Feng, X.},
      title={Coordination Polymer Framework Based On-Chip Micro-Supercapacitors with AC Line-Filtering Performance},
      journal={Angewandte Chemie - International Edition},
      year={2017},
      volume={56},
      number={14},
      pages={3920-3924},
      doi={10.1002/anie.201700679},
      note={cited By 75},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85014708204&doi=10.1002%2fanie.201700679&partnerID=40&md5=ecd4ea2062d5fa00cd4accf54a84e2a9},
      affiliation={School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai, 200240, China; Center for Advancing Electronics Dresden (cfaed) & Department of Chemistry and Food Chemistry, Technische Universität Dresden, Dresden, 01062, Germany; Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden Center for Computational Materials Science & Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, 01062, Germany; Max Planck Institute for Polymer Research, Mainz, 55128, Germany; Dresden Center for Nanoanalysis (DCN), Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={On-chip micro-supercapacitors (MSCs) are important Si-compatible power-source backups for miniaturized electronics. Despite their tremendous advantages, current on-chip MSCs require harsh processing conditions and typically perform like resistors when filtering ripples from alternating current (AC). Herein, we demonstrated a facile layer-by-layer method towards on-chip MSCs based on an azulene-bridged coordination polymer framework (PiCBA). Owing to the good carrier mobility (5×10−3 cm2 V−1 s−1) of PiCBA, the permanent dipole moment of azulene skeleton, and ultralow band gap of PiCBA, the fabricated MSCs delivered high specific capacitances of up to 34.1 F cm−3 at 50 mV s−1 and a high volumetric power density of 1323 W cm−3. Most importantly, such MCSs exhibited AC line-filtering performance (−73° at 120 Hz) with a short resistance–capacitance constant of circa 0.83 ms. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim},
      author_keywords={AC line-filtering; azulene; coordination polymers; layer-by-layer methods; micro-supercapacitors},
      document_type={Article},
      source={Scopus},
      }

  • A Stable Saddle-Shaped Polycyclic Hydrocarbon with an Open-Shell Singlet Ground State
    • J. Ma, J. Liu, M. Baumgarten, Y. Fu, Y. -Z. Tan, K. S. Schellhammer, F. Ortmann, G. Cuniberti, H. Komber, R. Berger, K. Müllen, X. Feng
    • Angewandte Chemie – International Edition 56, 3280-3284 (2017)
    • DOI   Abstract  

      Diindeno-fused bischrysene, a new diindeno-based polycyclic hydrocarbon (PH), was synthesized and characterized. It was elucidated in detailed experimental and theoretical studies that this cyclopenta-fused PH possesses an open-shell singlet biradical structure in the ground state and exhibits high stability under ambient conditions (t1/2=39 days). The crystal structure unambiguously shows a novel saddle-shaped π-conjugated carbon skeleton due to the steric hindrance of the central cove-edged bischrysene unit. UV/Vis spectral measurements revealed that the title molecule has a very narrow optical energy gap of 0.92 eV, which is consistent with the electrochemical analysis and further supported by density functional theory (DFT) calculations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

      @ARTICLE{Ma20173280,
      author={Ma, J. and Liu, J. and Baumgarten, M. and Fu, Y. and Tan, Y.-Z. and Schellhammer, K.S. and Ortmann, F. and Cuniberti, G. and Komber, H. and Berger, R. and Müllen, K. and Feng, X.},
      title={A Stable Saddle-Shaped Polycyclic Hydrocarbon with an Open-Shell Singlet Ground State},
      journal={Angewandte Chemie - International Edition},
      year={2017},
      volume={56},
      number={12},
      pages={3280-3284},
      doi={10.1002/anie.201611689},
      note={cited By 50},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013669821&doi=10.1002%2fanie.201611689&partnerID=40&md5=3988f5c7ded621ea0ca1ee5d09408f46},
      affiliation={Center for Advancing Electronics Dresden (cfaed), Department of Chemistry and Food Chemistry, Technische Universität Dresden, Dresden, 01062, Germany; Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany; State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China; Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; Leibniz-Institut für Polymerforschung Dresden e. V., Hohe Strasse 6, Dresden, 01069, Germany},
      abstract={Diindeno-fused bischrysene, a new diindeno-based polycyclic hydrocarbon (PH), was synthesized and characterized. It was elucidated in detailed experimental and theoretical studies that this cyclopenta-fused PH possesses an open-shell singlet biradical structure in the ground state and exhibits high stability under ambient conditions (t1/2=39 days). The crystal structure unambiguously shows a novel saddle-shaped π-conjugated carbon skeleton due to the steric hindrance of the central cove-edged bischrysene unit. UV/Vis spectral measurements revealed that the title molecule has a very narrow optical energy gap of 0.92 eV, which is consistent with the electrochemical analysis and further supported by density functional theory (DFT) calculations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim},
      author_keywords={aromaticity; biradicals; electronic structure; polycyclic hydrocarbons; saddle conformation},
      document_type={Article},
      source={Scopus},
      }

  • Simulation of self-piercing rivetting processes in fibre reinforced polymers: Material modelling and parameter identification
    • F. Hirsch, S. Müller, M. Machens, R. Staschko, N. Fuchs, M. Kästner
    • Journal of Materials Processing Technology 241, 164-177 (2017)
    • DOI   Abstract  

      This paper addresses the numerical simulation of self-piercing rivetting processes to join fibre reinforced polymers and sheet metals. Special emphasis is placed on the modelling of the deformation and failure behaviour of the composite material. Different from the simulation of rivetting processes in metals, which requires the modelling of large plastic deformations, the mechanical response of composites is typically governed by intra- and interlaminar damage phenomena. Depending on the polymeric matrix, viscoelastic effects can interfere particularly with the long-term behaviour of the joint. We propose a systematic approach to the modelling of composite laminates, discuss limitations of the used model, and present details of parameter identification. Homogenisation techniques are applied to predict the mechanical behaviour of the composite in terms of effective anisotropic elastic and viscoelastic material properties. In combination with a continuum damage approach this model represents the deformation and failure behaviour of individual laminae. Cohesive zones enable the modelling of delamination processes. The parameters of the latter models are identified from experiments. The defined material model for the composite is eventually utilised in the simulation of an exemplary self-piercing rivetting process. © 2016 Elsevier B.V.

      @ARTICLE{Hirsch2017164,
      author={Hirsch, F. and Müller, S. and Machens, M. and Staschko, R. and Fuchs, N. and Kästner, M.},
      title={Simulation of self-piercing rivetting processes in fibre reinforced polymers: Material modelling and parameter identification},
      journal={Journal of Materials Processing Technology},
      year={2017},
      volume={241},
      pages={164-177},
      doi={10.1016/j.jmatprotec.2016.10.010},
      note={cited By 20},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84997523659&doi=10.1016%2fj.jmatprotec.2016.10.010&partnerID=40&md5=83164af656890f6a77d860612a9635b5},
      affiliation={TU Dresden, Institute of Solid Mechanics, Dresden, D-01062, Germany; Fraunhofer Application Center Large Structures in Production Technology AGP, Rostock, D-18059, Germany; University of Rostock, Chair of Manufacturing Engineering, Rostock, D-18059, Germany; TU Dresden, Dresden Center for Computational Materials Science, Dresden, D-01062, Germany},
      abstract={This paper addresses the numerical simulation of self-piercing rivetting processes to join fibre reinforced polymers and sheet metals. Special emphasis is placed on the modelling of the deformation and failure behaviour of the composite material. Different from the simulation of rivetting processes in metals, which requires the modelling of large plastic deformations, the mechanical response of composites is typically governed by intra- and interlaminar damage phenomena. Depending on the polymeric matrix, viscoelastic effects can interfere particularly with the long-term behaviour of the joint. We propose a systematic approach to the modelling of composite laminates, discuss limitations of the used model, and present details of parameter identification. Homogenisation techniques are applied to predict the mechanical behaviour of the composite in terms of effective anisotropic elastic and viscoelastic material properties. In combination with a continuum damage approach this model represents the deformation and failure behaviour of individual laminae. Cohesive zones enable the modelling of delamination processes. The parameters of the latter models are identified from experiments. The defined material model for the composite is eventually utilised in the simulation of an exemplary self-piercing rivetting process. © 2016 Elsevier B.V.},
      author_keywords={Cohesive zone; Damage; Fibre-reinforced composites; Homogenisation; Self-piercing rivetting},
      document_type={Article},
      source={Scopus},
      }

  • Competence-Based, Research-Related Lab Courses for Materials Modeling: The Case of Organic Photovoltaics
    • K. S. Schellhammer, G. Cuniberti
    • Journal of Chemical Education 94, 190-194 (2017)
    • DOI   Abstract  

      We are hereby presenting a didactic concept for an advanced lab course that focuses on the design of donor materials for organic solar cells. Its research-related and competence-based approach qualifies the students to independently and creatively apply computational methods and to profoundly and critically discuss the results obtained. The high degree of multidisciplinarity and the diversity of both the field of materials modeling and the students are considered within a modularized structure that allows the students to advance according to their individual abilities and interests. On the basis of our experience, through a hands-on format, it is possible to effectively capture the students’ intrinsic interest in this research field and prepare them for their future work in academia and industry. © 2017 The American Chemical Society and Division of Chemical Education, Inc.

      @ARTICLE{Schellhammer2017190,
      author={Schellhammer, K.S. and Cuniberti, G.},
      title={Competence-Based, Research-Related Lab Courses for Materials Modeling: The Case of Organic Photovoltaics},
      journal={Journal of Chemical Education},
      year={2017},
      volume={94},
      number={2},
      pages={190-194},
      doi={10.1021/acs.jchemed.6b00499},
      note={cited By 4},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012912811&doi=10.1021%2facs.jchemed.6b00499&partnerID=40&md5=b5f00c76c8f32164adc44ec20d128fb5},
      affiliation={Institute for Materials Science, Dresden Center for Computational Materials Science, Max Bergmann Center of Biomaterials, Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={We are hereby presenting a didactic concept for an advanced lab course that focuses on the design of donor materials for organic solar cells. Its research-related and competence-based approach qualifies the students to independently and creatively apply computational methods and to profoundly and critically discuss the results obtained. The high degree of multidisciplinarity and the diversity of both the field of materials modeling and the students are considered within a modularized structure that allows the students to advance according to their individual abilities and interests. On the basis of our experience, through a hands-on format, it is possible to effectively capture the students’ intrinsic interest in this research field and prepare them for their future work in academia and industry. © 2017 The American Chemical Society and Division of Chemical Education, Inc.},
      author_keywords={Applications of Chemistry; Collaborative/Cooperative Learning; Computer-Based Learning; Graduate Education/Research; Inquiry-Based/Discovery Learning; Interdisciplinary/Multidisciplinary; Molecular Modeling; Organic Chemistry; Physical Chemistry},
      document_type={Article},
      source={Scopus},
      }

  • Absorption tails of donor:C60 blends provide insight into thermally activated charge-transfer processes and polaron relaxation
    • K. Vandewal, J. Benduhn, K. S. Schellhammer, T. Vangerven, J. E. Rückert, F. Piersimoni, R. Scholz, O. Zeika, Y. Fan, S. Barlow, D. Neher, S. R. Marder, J. Manca, D. Spoltore, G. Cuniberti, F. Ortmann
    • Journal of the American Chemical Society 139, 1699-1704 (2017)
    • DOI   Abstract  

      In disordered organic semiconductors, the transfer of a rather localized charge carrier from one site to another triggers a deformation of the molecular structure quantified by the intramolecular relaxation energy. A similar structural relaxation occurs upon population of intermolecular charge-transfer (CT) states formed at organic electron donor (D)-acceptor (A) interfaces. Weak CT absorption bands for D-A complexes occur at photon energies below the optical gaps of both the donors and the C60 acceptor as a result of optical transitions from the neutral ground state to the ionic CT state. In this work, we show that temperature-activated intramolecular vibrations of the ground state play a major role in determining the line shape of such CT absorption bands. This allows us to extract values for the relaxation energy related to the geometry change from neutral to ionic CT complexes. Experimental values for the relaxation energies of 20 D:C60 CT complexes correlate with values calculated within density functional theory. These results provide an experimental method for determining the polaron relaxation energy in solid-state organic D-A blends and show the importance of a reduced relaxation energy, which we introduce to characterize thermally activated CT processes. (Figure Presented). © 2017 American Chemical Society.

      @ARTICLE{Vandewal20171699,
      author={Vandewal, K. and Benduhn, J. and Schellhammer, K.S. and Vangerven, T. and Rückert, J.E. and Piersimoni, F. and Scholz, R. and Zeika, O. and Fan, Y. and Barlow, S. and Neher, D. and Marder, S.R. and Manca, J. and Spoltore, D. and Cuniberti, G. and Ortmann, F.},
      title={Absorption tails of donor:C60 blends provide insight into thermally activated charge-transfer processes and polaron relaxation},
      journal={Journal of the American Chemical Society},
      year={2017},
      volume={139},
      number={4},
      pages={1699-1704},
      doi={10.1021/jacs.6b12857},
      note={cited By 39},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011056282&doi=10.1021%2fjacs.6b12857&partnerID=40&md5=d0baf6325aec0efd984cca4d248d6b00},
      affiliation={Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP), Institute for Applied Physics, Technische Universität Dresden, Dresden, 01062, Germany; Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, Dresden, 01062, Germany; Material Physics Division, Institute for Materials Research (IMO-IMOMEC), Hasselt University, Universitaire Campus, Wetenschapspark 1, Diepenbeek, B-3590, Belgium; Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Straße 24-25, Potsdam, 14476, Germany; Center for Organic Photonics and Electronics, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, United States; X-LaB, Hasselt University, Universitaire Campus, Agoralaan 1, Diepenbeek, B-3590, Belgium; School of Chemistry and Chemical Engineering, Southeast University, Nanjing, Jiangsu 211189, China},
      abstract={In disordered organic semiconductors, the transfer of a rather localized charge carrier from one site to another triggers a deformation of the molecular structure quantified by the intramolecular relaxation energy. A similar structural relaxation occurs upon population of intermolecular charge-transfer (CT) states formed at organic electron donor (D)-acceptor (A) interfaces. Weak CT absorption bands for D-A complexes occur at photon energies below the optical gaps of both the donors and the C60 acceptor as a result of optical transitions from the neutral ground state to the ionic CT state. In this work, we show that temperature-activated intramolecular vibrations of the ground state play a major role in determining the line shape of such CT absorption bands. This allows us to extract values for the relaxation energy related to the geometry change from neutral to ionic CT complexes. Experimental values for the relaxation energies of 20 D:C60 CT complexes correlate with values calculated within density functional theory. These results provide an experimental method for determining the polaron relaxation energy in solid-state organic D-A blends and show the importance of a reduced relaxation energy, which we introduce to characterize thermally activated CT processes. (Figure Presented). © 2017 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Elastic and piezoresistive properties of nickel carbides from first principles
    • J. Kelling, P. Zahn, J. Schuster, S. Gemming
    • Physical Review B 95, 024113 (2017)
    • DOI   Abstract  

      The nickel-carbon system has received increased attention over the past years due to the relevance of nickel as a catalyst for carbon nanotube and graphene growth, where nickel carbide intermediates may be involved or carbide interface layers form in the end. Nickel-carbon composite thin films comprising Ni3C are especially interesting in mechanical sensing applications. Due to the metastability of nickel carbides, formation conditions and the coupling between mechanical and electrical properties are not yet well understood. Using first-principles electronic structure methods, we calculated the elastic properties of Ni3C,Ni2C, and NiC, as well as changes in electronic properties under mechanical strain. We observe that the electronic density of states around the Fermi level does not change under the considered strains of up to 1%, which correspond to stresses up to 3GPa. Relative changes in conductivity of Ni3C range up to maximum values of about 10%. © 2017 American Physical Society.

      @ARTICLE{Kelling2017,
      author={Kelling, J. and Zahn, P. and Schuster, J. and Gemming, S.},
      title={Elastic and piezoresistive properties of nickel carbides from first principles},
      journal={Physical Review B},
      year={2017},
      volume={95},
      number={2},
      doi={10.1103/PhysRevB.95.024113},
      art_number={024113},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012299139&doi=10.1103%2fPhysRevB.95.024113&partnerID=40&md5=46d585b2b8e53c944a531804888e9327},
      affiliation={Helmholtz-Zentrum Dresden - Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstraße 400, Dresden, 01328, Germany; Institute of Physics, TU Chemnitz, Chemnitz, 09107, Germany; Helmholtz-Zentrum Dresden - Rossendorf, International Helmholtz Research School for Nanoelectronic Networks (IHRS NanoNet), Bautzner Landstraße 400, Dresden, 01328, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Fraunhofer Institute for Electronic Nano Systems (ENAS), Technologie-Campus 3, Chemnitz, 09126, Germany; Center for Advancing Electronics Dresden (Cfaed), TU Dresden, Dresden, 01062, Germany},
      abstract={The nickel-carbon system has received increased attention over the past years due to the relevance of nickel as a catalyst for carbon nanotube and graphene growth, where nickel carbide intermediates may be involved or carbide interface layers form in the end. Nickel-carbon composite thin films comprising Ni3C are especially interesting in mechanical sensing applications. Due to the metastability of nickel carbides, formation conditions and the coupling between mechanical and electrical properties are not yet well understood. Using first-principles electronic structure methods, we calculated the elastic properties of Ni3C,Ni2C, and NiC, as well as changes in electronic properties under mechanical strain. We observe that the electronic density of states around the Fermi level does not change under the considered strains of up to 1%, which correspond to stresses up to 3GPa. Relative changes in conductivity of Ni3C range up to maximum values of about 10%. © 2017 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Charge carrier mobility in one-dimensional aligned π-stacks of conjugated small molecules with a benzothiadiazole central unit
    • D. Raychev, O. Guskova
    • Physical Chemistry Chemical Physics 19, 8330-8339 (2017)
    • DOI   Abstract  

      A theoretical study is applied to gain insight into the microscopic electron and hole transport in benzothiadiazole-cored molecular semiconductors either with furan or thiophene flanks arranged in π-stacks. For the characterization of the energetics of the reduction and oxidation processes and their impact on the molecular geometry, the internal reorganization energy is defined for isolated molecules in the gas phase. The outer-shell reorganization energy is evaluated within the frequency-resolved cavity model and as an electrostatic contribution within the polarizable continuum model. The intermolecular electronic coupling interaction for the Marcus charge hopping is calculated using the energy splitting in dimer method, the generalized Mulliken-Hush approach and the fragment charge difference scheme. In order to probe the relation between the charge hopping rate/charge carrier mobility and the molecular organization within the π-stacks, different stacking modes are investigated: (i) dimers with a perfect registry, i.e. segregated stacking motif, when molecules are placed face-to-face, and (ii) dimers forming slipped cofacial orientations with longitudinal and transverse shifts, i.e. mixed stacking motif. Besides, the effects of molecular planarity and rigidity, influencing internal molecular relaxation upon charging, the effects of non-covalent interactions within stacks and the heteroatom replacement on the charge carrier mobility are studied. The results obtained in the simulations of one-dimensional aligned π-stacks of molecular semiconductors are compared with available experimental data for small conjugated benzothiadiazole-cored molecules with thiophene flanks and benzothiadiazole-quaterthiophene-based copolymers. © the Owner Societies 2017.

      @ARTICLE{Raychev20178330,
      author={Raychev, D. and Guskova, O.},
      title={Charge carrier mobility in one-dimensional aligned π-stacks of conjugated small molecules with a benzothiadiazole central unit},
      journal={Physical Chemistry Chemical Physics},
      year={2017},
      volume={19},
      number={12},
      pages={8330-8339},
      doi={10.1039/c7cp00798a},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019019229&doi=10.1039%2fc7cp00798a&partnerID=40&md5=e0b94fe64d16b0a839ee5238d99bc65a},
      affiliation={Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden (TUD), Dresden, D-01062, Germany; Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, D-01069, Germany},
      abstract={A theoretical study is applied to gain insight into the microscopic electron and hole transport in benzothiadiazole-cored molecular semiconductors either with furan or thiophene flanks arranged in π-stacks. For the characterization of the energetics of the reduction and oxidation processes and their impact on the molecular geometry, the internal reorganization energy is defined for isolated molecules in the gas phase. The outer-shell reorganization energy is evaluated within the frequency-resolved cavity model and as an electrostatic contribution within the polarizable continuum model. The intermolecular electronic coupling interaction for the Marcus charge hopping is calculated using the energy splitting in dimer method, the generalized Mulliken-Hush approach and the fragment charge difference scheme. In order to probe the relation between the charge hopping rate/charge carrier mobility and the molecular organization within the π-stacks, different stacking modes are investigated: (i) dimers with a perfect registry, i.e. segregated stacking motif, when molecules are placed face-to-face, and (ii) dimers forming slipped cofacial orientations with longitudinal and transverse shifts, i.e. mixed stacking motif. Besides, the effects of molecular planarity and rigidity, influencing internal molecular relaxation upon charging, the effects of non-covalent interactions within stacks and the heteroatom replacement on the charge carrier mobility are studied. The results obtained in the simulations of one-dimensional aligned π-stacks of molecular semiconductors are compared with available experimental data for small conjugated benzothiadiazole-cored molecules with thiophene flanks and benzothiadiazole-quaterthiophene-based copolymers. © the Owner Societies 2017.},
      document_type={Article},
      source={Scopus},
      }

  • Copper electroplating with polyethylene glycol: I. An alternative hysteresis model without additive consumption
    • H. Yang, A. Dianat, M. Bobeth, G. Cuniberti
    • Journal of the Electrochemical Society 164, D196-D203 (2017)
    • DOI   Abstract  

      Additives play an important role in electrochemical deposition and understanding their working mechanism is a great challenge. In cyclic voltammetrymeasurements of copper deposition, hysteresis is ubiquitously observed. Correct prediction of hysteresis behavior is an important test for deposition models. In previous models, including poly(ethylene glycol) (PEG) and chloride ions as additives, a common assumption to explain the hysteresis is the consumption of additives during copper deposition. However, second-ion mass spectrometry measurements often detected comparatively low levels of impurities in deposits. Therefore, we propose here an alternative mechanism for explaining hysteresis curves without invoking additive consumption. Essential ingredients of our models are: (i) a strongly nonlinear dependence of the maximal possible PEG coverage on the chloride coverage on the copper surface, (ii) a nonlinear dependence of the deposition current on the PEG surface coverage, and (iii) an additional activation of the desorption of additives with increasing copper deposition current. We demonstrate that our model reproduces characteristic features of cyclic voltammograms measured under vastly different conditions and exhibiting pronounced hysteresis. Furthermore, simulations are compared well to PEG adsorption/desorption experiments with varying additive concentrations. The proposed model may serve to describe deposition situations with negligible additive consumption. © 2017 The Electrochemical Society. All rights reserved.

      @ARTICLE{Yang2017D196,
      author={Yang, H. and Dianat, A. and Bobeth, M. and Cuniberti, G.},
      title={Copper electroplating with polyethylene glycol: I. An alternative hysteresis model without additive consumption},
      journal={Journal of the Electrochemical Society},
      year={2017},
      volume={164},
      number={4},
      pages={D196-D203},
      doi={10.1149/2.1051704jes},
      note={cited By 14},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020654816&doi=10.1149%2f2.1051704jes&partnerID=40&md5=8f0ec19d28b9c49937571bc48cdb9e64},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden (CfAED), Dresden, 01062, Germany},
      abstract={Additives play an important role in electrochemical deposition and understanding their working mechanism is a great challenge. In cyclic voltammetrymeasurements of copper deposition, hysteresis is ubiquitously observed. Correct prediction of hysteresis behavior is an important test for deposition models. In previous models, including poly(ethylene glycol) (PEG) and chloride ions as additives, a common assumption to explain the hysteresis is the consumption of additives during copper deposition. However, second-ion mass spectrometry measurements often detected comparatively low levels of impurities in deposits. Therefore, we propose here an alternative mechanism for explaining hysteresis curves without invoking additive consumption. Essential ingredients of our models are: (i) a strongly nonlinear dependence of the maximal possible PEG coverage on the chloride coverage on the copper surface, (ii) a nonlinear dependence of the deposition current on the PEG surface coverage, and (iii) an additional activation of the desorption of additives with increasing copper deposition current. We demonstrate that our model reproduces characteristic features of cyclic voltammograms measured under vastly different conditions and exhibiting pronounced hysteresis. Furthermore, simulations are compared well to PEG adsorption/desorption experiments with varying additive concentrations. The proposed model may serve to describe deposition situations with negligible additive consumption. © 2017 The Electrochemical Society. All rights reserved.},
      document_type={Article},
      source={Scopus},
      }

  • Spin-orbit coupling in nearly metallic chiral carbon nanotubes: A density-functional based study
    • V. V. Maslyuk, R. Gutierrez, G. Cuniberti
    • Physical Chemistry Chemical Physics 19, 8848-8853 (2017)
    • DOI   Abstract  

      Spin-orbit interaction in carbon nanotubes has been under debate for several years and a variety of theoretical calculations and experimental results have been published. Here, we present an accurate implementation of spin-orbit interactions in a density-functional theory framework including both core and valence orbital contributions, thus using the full potential of the system. We find that the spin-splitting of the frontier bands of armchair nanotubes is of the order of several μeV and does not strongly depend on the diameter of the nanotube. We also provide a systematic analysis of the band splitting in chiral nanotubes as a function of the diameter and the chiral angle. Very good agreement with previous theoretical studies and experimental results is overall found. In particular, our approach can be of great relevance in view of the recently discovered chirality-induced spin selectivity, since it allows us to include not only atomic contributions to the spin-orbit interaction, but more importantly, global contributions to the potential arising from the geometric structure (topology) of the system. Our methodology can thus encode effects such as helical symmetry in a straightforward way. © 2017 the Owner Societies.

      @ARTICLE{Maslyuk20178848,
      author={Maslyuk, V.V. and Gutierrez, R. and Cuniberti, G.},
      title={Spin-orbit coupling in nearly metallic chiral carbon nanotubes: A density-functional based study},
      journal={Physical Chemistry Chemical Physics},
      year={2017},
      volume={19},
      number={13},
      pages={8848-8853},
      doi={10.1039/c7cp00059f},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019377663&doi=10.1039%2fc7cp00059f&partnerID=40&md5=9dace006c5037a789fb7a2f1e3486a3f},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Spin-orbit interaction in carbon nanotubes has been under debate for several years and a variety of theoretical calculations and experimental results have been published. Here, we present an accurate implementation of spin-orbit interactions in a density-functional theory framework including both core and valence orbital contributions, thus using the full potential of the system. We find that the spin-splitting of the frontier bands of armchair nanotubes is of the order of several μeV and does not strongly depend on the diameter of the nanotube. We also provide a systematic analysis of the band splitting in chiral nanotubes as a function of the diameter and the chiral angle. Very good agreement with previous theoretical studies and experimental results is overall found. In particular, our approach can be of great relevance in view of the recently discovered chirality-induced spin selectivity, since it allows us to include not only atomic contributions to the spin-orbit interaction, but more importantly, global contributions to the potential arising from the geometric structure (topology) of the system. Our methodology can thus encode effects such as helical symmetry in a straightforward way. © 2017 the Owner Societies.},
      document_type={Article},
      source={Scopus},
      }

  • Morphological Evolution of Pit-Patterned Si(001) Substrates Driven by Surface-Energy Reduction
    • M. Salvalaglio, R. Backofen, A. Voigt, F. Montalenti
    • Nanoscale Research Letters 12, 554 (2017)
    • DOI   Abstract  

      Lateral ordering of heteroepitaxial islands can be conveniently achieved by suitable pit-patterning of the substrate prior to deposition. Controlling shape, orientation, and size of the pits is not trivial as, being metastable, they can significantly evolve during deposition/annealing. In this paper, we exploit a continuum model to explore the typical metastable pit morphologies that can be expected on Si(001), depending on the initial depth/shape. Evolution is predicted using a surface-diffusion model, formulated in a phase-field framework, and tackling surface-energy anisotropy. Results are shown to nicely reproduce typical metastable shapes reported in the literature. Moreover, long time scale evolutions of pit profiles with different depths are found to follow a similar kinetic pathway. The model is also exploited to treat the case of heteroepitaxial growth involving two materials characterized by different facets in their equilibrium Wulff’s shape. This can lead to significant changes in morphologies, such as a rotation of the pit during deposition as evidenced in Ge/Si experiments. © 2017, The Author(s).

      @ARTICLE{Salvalaglio2017,
      author={Salvalaglio, M. and Backofen, R. and Voigt, A. and Montalenti, F.},
      title={Morphological Evolution of Pit-Patterned Si(001) Substrates Driven by Surface-Energy Reduction},
      journal={Nanoscale Research Letters},
      year={2017},
      volume={12},
      doi={10.1186/s11671-017-2320-5},
      art_number={554},
      note={cited By 21},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85030640070&doi=10.1186%2fs11671-017-2320-5&partnerID=40&md5=f0ad68c5615e3d64fa427f2521f93a9d},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; IHP, Im Technologiepark 25, Frankfurt (Oder), 15236, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany; L-NESS and Department of Materials Science, Università di Milano-Bicocca, via R. Cozzi 55, Milano, I-20126, Italy},
      abstract={Lateral ordering of heteroepitaxial islands can be conveniently achieved by suitable pit-patterning of the substrate prior to deposition. Controlling shape, orientation, and size of the pits is not trivial as, being metastable, they can significantly evolve during deposition/annealing. In this paper, we exploit a continuum model to explore the typical metastable pit morphologies that can be expected on Si(001), depending on the initial depth/shape. Evolution is predicted using a surface-diffusion model, formulated in a phase-field framework, and tackling surface-energy anisotropy. Results are shown to nicely reproduce typical metastable shapes reported in the literature. Moreover, long time scale evolutions of pit profiles with different depths are found to follow a similar kinetic pathway. The model is also exploited to treat the case of heteroepitaxial growth involving two materials characterized by different facets in their equilibrium Wulff’s shape. This can lead to significant changes in morphologies, such as a rotation of the pit during deposition as evidenced in Ge/Si experiments. © 2017, The Author(s).},
      author_keywords={Epitaxy; Phase field; Silicon; Surface diffusion; Surface energy},
      document_type={Article},
      source={Scopus},
      }

  • Conformational and electronic properties of small benzothiadiazole-cored oligomers with aryl flanking units: Thiophene versus Furan
    • D. Raychev, O. Guskova, G. Seifert, J. -U. Sommer
    • Computational Materials Science 126, 287-298 (2017)
    • DOI   Abstract  

      Symmetrical benzothiadiazole-cored (BTZ) oligomers with aromatic flanks are widely used in experiments as structural blocks for organic electronic materials. Along with chemical composition, the molecular conformation plays a crucial role in crystal packing/self-assembly of these building blocks in thin films. In this study, we perform an extensive theoretical comparison of conformational preferences, electronic and optical properties of small π-conjugated molecules having BTZ central unit symmetrically decorated with thiophene (Th) or furan (Fu) rings using DFT calculations. In addition to the conformational screening of small molecules, the torsion potentials of the internal rotation and the energetics of weak intramolecular S⋯N, O⋯N, O⋯H and N⋯H nonbonded interactions stabilizing certain conformations are evaluated. The conformational properties of –[BTZ-Fu]n– and –[BTZ-Th]n– chains are predicted applying the hindered rotation model. Our calculation shows that substitution of one atom, here sulphur by oxygen, leads to huge stiffening of the resulting polymer as estimated by the Kuhn length based on the rotational isomeric model. On the other hand, the calculation of the band gaps and the UV–vis spectra shows that the electronic and optical properties of both compounds are almost identical. This offers the possibility to decouple the intramolecular electronic properties from the intermolecular arrangement and the morphology of the materials since the latter properties are sensitive to the local stiffness of oligomers and polymers. © 2016 Elsevier B.V.

      @ARTICLE{Raychev2017287,
      author={Raychev, D. and Guskova, O. and Seifert, G. and Sommer, J.-U.},
      title={Conformational and electronic properties of small benzothiadiazole-cored oligomers with aryl flanking units: Thiophene versus Furan},
      journal={Computational Materials Science},
      year={2017},
      volume={126},
      pages={287-298},
      doi={10.1016/j.commatsci.2016.09.044},
      note={cited By 15},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992458915&doi=10.1016%2fj.commatsci.2016.09.044&partnerID=40&md5=91fadcc578c3e424963b45ad5d0f2a8c},
      affiliation={Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, D-01062, Germany; Institute Theory of Polymers, Leibniz-Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, D-01069, Germany; Theoretical Chemistry, TU Dresden, Dresden, D-01062, Germany; Institute of Theoretical Physics, TU Dresden, Zellescher Weg 17, Dresden, D-01069, Germany},
      abstract={Symmetrical benzothiadiazole-cored (BTZ) oligomers with aromatic flanks are widely used in experiments as structural blocks for organic electronic materials. Along with chemical composition, the molecular conformation plays a crucial role in crystal packing/self-assembly of these building blocks in thin films. In this study, we perform an extensive theoretical comparison of conformational preferences, electronic and optical properties of small π-conjugated molecules having BTZ central unit symmetrically decorated with thiophene (Th) or furan (Fu) rings using DFT calculations. In addition to the conformational screening of small molecules, the torsion potentials of the internal rotation and the energetics of weak intramolecular S⋯N, O⋯N, O⋯H and N⋯H nonbonded interactions stabilizing certain conformations are evaluated. The conformational properties of –[BTZ-Fu]n– and –[BTZ-Th]n– chains are predicted applying the hindered rotation model. Our calculation shows that substitution of one atom, here sulphur by oxygen, leads to huge stiffening of the resulting polymer as estimated by the Kuhn length based on the rotational isomeric model. On the other hand, the calculation of the band gaps and the UV–vis spectra shows that the electronic and optical properties of both compounds are almost identical. This offers the possibility to decouple the intramolecular electronic properties from the intermolecular arrangement and the morphology of the materials since the latter properties are sensitive to the local stiffness of oligomers and polymers. © 2016 Elsevier B.V.},
      author_keywords={Benzothiadiazole; Conformer; DFT; Kuhn segment; Noncovalent interactions; Ribbon-like polymer},
      document_type={Article},
      source={Scopus},
      }

  • Coherent spin dynamics in a helical arrangement of molecular dipoles
    • E. Díaz, R. Gutiérrez, C. Gaul, G. Cuniberti, F. Domínguez-Adame
    • AIMS Materials Science 4, 1052-1061 (2017)
    • DOI   Abstract  

      Experiments on electron transport through helical molecules have demonstrated the appearance of high spin selectivity, in spite of the rather weak spin-orbit coupling in organic compounds. Theoretical models usually rely on different mechanisms to explain these experiments, such as large spin-orbit coupling, quantum dephasing, the role of metallic contacts, or the interplay between a helicity-induced spin-orbit coupling and a strong dipole electric field. In this work we consider the coherent electron dynamics in the electric field created by the helical arrangement of dipoles of the molecule backbone, giving rise to an effective spin-orbit coupling. We calculate the spin projection onto the helical axis as a figure of merit for the assessment of the spin dynamics in a very long helical molecule. We prove that the spin projection reaches a steady state regime after a short transient. We compare its asymptotic value for different initial conditions, aiming to better understand the origin of the spin selectivity found in experiments. © 2017, Francisco Domínguez-Adame, et al.

      @ARTICLE{Díaz20171052,
      author={Díaz, E. and Gutiérrez, R. and Gaul, C. and Cuniberti, G. and Domínguez-Adame, F.},
      title={Coherent spin dynamics in a helical arrangement of molecular dipoles},
      journal={AIMS Materials Science},
      year={2017},
      volume={4},
      number={5},
      pages={1052-1061},
      doi={10.3934/matersci.2017.5.1052},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85037104056&doi=10.3934%2fmatersci.2017.5.1052&partnerID=40&md5=28e78b12f52c5aaac3d4face070a9a28},
      affiliation={GISC, Departamento de Física de Materiales, Universidad Complutense, Madrid, E-28040, Spain; Institute for Materials Science, Dresden University of Technology, Dresden, 01062, Germany; Cognitec Systems GmbH, Großenhainer Str. 101, Dresden, 01127, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Experiments on electron transport through helical molecules have demonstrated the appearance of high spin selectivity, in spite of the rather weak spin-orbit coupling in organic compounds. Theoretical models usually rely on different mechanisms to explain these experiments, such as large spin-orbit coupling, quantum dephasing, the role of metallic contacts, or the interplay between a helicity-induced spin-orbit coupling and a strong dipole electric field. In this work we consider the coherent electron dynamics in the electric field created by the helical arrangement of dipoles of the molecule backbone, giving rise to an effective spin-orbit coupling. We calculate the spin projection onto the helical axis as a figure of merit for the assessment of the spin dynamics in a very long helical molecule. We prove that the spin projection reaches a steady state regime after a short transient. We compare its asymptotic value for different initial conditions, aiming to better understand the origin of the spin selectivity found in experiments. © 2017, Francisco Domínguez-Adame, et al.},
      author_keywords={Helical molecules; Nanoscale materials; Spin polarized transport; Spin sensitivity; Spin-orbit coupling},
      document_type={Article},
      source={Scopus},
      }

  • Tuning quantum electron and phonon transport in two-dimensional materials by strain engineering: A Green’s function based study
    • L. M. Sandonas, R. Gutierrez, A. Pecchia, G. Seifert, G. Cuniberti
    • Physical Chemistry Chemical Physics 19, 1487-1495 (2017)
    • DOI   Abstract  

      Novel two-dimensional (2D) materials show unusual physical properties which combined with strain engineering open up the possibility of new potential device applications in nanoelectronics. In particular, transport properties have been found to be very sensitive to applied strain. In the present work, using a density-functional based tight-binding (DFTB) method in combination with Green’s function (GF) approaches, we address the effect of strain engineering of the transport setup (contact-device(scattering)-contact regions) on the electron and phonon transport properties of two-dimensional materials, focusing on hexagonal boron-nitride (hBN), phosphorene, and MoS2 monolayers. Considering unstretched contact regions, we show that the electronic bandgap displays an anomalous behavior and the thermal conductance continuously decreases after increasing the strain level in the scattering region. However, when the whole system (contact and device regions) is homogeneously strained, the bandgap for hBN and MoS2 monolayers decreases, while for phosphorene it first increases and then tends to zero with larger strain levels. Additionally, the thermal conductance shows specific strain dependence for each of the studied 2D materials. These effects can be tuned by modifying the strain level in the stretched contact regions. © 2017 the Owner Societies.

      @ARTICLE{Sandonas20171487,
      author={Sandonas, L.M. and Gutierrez, R. and Pecchia, A. and Seifert, G. and Cuniberti, G.},
      title={Tuning quantum electron and phonon transport in two-dimensional materials by strain engineering: A Green's function based study},
      journal={Physical Chemistry Chemical Physics},
      year={2017},
      volume={19},
      number={2},
      pages={1487-1495},
      doi={10.1039/c6cp06621f},
      note={cited By 14},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027273654&doi=10.1039%2fc6cp06621f&partnerID=40&md5=8f59b06200c350c829086326bbb103f0},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany; Consiglio Nazionale Delle Ricerche, ISMN, Via Salaria km 29.6, Monterotondo Rome, 00017, Italy; Institut für Physikalische Chemie und Elektrochemie, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Novel two-dimensional (2D) materials show unusual physical properties which combined with strain engineering open up the possibility of new potential device applications in nanoelectronics. In particular, transport properties have been found to be very sensitive to applied strain. In the present work, using a density-functional based tight-binding (DFTB) method in combination with Green's function (GF) approaches, we address the effect of strain engineering of the transport setup (contact-device(scattering)-contact regions) on the electron and phonon transport properties of two-dimensional materials, focusing on hexagonal boron-nitride (hBN), phosphorene, and MoS2 monolayers. Considering unstretched contact regions, we show that the electronic bandgap displays an anomalous behavior and the thermal conductance continuously decreases after increasing the strain level in the scattering region. However, when the whole system (contact and device regions) is homogeneously strained, the bandgap for hBN and MoS2 monolayers decreases, while for phosphorene it first increases and then tends to zero with larger strain levels. Additionally, the thermal conductance shows specific strain dependence for each of the studied 2D materials. These effects can be tuned by modifying the strain level in the stretched contact regions. © 2017 the Owner Societies.},
      document_type={Article},
      source={Scopus},
      }

  • Complex dewetting scenarios of ultrathin silicon films for large-scale nanoarchitectures
    • M. Naffouti, R. Backofen, M. Salvalaglio, T. Bottein, M. Lodari, A. Voigt, T. David, A. Benkouider, I. Fraj, L. Favre, A. Ronda, I. Berbezier, D. Grosso, M. Abbarchi, M. Bollani
    • Science Advances 3, eaao1472 (2017)
    • DOI   Abstract  

      Dewetting is a ubiquitous phenomenon in nature; many different thin films of organic and inorganic substances (such as liquids, polymers, metals, and semiconductors) share this shape instability driven by surface tension and mass transport. Via templated solid-state dewetting, we frame complex nanoarchitectures of monocrystalline silicon on insulator with unprecedented precision and reproducibility over large scales. Phase-field simulations reveal the dominant role of surface diffusion as a driving force for dewetting and provide a predictive tool to further engineer this hybrid top-down/bottom-up self-assembly method. Our results demonstrate that patches of thin monocrystalline films of metals and semiconductors share the same dewetting dynamics. We also prove the potential of our method by fabricating nanotransfer molding of metal oxide xerogels on silicon and glass substrates. This method allows the novel possibility of transferring these Si-based patterns on different materials, which do not usually undergo dewetting, offering great potential also for microfluidic or sensing applications. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science.

      @ARTICLE{Naffouti2017,
      author={Naffouti, M. and Backofen, R. and Salvalaglio, M. and Bottein, T. and Lodari, M. and Voigt, A. and David, T. and Benkouider, A. and Fraj, I. and Favre, L. and Ronda, A. and Berbezier, I. and Grosso, D. and Abbarchi, M. and Bollani, M.},
      title={Complex dewetting scenarios of ultrathin silicon films for large-scale nanoarchitectures},
      journal={Science Advances},
      year={2017},
      volume={3},
      number={11},
      doi={10.1126/sciadv.aao1472},
      art_number={eaao1472},
      note={cited By 44},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040445116&doi=10.1126%2fsciadv.aao1472&partnerID=40&md5=233409c2f1561f35327bce8efb4e860c},
      affiliation={Aix-Marseille Université, CNRS, Université de Toulon, IM2NP UMR 7334, Marseille, 13397, France; Laboratoire de Micro-Optoélectronique et Nanostructures, Faculté des Sciences de Monastir Université de Monastir, Monastir, 5019, Tunisia; Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Istituto di Fotonica, Nanotecnologie–Consiglio Nazionale delle Ricerche, Laboratory for Nanostructure Epitaxy and Spintronics on Silicon, Via Anzani 42, Como, 22100, Italy; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={Dewetting is a ubiquitous phenomenon in nature; many different thin films of organic and inorganic substances (such as liquids, polymers, metals, and semiconductors) share this shape instability driven by surface tension and mass transport. Via templated solid-state dewetting, we frame complex nanoarchitectures of monocrystalline silicon on insulator with unprecedented precision and reproducibility over large scales. Phase-field simulations reveal the dominant role of surface diffusion as a driving force for dewetting and provide a predictive tool to further engineer this hybrid top-down/bottom-up self-assembly method. Our results demonstrate that patches of thin monocrystalline films of metals and semiconductors share the same dewetting dynamics. We also prove the potential of our method by fabricating nanotransfer molding of metal oxide xerogels on silicon and glass substrates. This method allows the novel possibility of transferring these Si-based patterns on different materials, which do not usually undergo dewetting, offering great potential also for microfluidic or sensing applications. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science.},
      document_type={Article},
      source={Scopus},
      }

  • In-situ stretching patterned graphene nanoribbons in the transmission electron microscope
    • Z. Liao, L. M. Sandonas, T. Zhang, M. Gall, A. Dianat, R. Gutierrez, U. Mühle, J. Gluch, R. Jordan, G. Cuniberti, E. Zschech
    • Scientific Reports 7, 211 (2017)
    • DOI   Abstract  

      The mechanical response of patterned graphene nanoribbons (GNRs) with a width less than 100 nm was studied in-situ using quantitative tensile testing in a transmission electron microscope (TEM). A high degree of crystallinity was confirmed for patterned nanoribbons before and after the in-situ experiment by selected area electron diffraction (SAED) patterns. However, the maximum local true strain of the nanoribbons was determined to be only about 3%. The simultaneously recorded low-loss electron energy loss spectrum (EELS) on the stretched nanoribbons did not reveal any bandgap opening. Density Functional Based Tight Binding (DFTB) simulation was conducted to predict a feasible bandgap opening as a function of width in GNRs at low strain. The bandgap of unstrained armchair graphene nanoribbons (AGNRs) vanished for a width of about 14.75 nm, and this critical width was reduced to 11.21 nm for a strain level of 2.2%. The measured low tensile failure strain may limit the practical capability of tuning the bandgap of patterned graphene nanostructures by strain engineering, and therefore, it should be considered in bandgap design for graphene-based electronic devices by strain engineering. © The Author(s) 2017.

      @ARTICLE{Liao2017,
      author={Liao, Z. and Sandonas, L.M. and Zhang, T. and Gall, M. and Dianat, A. and Gutierrez, R. and Mühle, U. and Gluch, J. and Jordan, R. and Cuniberti, G. and Zschech, E.},
      title={In-situ stretching patterned graphene nanoribbons in the transmission electron microscope},
      journal={Scientific Reports},
      year={2017},
      volume={7},
      number={1},
      doi={10.1038/s41598-017-00227-3},
      art_number={211},
      note={cited By 13},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85038915081&doi=10.1038%2fs41598-017-00227-3&partnerID=40&md5=4a5e0f8b282ca08173c97042fdfc618b},
      affiliation={Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), Dresden, 01109, Germany; Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, 01069, Germany; Center for Advancing Electronics Dresden (Cfaed), Technische Universität Dresden, Dresden, 01062, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany; Department Chemie, Technische Universität Dresden, Dresden, 01069, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany},
      abstract={The mechanical response of patterned graphene nanoribbons (GNRs) with a width less than 100 nm was studied in-situ using quantitative tensile testing in a transmission electron microscope (TEM). A high degree of crystallinity was confirmed for patterned nanoribbons before and after the in-situ experiment by selected area electron diffraction (SAED) patterns. However, the maximum local true strain of the nanoribbons was determined to be only about 3%. The simultaneously recorded low-loss electron energy loss spectrum (EELS) on the stretched nanoribbons did not reveal any bandgap opening. Density Functional Based Tight Binding (DFTB) simulation was conducted to predict a feasible bandgap opening as a function of width in GNRs at low strain. The bandgap of unstrained armchair graphene nanoribbons (AGNRs) vanished for a width of about 14.75 nm, and this critical width was reduced to 11.21 nm for a strain level of 2.2%. The measured low tensile failure strain may limit the practical capability of tuning the bandgap of patterned graphene nanostructures by strain engineering, and therefore, it should be considered in bandgap design for graphene-based electronic devices by strain engineering. © The Author(s) 2017.},
      document_type={Article},
      source={Scopus},
      }

2016

  • B a2NiOs O6: A Dirac-Mott insulator with ferromagnetism near 100 K
    • H. L. Feng, S. Calder, M. P. Ghimire, Y. -H. Yuan, Y. Shirako, Y. Tsujimoto, Y. Matsushita, Z. Hu, C. -Y. Kuo, L. H. Tjeng, T. -W. Pi, Y. -L. Soo, J. He, M. Tanaka, Y. Katsuya, M. Richter, K. Yamaura
    • Physical Review B , 235158 (2016)
    • DOI   Abstract  

      The ferromagnetic semiconductor Ba2NiOsO6 (Tmag∼100K) was synthesized at 6 GPa and 1500 °C. It crystallizes into a double perovskite structure [Fm-3m; a=8.0428(1)Å], where the Ni2+ and Os6+ ions are perfectly ordered at the perovskite B site. We show that the spin-orbit coupling of Os6+ plays an essential role in opening the charge gap. The magnetic state was investigated by density functional theory calculations and powder neutron diffraction. The latter revealed a collinear ferromagnetic order in a >21kOe magnetic field at 5 K. The ferromagnetic gapped state is fundamentally different from that of known dilute magnetic semiconductors such as (Ga,Mn)As and (Cd,Mn)Te (Tmag<180K), the spin-gapless semiconductor Mn2CoAl (Tmag∼720K), and the ferromagnetic insulators EuO (Tmag∼70K) and Bi3Cr3O11 (Tmag∼220K). It is also qualitatively different from known ferrimagnetic insulators and semiconductors, which are characterized by an antiparallel spin arrangement. Our finding of the ferromagnetic semiconductivity of Ba2NiOsO6 should increase interest in the platinum group oxides, because this alternative class of materials should be useful in the development of spintronic, quantum magnetic, and related devices. © 2016 American Physical Society.

      @ARTICLE{Feng2016,
      author={Feng, H.L. and Calder, S. and Ghimire, M.P. and Yuan, Y.-H. and Shirako, Y. and Tsujimoto, Y. and Matsushita, Y. and Hu, Z. and Kuo, C.-Y. and Tjeng, L.H. and Pi, T.-W. and Soo, Y.-L. and He, J. and Tanaka, M. and Katsuya, Y. and Richter, M. and Yamaura, K.},
      title={B a2NiOs O6: A Dirac-Mott insulator with ferromagnetism near 100 K},
      journal={Physical Review B},
      year={2016},
      number={23},
      doi={10.1103/PhysRevB.94.235158},
      art_number={235158},
      note={cited By 34},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007552105&doi=10.1103%2fPhysRevB.94.235158&partnerID=40&md5=ba55a32873e8a3a15aa3a18c6389e9b4},
      affiliation={Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan; Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, Dresden, 01187, Germany; Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Leibniz Institute for Solid State and Materials Research, IFW Dresden, P.O. Box 270116, Dresden, D-01171, Germany; Condensed Matter Physics Research Center, Butwal-13, Rupandehi, Lumbini, Nepal; Graduate School of Chemical Sciences and Engineering, Hokkaido University, North 10 West 8, Kita-ku, Sapporo, Hokkaido, 060-0810, Japan; Department of Chemistry, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan; Materials Analysis Station, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan; National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan; Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan; Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, Kouto 1-1-1, Sayo-cho, Hyogo, 679-5148, Japan; Dresden Center for Computational Materials Science, DCMS, TU Dresden, Dresden, D-01069, Germany; Department of Crystalline Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603, Japan},
      abstract={The ferromagnetic semiconductor Ba2NiOsO6 (Tmag∼100K) was synthesized at 6 GPa and 1500 °C. It crystallizes into a double perovskite structure [Fm-3m; a=8.0428(1)Å], where the Ni2+ and Os6+ ions are perfectly ordered at the perovskite B site. We show that the spin-orbit coupling of Os6+ plays an essential role in opening the charge gap. The magnetic state was investigated by density functional theory calculations and powder neutron diffraction. The latter revealed a collinear ferromagnetic order in a >21kOe magnetic field at 5 K. The ferromagnetic gapped state is fundamentally different from that of known dilute magnetic semiconductors such as (Ga,Mn)As and (Cd,Mn)Te (Tmag<180K), the spin-gapless semiconductor Mn2CoAl (Tmag∼720K), and the ferromagnetic insulators EuO (Tmag∼70K) and Bi3Cr3O11 (Tmag∼220K). It is also qualitatively different from known ferrimagnetic insulators and semiconductors, which are characterized by an antiparallel spin arrangement. Our finding of the ferromagnetic semiconductivity of Ba2NiOsO6 should increase interest in the platinum group oxides, because this alternative class of materials should be useful in the development of spintronic, quantum magnetic, and related devices. © 2016 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Thin-film growth dynamics with shadowing effects by a phase-field approach
    • M. Salvalaglio, R. Backofen, A. Voigt
    • Physical Review B , 235432 (2016)
    • DOI   Abstract  

      Shadowing effects during the growth of nano- and microstructures are crucial for the realization of several technological applications. They are given by the shielding of the incoming material flux provided by the growing structures themselves. Their features have been deeply investigated by theoretical approaches, revealing important information to support experimental activities. However, comprehensive investigations able to follow every stage of the growth processes as a whole, particularly useful to design and understand targeted experiments, are still challenging. In this work, we study the thin-film growth dynamics by means of a diffuse interface approach accounting for both deposition with shadowing effects and surface diffusion driven by the minimization of the surface energy. In particular, we introduce the coupling between a phase-field model and the detailed calculation of the incoming material flux at the surface deposited from vacuum or vapor phase in the ballistic regime. This allows us to finely reproduce the realistic morphological evolution during the growth on nonflat substrates, also accounting for different flux distributions. A general assessment of the method, focusing on two-dimensional profiles, is provided thanks to the comparison with a sharp-interface approach for the evolution of the early stages. Then, the long-time-scale dynamics is shown in two and three dimensions, providing a general overview of the features observed during deposition on corrugated surfaces involving flattening, increasing of surface roughness with the growth of columnar structures, and voids formation. © 2016 American Physical Society.

      @ARTICLE{Salvalaglio2016,
      author={Salvalaglio, M. and Backofen, R. and Voigt, A.},
      title={Thin-film growth dynamics with shadowing effects by a phase-field approach},
      journal={Physical Review B},
      year={2016},
      number={23},
      doi={10.1103/PhysRevB.94.235432},
      art_number={235432},
      note={cited By 10},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007574676&doi=10.1103%2fPhysRevB.94.235432&partnerID=40&md5=cf41dc595a0bad9a0e518d77c0dd8cde},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; IHP, Im Technologiepark 25, Frankfurt (Oder), 15236, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={Shadowing effects during the growth of nano- and microstructures are crucial for the realization of several technological applications. They are given by the shielding of the incoming material flux provided by the growing structures themselves. Their features have been deeply investigated by theoretical approaches, revealing important information to support experimental activities. However, comprehensive investigations able to follow every stage of the growth processes as a whole, particularly useful to design and understand targeted experiments, are still challenging. In this work, we study the thin-film growth dynamics by means of a diffuse interface approach accounting for both deposition with shadowing effects and surface diffusion driven by the minimization of the surface energy. In particular, we introduce the coupling between a phase-field model and the detailed calculation of the incoming material flux at the surface deposited from vacuum or vapor phase in the ballistic regime. This allows us to finely reproduce the realistic morphological evolution during the growth on nonflat substrates, also accounting for different flux distributions. A general assessment of the method, focusing on two-dimensional profiles, is provided thanks to the comparison with a sharp-interface approach for the evolution of the early stages. Then, the long-time-scale dynamics is shown in two and three dimensions, providing a general overview of the features observed during deposition on corrugated surfaces involving flattening, increasing of surface roughness with the growth of columnar structures, and voids formation. © 2016 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Microscale modeling and simulation of magnetorheological elastomers at finite strains: A study on the influence of mechanical preloads
    • K. A. Kalina, P. Metsch, M. Kästner
    • International Journal of Solids and Structures 102-103, 286-296 (2016)
    • DOI   Abstract  

      Herein, we present a numerical study on the deformation dependent behavior of magnetorheological elastomers with structured and unstructured particle distributions. To this end, finite element simulations are performed in order to calculate the effective magnetization and macroscopic actuation stresses for different specimens with realistic microstructures and varying mechanical preloads. Since the proposed microscale model is based on a continuum formulation of the magnetomechanical boundary value problem, the local magnetic and mechanical fields are resolved explicitly within the microstructures. The consideration of finite strains results in a finite element implementation of the coupled field problem for which a consistent linearization scheme is presented. In order to provide a better understanding of the deformation dependent behavior in real specimens, a study on chain-like structures is performed. It reveals that the interaction of the constituents in chain-like structures yields different material responses depending on their position. These findings are used to explain the influence of mechanical preloads on the behavior of samples with structured and unstructured arrangements of the particles. All of our results are in good agreement with experimental investigations which have been carried out for magnetorheological elastomers comprising a structured particle distribution. © 2016 Elsevier Ltd

      @ARTICLE{Kalina2016286,
      author={Kalina, K.A. and Metsch, P. and Kästner, M.},
      title={Microscale modeling and simulation of magnetorheological elastomers at finite strains: A study on the influence of mechanical preloads},
      journal={International Journal of Solids and Structures},
      year={2016},
      volume={102-103},
      pages={286-296},
      doi={10.1016/j.ijsolstr.2016.10.019},
      note={cited By 32},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995581786&doi=10.1016%2fj.ijsolstr.2016.10.019&partnerID=40&md5=23e1e1e487e53f36d1dec30db8c86819},
      affiliation={Institute of Solid Mechanics, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={Herein, we present a numerical study on the deformation dependent behavior of magnetorheological elastomers with structured and unstructured particle distributions. To this end, finite element simulations are performed in order to calculate the effective magnetization and macroscopic actuation stresses for different specimens with realistic microstructures and varying mechanical preloads. Since the proposed microscale model is based on a continuum formulation of the magnetomechanical boundary value problem, the local magnetic and mechanical fields are resolved explicitly within the microstructures. The consideration of finite strains results in a finite element implementation of the coupled field problem for which a consistent linearization scheme is presented. In order to provide a better understanding of the deformation dependent behavior in real specimens, a study on chain-like structures is performed. It reveals that the interaction of the constituents in chain-like structures yields different material responses depending on their position. These findings are used to explain the influence of mechanical preloads on the behavior of samples with structured and unstructured arrangements of the particles. All of our results are in good agreement with experimental investigations which have been carried out for magnetorheological elastomers comprising a structured particle distribution. © 2016 Elsevier Ltd},
      author_keywords={Finite element method; Finite strains; Magnetoelasticity; Magnetomechanical coupling},
      document_type={Article},
      source={Scopus},
      }

  • Experimental characterisation and numerical modelling of cutting processes in viscoelastic solids
    • M. Boisly, S. Schuldt, M. Kästner, Y. Schneider, H. Rohm
    • Journal of Food Engineering 191, 1-9 (2016)
    • DOI   Abstract  

      Rate dependency is an important phenomenon that can be observed during cutting of viscoelastic materials. This paper reports on results of both experimental and theoretical investigations that were obtained by using a polymeric food model system. Viscoelasticity was experimentally observed in relaxation experiments at small strains, and tensile tests were performed for large deformations at different tensile speeds. Finite viscoelasticity with MOONEY-RIVLIN elasticity valid for large displacements was applied for modelling the viscoelastic properties of the food model, and degradation and crack propagation were considered by cohesive fracture mechanisms. Model predictions were prepared by applying the finite element method using Abaqus and compared with experimental results. The good agreement between simulation and measurement especially for the maximum cutting force and the characteristic plateau validate the modelling strategy. © 2016 Elsevier Ltd

      @ARTICLE{Boisly20161,
      author={Boisly, M. and Schuldt, S. and Kästner, M. and Schneider, Y. and Rohm, H.},
      title={Experimental characterisation and numerical modelling of cutting processes in viscoelastic solids},
      journal={Journal of Food Engineering},
      year={2016},
      volume={191},
      pages={1-9},
      doi={10.1016/j.jfoodeng.2016.06.019},
      note={cited By 13},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978194792&doi=10.1016%2fj.jfoodeng.2016.06.019&partnerID=40&md5=6a82d221cb72b93962306c15288794dc},
      affiliation={Institute of Solid Mechanics, TU Dresden, Dresden, 01062, Germany; Institute of Food Technology and Bioprocess Engineering, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany},
      abstract={Rate dependency is an important phenomenon that can be observed during cutting of viscoelastic materials. This paper reports on results of both experimental and theoretical investigations that were obtained by using a polymeric food model system. Viscoelasticity was experimentally observed in relaxation experiments at small strains, and tensile tests were performed for large deformations at different tensile speeds. Finite viscoelasticity with MOONEY-RIVLIN elasticity valid for large displacements was applied for modelling the viscoelastic properties of the food model, and degradation and crack propagation were considered by cohesive fracture mechanisms. Model predictions were prepared by applying the finite element method using Abaqus and compared with experimental results. The good agreement between simulation and measurement especially for the maximum cutting force and the characteristic plateau validate the modelling strategy. © 2016 Elsevier Ltd},
      author_keywords={Cohesive fracture; Cutting; Finite element modelling; Foods; Model system; Relaxation},
      document_type={Article},
      source={Scopus},
      }

  • Electronically driven single-molecule switch on silicon dangling bonds
    • A. Nickel, T. Lehmann, J. Meyer, F. Eisenhut, R. Ohmann, D. A. Ryndyk, C. Joachim, F. Moresco, G. Cuniberti
    • Journal of Physical Chemistry C 120, 27027-27032 (2016)
    • DOI   Abstract  

      We demonstrate that a single 4-acetylbiphenyl molecule adsorbed along the dimer row of a Si(100)-(2 × 1) surface can be reversibly switched between two stable conformations using the tunneling current of a scanning tunneling microscope. The experiment supported by density functional theory calculations demonstrates that the molecule by switching selectively passivates and depassivates a dangling-bond pair on the silicon surface, opening new routes for the logical input in dangling-bond-based atomic-scale circuits. © 2016 American Chemical Society.

      @ARTICLE{Nickel201627027,
      author={Nickel, A. and Lehmann, T. and Meyer, J. and Eisenhut, F. and Ohmann, R. and Ryndyk, D.A. and Joachim, C. and Moresco, F. and Cuniberti, G.},
      title={Electronically driven single-molecule switch on silicon dangling bonds},
      journal={Journal of Physical Chemistry C},
      year={2016},
      volume={120},
      number={47},
      pages={27027-27032},
      doi={10.1021/acs.jpcc.6b05680},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-85041904829&doi=10.1021%2facs.jpcc.6b05680&partnerID=40&md5=c288d81efeae5f1fe0975e7fe5ecea06},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; GNS and MANA Satellite, CEMES, CNRS, 29 Rue J. Marvig, Toulouse Cedex, 31055, France; International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Energy Materials and Surface Sciences Unit (EMSS), Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan},
      abstract={We demonstrate that a single 4-acetylbiphenyl molecule adsorbed along the dimer row of a Si(100)-(2 × 1) surface can be reversibly switched between two stable conformations using the tunneling current of a scanning tunneling microscope. The experiment supported by density functional theory calculations demonstrates that the molecule by switching selectively passivates and depassivates a dangling-bond pair on the silicon surface, opening new routes for the logical input in dangling-bond-based atomic-scale circuits. © 2016 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Probing Silica-Biomolecule Interactions by Solid-State NMR and Molecular Dynamics Simulations
    • S. I. Brückner, S. Donets, A. Dianat, M. Bobeth, R. Gutiérrez, G. Cuniberti, E. Brunner
    • Langmuir 32, 11698-11705 (2016)
    • DOI   Abstract  

      Understanding the molecular interactions between inorganic phases such as silica and organic material is fundamental for chromatographic applications, for tailoring silica-enzyme interactions, and for elucidating the mechanisms of biomineralization. The formation, structure, and properties of the organic/inorganic interface is crucial in this context. Here, we investigate the interaction of selectively 13C-labeled choline with 29Si-labeled monosilicic acid/silica at the molecular level. Silica/choline nanocomposites were analyzed by solid-state NMR spectroscopy in combination with extended molecular dynamics (MD) simulations to understand the silica/organic interface. Cross-polarization magic angle spinning (CP MAS)-based NMR experiments like 1H-13C CP-REDOR (rotational-echo double resonance), 1H-13C HETCOR (heteronuclear correlation), and 1H-29Si-1H double CP are employed to determine spatial parameters. The measurement of 29Si-13C internuclear distances for selectively 13C-labeled choline provides an experimental parameter that allows the direct verification of MD simulations. Atomistic modeling using classical MD methodologies is performed using the INTERFACE force field. The modeling results are in excellent agreement with the experimental data and reveal the relevant molecular conformations as well as the nature and interplay of the interactions between the choline cation and the silica surface. Electrostatic interactions and hydrogen bonding are both important and depend strongly on the hydration level as well as the charge state of the silica surface. © 2016 American Chemical Society.

      @ARTICLE{Brückner201611698,
      author={Brückner, S.I. and Donets, S. and Dianat, A. and Bobeth, M. and Gutiérrez, R. and Cuniberti, G. and Brunner, E.},
      title={Probing Silica-Biomolecule Interactions by Solid-State NMR and Molecular Dynamics Simulations},
      journal={Langmuir},
      year={2016},
      volume={32},
      number={44},
      pages={11698-11705},
      doi={10.1021/acs.langmuir.6b03311},
      note={cited By 9},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994731843&doi=10.1021%2facs.langmuir.6b03311&partnerID=40&md5=e961b95e1c793da234caddcb77a3652a},
      affiliation={Department of Bioanalytical Chemistry, Department of Chemistry and Food Chemistry, TU Dresden, Dresden, 01062, Germany; Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Understanding the molecular interactions between inorganic phases such as silica and organic material is fundamental for chromatographic applications, for tailoring silica-enzyme interactions, and for elucidating the mechanisms of biomineralization. The formation, structure, and properties of the organic/inorganic interface is crucial in this context. Here, we investigate the interaction of selectively 13C-labeled choline with 29Si-labeled monosilicic acid/silica at the molecular level. Silica/choline nanocomposites were analyzed by solid-state NMR spectroscopy in combination with extended molecular dynamics (MD) simulations to understand the silica/organic interface. Cross-polarization magic angle spinning (CP MAS)-based NMR experiments like 1H-13C CP-REDOR (rotational-echo double resonance), 1H-13C HETCOR (heteronuclear correlation), and 1H-29Si-1H double CP are employed to determine spatial parameters. The measurement of 29Si-13C internuclear distances for selectively 13C-labeled choline provides an experimental parameter that allows the direct verification of MD simulations. Atomistic modeling using classical MD methodologies is performed using the INTERFACE force field. The modeling results are in excellent agreement with the experimental data and reveal the relevant molecular conformations as well as the nature and interplay of the interactions between the choline cation and the silica surface. Electrostatic interactions and hydrogen bonding are both important and depend strongly on the hydration level as well as the charge state of the silica surface. © 2016 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • A numerical study on magnetostrictive phenomena in magnetorheological elastomers
    • P. Metsch, K. A. Kalina, C. Spieler, M. Kästner
    • Computational Materials Science 124, 364-374 (2016)
    • DOI   Abstract  

      Herein, we present an investigation on magnetostrictive phenomena in magnetorheological elastomers. By using a continuum approach, constitutive as well as geometric properties on the microscale are taken into account in order to predict the effective behavior of these composites by means of a computational homogenization. Thus, the magnetic and mechanical fields are resolved explicitly without the simplifying assumption of dipoles. In the present work, a modeling strategy which accounts for elastic constituents and a nonlinear magnetization behavior of the particles is pursued. In order to provide a better understanding of fundamental deformation mechanisms, idealized lattices as well as compact and wavy chains are considered within a first study. Our results confirm assumptions stated in the literature according to which macroscopic magnetostriction can be ascribed to microscopic particle movements that result in an improved microstructure. The simulations that are performed for the subsequent investigations on random microstructures with different particle-volume fractions are evaluated statistically to ensure validity of our findings. They reveal anisotropic as well as isotropic macroscopic behavior for structured and unstructured particle distributions, respectively. In view of the macroscopic magnetostriction, all the results presented in this contribution are in good agreement with current experimental and theoretical findings. © 2016 Elsevier B.V.

      @ARTICLE{Metsch2016364,
      author={Metsch, P. and Kalina, K.A. and Spieler, C. and Kästner, M.},
      title={A numerical study on magnetostrictive phenomena in magnetorheological elastomers},
      journal={Computational Materials Science},
      year={2016},
      volume={124},
      pages={364-374},
      doi={10.1016/j.commatsci.2016.08.012},
      note={cited By 67},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983371929&doi=10.1016%2fj.commatsci.2016.08.012&partnerID=40&md5=9c0a2340fa3043f99f76b69944e44ebf},
      affiliation={Institute of Solid Mechanics, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={Herein, we present an investigation on magnetostrictive phenomena in magnetorheological elastomers. By using a continuum approach, constitutive as well as geometric properties on the microscale are taken into account in order to predict the effective behavior of these composites by means of a computational homogenization. Thus, the magnetic and mechanical fields are resolved explicitly without the simplifying assumption of dipoles. In the present work, a modeling strategy which accounts for elastic constituents and a nonlinear magnetization behavior of the particles is pursued. In order to provide a better understanding of fundamental deformation mechanisms, idealized lattices as well as compact and wavy chains are considered within a first study. Our results confirm assumptions stated in the literature according to which macroscopic magnetostriction can be ascribed to microscopic particle movements that result in an improved microstructure. The simulations that are performed for the subsequent investigations on random microstructures with different particle-volume fractions are evaluated statistically to ensure validity of our findings. They reveal anisotropic as well as isotropic macroscopic behavior for structured and unstructured particle distributions, respectively. In view of the macroscopic magnetostriction, all the results presented in this contribution are in good agreement with current experimental and theoretical findings. © 2016 Elsevier B.V.},
      author_keywords={Magnetoelasticity; Magnetorheological elastomers; Magnetostriction},
      document_type={Article},
      source={Scopus},
      }

  • An algorithmic scheme for the automated calculation of fiber orientations in arterial walls
    • S. Fausten, D. Balzani, J. Schröder
    • Computational Mechanics 58, 861-878 (2016)
    • DOI   Abstract  

      We propose an algorithmic scheme for the numerical calculation of fiber orientations in arterial walls. The basic assumption behind the procedure is that the fiber orientations are mainly governed by the principal tensile stress directions resulting in an improved load transfer within the artery as a consequence of the redistribution of stresses. This reflects the biological motivation that soft tissues continuously adapt to their mechanical environment in order to optimize their load-bearing capacities. The algorithmic scheme proposed here enhances efficiency of the general procedure given in Hariton et al. (Biomech Model Mechanobiol 6(3):163–175, 2007), which consists of repeatedly identifying a favored fiber orientation based on the principal tensile stresses under a certain loading scenario, and then re-calculating the stresses for that loading scenario with the modified favored fiber orientation. Since the method still depends on a highly accurate stress approximation of the finite element formulation, which is not straightforward to obtain in particular for incompressible and highly anisotropic materials, furthermore, a modified model is introduced. This model defines the favored fiber orientation not only in terms of the local principal stresses, but in terms of the volume averages of the principal stresses computed over individual finite elements. Thereby, the influence of imperfect stress approximations can be weakened leading to a stabilized convergence of the reorientation procedure and a more reasonable fiber orientation with less numerical noise. The performance of the proposed fiber reorientation scheme is investigated with respect to different finite element formulations and different favored fiber orientation models, Hariton et al. (Biomech Model Mechanobiol 6(3):163–175, 2007) and Cyron and Humphrey (Math Mech Solids 1–17, 2014). In addition, it is applied to calculate the fiber orientation in a patient-specific arterial geometry. © 2016, Springer-Verlag Berlin Heidelberg.

      @ARTICLE{Fausten2016861,
      author={Fausten, S. and Balzani, D. and Schröder, J.},
      title={An algorithmic scheme for the automated calculation of fiber orientations in arterial walls},
      journal={Computational Mechanics},
      year={2016},
      volume={58},
      number={5},
      pages={861-878},
      doi={10.1007/s00466-016-1321-z},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982267397&doi=10.1007%2fs00466-016-1321-z&partnerID=40&md5=3d48be20bbe59f0b9a45c46ebe5b826f},
      affiliation={Institut für Mechanik, Fachbereich für Ingenieurwissenschaften/Abtl. Bauwissenschaften, Universität Duisburg-Essen, Universitätsstr. 15, Essen, 45141, Germany; Institut für Mechanik und Flächentragwerke/Fakultät Bauingenieurwesen, TU Dresden, August-Bebel-Str. 30, Dresden, 01219, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany},
      abstract={We propose an algorithmic scheme for the numerical calculation of fiber orientations in arterial walls. The basic assumption behind the procedure is that the fiber orientations are mainly governed by the principal tensile stress directions resulting in an improved load transfer within the artery as a consequence of the redistribution of stresses. This reflects the biological motivation that soft tissues continuously adapt to their mechanical environment in order to optimize their load-bearing capacities. The algorithmic scheme proposed here enhances efficiency of the general procedure given in Hariton et al. (Biomech Model Mechanobiol 6(3):163–175, 2007), which consists of repeatedly identifying a favored fiber orientation based on the principal tensile stresses under a certain loading scenario, and then re-calculating the stresses for that loading scenario with the modified favored fiber orientation. Since the method still depends on a highly accurate stress approximation of the finite element formulation, which is not straightforward to obtain in particular for incompressible and highly anisotropic materials, furthermore, a modified model is introduced. This model defines the favored fiber orientation not only in terms of the local principal stresses, but in terms of the volume averages of the principal stresses computed over individual finite elements. Thereby, the influence of imperfect stress approximations can be weakened leading to a stabilized convergence of the reorientation procedure and a more reasonable fiber orientation with less numerical noise. The performance of the proposed fiber reorientation scheme is investigated with respect to different finite element formulations and different favored fiber orientation models, Hariton et al. (Biomech Model Mechanobiol 6(3):163–175, 2007) and Cyron and Humphrey (Math Mech Solids 1–17, 2014). In addition, it is applied to calculate the fiber orientation in a patient-specific arterial geometry. © 2016, Springer-Verlag Berlin Heidelberg.},
      author_keywords={Arterial walls; Collagen fibers; Fiber reorientation; Finite element method},
      document_type={Article},
      source={Scopus},
      }

  • Reusability of photocatalytic TiO 2 and ZnO nanoparticles immobilized in poly(vinylidene difluoride)-co-trifluoroethylene
    • S. Teixeira, P. M. Martins, S. Lanceros-Méndez, K. Kühn, G. Cuniberti
    • Applied Surface Science 384, 497-504 (2016)
    • DOI   Abstract  

      Pollutants present in water are increasingly becoming an important public health issue. After their transportation across the sewer network they can pass through the wastewater treatment plants (WWTPs) mostly unchanged because WWTPs are not designed to remove pollutants present at trace levels. Conventional treatments are therefore ineffective. Immobilized photocatalytic systems are thus an advantage for the treatment of contaminated water, because they are ecofriendly, cost-effective and allow reusability. This work reports on TiO 2 and ZnO commercial nanoparticles immobilized in poly(vinylidene difluoride)-co-trifluoroethylene (P(VDF-TrFE)). Nanocomposites of P(VDF-TrFE) with different concentrations of TiO 2 nanoparticles (5, 10, and 15 wt.%) and ZnO nanoparticles (15 wt.%) were produced by solvent casting and tested on the degradation of methylene blue, a model organic dye. Each nanocomposite was tested three times to assess its reusability. It is shown that increasing the photocatalyst concentration results in higher photocatalytic efficiencies; the degradation rates of 15% of TiO 2 and ZnO are similar; and the photoactivity decreases 6%, 16%, 13%, and 11% after three utilizations, for TiO 2 5%, TiO 2 10%, TiO 2 15%, and ZnO 15%, respectively. Thus, the low decrease in the photocatalytic activity after three uses makes the nanocomposites suitable for applications in which reusability is an important key factor. © 2016 Elsevier B.V.

      @ARTICLE{Teixeira2016497,
      author={Teixeira, S. and Martins, P.M. and Lanceros-Méndez, S. and Kühn, K. and Cuniberti, G.},
      title={Reusability of photocatalytic TiO 2 and ZnO nanoparticles immobilized in poly(vinylidene difluoride)-co-trifluoroethylene},
      journal={Applied Surface Science},
      year={2016},
      volume={384},
      pages={497-504},
      doi={10.1016/j.apsusc.2016.05.073},
      note={cited By 61},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971268393&doi=10.1016%2fj.apsusc.2016.05.073&partnerID=40&md5=fe097043cfa85438b779ec8c1dc8bb9d},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Centro/Departamento de Física, Universidade Do Minho, Campus de Gualtar, Braga, 4710-057, Portugal; Centro de Engenharia Biológica, Universidade Do Minho, Braga, 4710-057, Portugal; BCMaterials, Parque Científico y Tecnológico de Bizkaia, Derio, 48160, Spain; IKERBASQUE, Basque Foundation for Science, Bilbao, Spain; Dresden Center for Computational Materials Science (DCCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Pollutants present in water are increasingly becoming an important public health issue. After their transportation across the sewer network they can pass through the wastewater treatment plants (WWTPs) mostly unchanged because WWTPs are not designed to remove pollutants present at trace levels. Conventional treatments are therefore ineffective. Immobilized photocatalytic systems are thus an advantage for the treatment of contaminated water, because they are ecofriendly, cost-effective and allow reusability. This work reports on TiO 2 and ZnO commercial nanoparticles immobilized in poly(vinylidene difluoride)-co-trifluoroethylene (P(VDF-TrFE)). Nanocomposites of P(VDF-TrFE) with different concentrations of TiO 2 nanoparticles (5, 10, and 15 wt.%) and ZnO nanoparticles (15 wt.%) were produced by solvent casting and tested on the degradation of methylene blue, a model organic dye. Each nanocomposite was tested three times to assess its reusability. It is shown that increasing the photocatalyst concentration results in higher photocatalytic efficiencies; the degradation rates of 15% of TiO 2 and ZnO are similar; and the photoactivity decreases 6%, 16%, 13%, and 11% after three utilizations, for TiO 2 5%, TiO 2 10%, TiO 2 15%, and ZnO 15%, respectively. Thus, the low decrease in the photocatalytic activity after three uses makes the nanocomposites suitable for applications in which reusability is an important key factor. © 2016 Elsevier B.V.},
      author_keywords={Catalyst; Membrane; Methylene blue; Nanocomposites; Remediation},
      document_type={Article},
      source={Scopus},
      }

  • Computational study of structure, electronic, and microscopic charge transport properties of small conjugated diketopyrrolopyrrole-thiophene molecules
    • M. V. Makarova, S. G. Semenov, O. A. Guskova
    • International Journal of Quantum Chemistry 116, 1459-1466 (2016)
    • DOI   Abstract  

      π-Conjugated small molecules containing diketopyrrolopyrrole (DPP) and thiophene moieties represent a modern class of functional materials that exhibit promising charge transport properties and therefore have great potential as building blocks of active elements of electronic devices. As a starting point of this computational study, the molecular structure, electronic characteristics, and reorganization energies associated with electron or hole transfer are considered. Prediction of molecular crystal packing is followed by the calculation of couplings between adjacent molecules and detection of the effective charge transfer pathways. Finally, the rates of charge transfer process are evaluated. The obtained results shed light not only on the properties of materials containing low-molecular species but also serve as a benchmark for further classical force-field simulations of DPP-based polymers. © 2016 Wiley Periodicals, Inc.

      @ARTICLE{Makarova20161459,
      author={Makarova, M.V. and Semenov, S.G. and Guskova, O.A.},
      title={Computational study of structure, electronic, and microscopic charge transport properties of small conjugated diketopyrrolopyrrole-thiophene molecules},
      journal={International Journal of Quantum Chemistry},
      year={2016},
      volume={116},
      number={20},
      pages={1459-1466},
      doi={10.1002/qua.25205},
      note={cited By 9},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978196599&doi=10.1002%2fqua.25205&partnerID=40&md5=c0253f49fc225ee297c342ad84be9b4f},
      affiliation={Leibniz-Institut für Polymerforschung Dresden e.V, Institut Theorie der Polymere, Hohe Straße 6, Dresden, 01069, Germany; Petersburg Nuclear Physics Institute, National Research Centre “Kurchatov Institute,” Orlova Roscha, Gatchina, 188300, Russian Federation; Technische Universität Dresden, Dresden Center for Computational Materials Science (DCMS)01062, Germany},
      abstract={π-Conjugated small molecules containing diketopyrrolopyrrole (DPP) and thiophene moieties represent a modern class of functional materials that exhibit promising charge transport properties and therefore have great potential as building blocks of active elements of electronic devices. As a starting point of this computational study, the molecular structure, electronic characteristics, and reorganization energies associated with electron or hole transfer are considered. Prediction of molecular crystal packing is followed by the calculation of couplings between adjacent molecules and detection of the effective charge transfer pathways. Finally, the rates of charge transfer process are evaluated. The obtained results shed light not only on the properties of materials containing low-molecular species but also serve as a benchmark for further classical force-field simulations of DPP-based polymers. © 2016 Wiley Periodicals, Inc.},
      author_keywords={charge transfer parameters; density functional theory; diketopyrrolopyrrole; packing prediction},
      document_type={Article},
      source={Scopus},
      }

  • Borophene as an anode material for Ca, Mg, Na or Li ion storage: A first-principle study
    • B. Mortazavi, A. Dianat, O. Rahaman, G. Cuniberti, T. Rabczuk
    • Journal of Power Sources 329, 456-461 (2016)
    • DOI   Abstract  

      Borophene, the boron atom analogue to graphene, being atomic thick have been just recently experimentally fabricated. In this work, we employ first-principles density functional theory calculations to investigate the interaction of Ca, Mg, Na or Li atoms with single-layer and free-standing borophene. We first identified the most stable binding sites and their corresponding binding energies as well and then we gradually increased the ions concentration. Our calculations predict strong binding energies of around 4.03 eV, 2.09 eV, 2.92 eV and 3.28 eV between the borophene substrate and Ca, Mg, Na or Li ions, respectively. We found that the binding energy generally decreases by increasing the ions content. Using the Bader charge analysis, we evaluate the charge transfer between the adatoms and the borophene sheet. Our investigation proposes the borophene as a 2D material with a remarkably high capacity of around 800 mA h/g, 1960 mA h/g, 1380 mA h/g and 1720 mA h/g for Ca, Mg, Na or Li ions storage, respectively. This study can be useful for the possible application of borophene for the rechargeable ion batteries. © 2016 Elsevier B.V.

      @ARTICLE{Mortazavi2016456,
      author={Mortazavi, B. and Dianat, A. and Rahaman, O. and Cuniberti, G. and Rabczuk, T.},
      title={Borophene as an anode material for Ca, Mg, Na or Li ion storage: A first-principle study},
      journal={Journal of Power Sources},
      year={2016},
      volume={329},
      pages={456-461},
      doi={10.1016/j.jpowsour.2016.08.109},
      note={cited By 116},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984822399&doi=10.1016%2fj.jpowsour.2016.08.109&partnerID=40&md5=5e5747ff2864cae5579d3ece1b4edc3e},
      affiliation={Institute of Structural Mechanics, Bauhaus-Universität Weimar, Marienstr. 15, Weimar, D-99423, Germany; Institute for Materials Science and Max Bergman Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, D-01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Borophene, the boron atom analogue to graphene, being atomic thick have been just recently experimentally fabricated. In this work, we employ first-principles density functional theory calculations to investigate the interaction of Ca, Mg, Na or Li atoms with single-layer and free-standing borophene. We first identified the most stable binding sites and their corresponding binding energies as well and then we gradually increased the ions concentration. Our calculations predict strong binding energies of around 4.03 eV, 2.09 eV, 2.92 eV and 3.28 eV between the borophene substrate and Ca, Mg, Na or Li ions, respectively. We found that the binding energy generally decreases by increasing the ions content. Using the Bader charge analysis, we evaluate the charge transfer between the adatoms and the borophene sheet. Our investigation proposes the borophene as a 2D material with a remarkably high capacity of around 800 mA h/g, 1960 mA h/g, 1380 mA h/g and 1720 mA h/g for Ca, Mg, Na or Li ions storage, respectively. This study can be useful for the possible application of borophene for the rechargeable ion batteries. © 2016 Elsevier B.V.},
      author_keywords={2D material; Batteries; Borophene; First-principles; Li ions; Modelling},
      document_type={Article},
      source={Scopus},
      }

  • Collective migration under hydrodynamic interactions: A computational approach
    • W. Marth, A. Voigt
    • Interface Focus 6(2016)
    • DOI   Abstract  

      We consider a generic model for cell motility. Even if a comprehensive understanding of cell motility remains elusive, progress has been achieved in its modelling using a whole-cell physical model. The model takes into account the main mechanisms of cell motility, actin polymerization, actin–myosin dynamics and substrate mediated adhesion (if applicable), and combines them with steric cell–cell and hydrodynamic interactions. The model predicts the onset of collective cell migration, which emerges spontaneously as a result of inelastic collisions of neighbouring cells. Each cell here modelled as an active polar gel is accomplished with two vortices if it moves. Upon collision of two cells, the two vortices which come close to each other annihilate. This leads to a rotation of the cells and together with the deformation and the reorientation of the actin filaments in each cell induces alignment of these cells and leads to persistent translational collective migration. The effect for low Reynolds numbers is as strong as in the non-hydrodynamic model, but it decreases with increasing Reynolds number. © 2016 The Author(s) Published by the Royal Society. All rights reserved.

      @ARTICLE{Marth2016,
      author={Marth, W. and Voigt, A.},
      title={Collective migration under hydrodynamic interactions: A computational approach},
      journal={Interface Focus},
      year={2016},
      volume={6},
      number={5},
      page_count={8},
      doi={10.1098/rsfs.2016.0037},
      note={cited By 12},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983412973&doi=10.1098%2frsfs.2016.0037&partnerID=40&md5=74b41cd358e830457291b6553d25a691},
      affiliation={Institut für Wissenschaftliches Rechnen, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Systems Biology Dresden (CSBD), Pfotenhauerstr. 108, Dresden, 01307, Germany},
      abstract={We consider a generic model for cell motility. Even if a comprehensive understanding of cell motility remains elusive, progress has been achieved in its modelling using a whole-cell physical model. The model takes into account the main mechanisms of cell motility, actin polymerization, actin–myosin dynamics and substrate mediated adhesion (if applicable), and combines them with steric cell–cell and hydrodynamic interactions. The model predicts the onset of collective cell migration, which emerges spontaneously as a result of inelastic collisions of neighbouring cells. Each cell here modelled as an active polar gel is accomplished with two vortices if it moves. Upon collision of two cells, the two vortices which come close to each other annihilate. This leads to a rotation of the cells and together with the deformation and the reorientation of the actin filaments in each cell induces alignment of these cells and leads to persistent translational collective migration. The effect for low Reynolds numbers is as strong as in the non-hydrodynamic model, but it decreases with increasing Reynolds number. © 2016 The Author(s) Published by the Royal Society. All rights reserved.},
      author_keywords={Active polar gel theory; Collective cell migration; Hydrodynamic interactions},
      document_type={Article},
      source={Scopus},
      }

  • Incompressible two-phase flows with an inextensible Newtonian fluid interface
    • S. Reuther, A. Voigt
    • Journal of Computational Physics 322, 850-858 (2016)
    • DOI   Abstract  

      We introduce a diffuse interface approximation for an incompressible two-phase flow problem with an inextensible Newtonian fluid interface. This approach allows to model lipid membranes as viscous fluids. In the present setting the membranes are assumed to be stationary. We validate the model and the numerical approach, which is based on a stream function formulation for the surface flow problem, an operator splitting approach and a semi-implicit adaptive finite element discretization, against observed flow patterns in vesicles, which are adhered to a solid surface and are subjected to shear flow. The influence of the Gaussian curvature on the surface flow pattern is discussed. © 2016 Elsevier Inc.

      @ARTICLE{Reuther2016850,
      author={Reuther, S. and Voigt, A.},
      title={Incompressible two-phase flows with an inextensible Newtonian fluid interface},
      journal={Journal of Computational Physics},
      year={2016},
      volume={322},
      pages={850-858},
      doi={10.1016/j.jcp.2016.07.023},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979517407&doi=10.1016%2fj.jcp.2016.07.023&partnerID=40&md5=f86278dea378e7440067308a1cc6272a},
      affiliation={Institute of Scientific Computing, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Systems Biology Dresden (CSBD), Pfotenhauerstr 108, Dresden, 01307, Germany},
      abstract={We introduce a diffuse interface approximation for an incompressible two-phase flow problem with an inextensible Newtonian fluid interface. This approach allows to model lipid membranes as viscous fluids. In the present setting the membranes are assumed to be stationary. We validate the model and the numerical approach, which is based on a stream function formulation for the surface flow problem, an operator splitting approach and a semi-implicit adaptive finite element discretization, against observed flow patterns in vesicles, which are adhered to a solid surface and are subjected to shear flow. The influence of the Gaussian curvature on the surface flow pattern is discussed. © 2016 Elsevier Inc.},
      author_keywords={Diffuse interface approximation; Interfacial fluids; Lipid membranes},
      document_type={Article},
      source={Scopus},
      }

  • A novel mixed finite element for finite anisotropic elasticity; the SKA-element Simplified Kinematics for Anisotropy
    • J. Schröder, N. Viebahn, D. Balzani, P. Wriggers
    • Computer Methods in Applied Mechanics and Engineering 310, 475-494 (2016)
    • DOI   Abstract  

      A variety of numerical approximation schemes for boundary value problems suffer from so-called locking-phenomena. It is well known that in such cases several finite element formulations exhibit poor convergence rates in the basic variables. A serious locking phenomenon can be observed in the case of anisotropic elasticity, due to high stiffness in preferred directions. The main goal of this paper is to overcome this locking problem in anisotropic hyperelasticity by introducing a novel mixed variational framework. Therefore we split the strain energy into two main parts, an isotropic and an anisotropic part. For the isotropic part we can apply different well-established approximation schemes and for the anisotropic part we apply a constant approximation of the deformation gradient or the right Cauchy–Green tensor. This additional constraint is attached to the strain energy function by a second-order tensorial Lagrange-multiplier, governed by a Simplified Kinematic for the Anisotropic part. As a matter of fact, for the tested boundary value problems the SKA-element based on quadratic ansatz functions for the displacements, performs excellent and behaves more robust than competitive formulations. © 2016 Elsevier B.V.

      @ARTICLE{Schröder2016475,
      author={Schröder, J. and Viebahn, N. and Balzani, D. and Wriggers, P.},
      title={A novel mixed finite element for finite anisotropic elasticity; the SKA-element Simplified Kinematics for Anisotropy},
      journal={Computer Methods in Applied Mechanics and Engineering},
      year={2016},
      volume={310},
      pages={475-494},
      doi={10.1016/j.cma.2016.06.029},
      note={cited By 24},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84980494077&doi=10.1016%2fj.cma.2016.06.029&partnerID=40&md5=9549002413410b282d2ca7ddcc28786a},
      affiliation={Institut für Mechanik, Fachbereich für Ingenieurwissenschaften/Abtl. Bauwissenschaften, Universität Duisburg-Essen, 45117 Essen, Universitätsstr. 15, Germany; Institut für Mechanik und Flächentragwerke, TU Dresden, Nürnberger Str. 31A, Dresden, 01187, Germany; Dresden Center for Computational Materials Science, Dresden, 01062, Germany; Institut für Kontinuumsmechanik, Fakultät für Maschinenbau, Leibniz Universität Hannover, 30167 Hannover, Appelstr. 11, Germany},
      abstract={A variety of numerical approximation schemes for boundary value problems suffer from so-called locking-phenomena. It is well known that in such cases several finite element formulations exhibit poor convergence rates in the basic variables. A serious locking phenomenon can be observed in the case of anisotropic elasticity, due to high stiffness in preferred directions. The main goal of this paper is to overcome this locking problem in anisotropic hyperelasticity by introducing a novel mixed variational framework. Therefore we split the strain energy into two main parts, an isotropic and an anisotropic part. For the isotropic part we can apply different well-established approximation schemes and for the anisotropic part we apply a constant approximation of the deformation gradient or the right Cauchy–Green tensor. This additional constraint is attached to the strain energy function by a second-order tensorial Lagrange-multiplier, governed by a Simplified Kinematic for the Anisotropic part. As a matter of fact, for the tested boundary value problems the SKA-element based on quadratic ansatz functions for the displacements, performs excellent and behaves more robust than competitive formulations. © 2016 Elsevier B.V.},
      author_keywords={Anisotropic hyperelasticity; Lagrange-multiplier; Mixed finite elements; SKA-element},
      document_type={Article},
      source={Scopus},
      }

  • From Fluorine to Fluorene—A Route to Thermally Stable aza-BODIPYs for Organic Solar Cell Application
    • M. Lorenz-Rothe, K. S. Schellhammer, T. Jägeler-Hoheisel, R. Meerheim, S. Kraner, M. P. Hein, C. Schünemann, M. L. Tietze, M. Hummert, F. Ortmann, G. Cuniberti, C. Körner, K. Leo
    • Advanced Electronic Materials 2, 1600152 (2016)
    • DOI   Abstract  

      Despite favorable absorption characteristics, borondipyrromethenes (BODIPYs) often lack thermal stability preventing their application in vacuum-processed organic solar cells. In this paper, the replacement of the BF2 unit by borafluorene as a new functionalization strategy for this molecule class is explored. This approach is applied to a set of prototype molecules and demonstrates improved thermal stability, strong absorption in the red and near-infrared region of the sun spectrum, as well as excellent solar cell performance. Synthesis is realized from free ligands via complexation with 9-chloro-9-borafluorene giving high yields up to 81%. Planar heterojunction cells of these complexes exhibit high fill factors of more than 70%. Bulk heterojunction solar cells with C60 are optimized yielding power conversion efficiencies up to 4.5%, rendering the investigated prototype compounds highly competitive among other NIR-absorbing small-molecule donor materials. Comprehensive experimental material characterization and solar cell analysis are carried out, and the results are discussed together with simulations of molecular properties. Based on this analysis, additional performance improvements are proposed by engineering the intramolecular steric interactions towards further red-shifted absorption. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

      @ARTICLE{Lorenz-Rothe2016,
      author={Lorenz-Rothe, M. and Schellhammer, K.S. and Jägeler-Hoheisel, T. and Meerheim, R. and Kraner, S. and Hein, M.P. and Schünemann, C. and Tietze, M.L. and Hummert, M. and Ortmann, F. and Cuniberti, G. and Körner, C. and Leo, K.},
      title={From Fluorine to Fluorene—A Route to Thermally Stable aza-BODIPYs for Organic Solar Cell Application},
      journal={Advanced Electronic Materials},
      year={2016},
      volume={2},
      number={10},
      doi={10.1002/aelm.201600152},
      art_number={1600152},
      note={cited By 17},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84985930629&doi=10.1002%2faelm.201600152&partnerID=40&md5=e5fae036d105fe2c42f165632b0013a6},
      affiliation={Institut für Angewandte Photophysik, Technische Universität Dresden, Dresden, 01062, Germany; Institute for Materials Science, Dresden Center for Computational Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, 01062, Germany; NOVALED GmbH, Tatzberg 49, Dresden, 01307, Germany},
      abstract={Despite favorable absorption characteristics, borondipyrromethenes (BODIPYs) often lack thermal stability preventing their application in vacuum-processed organic solar cells. In this paper, the replacement of the BF2 unit by borafluorene as a new functionalization strategy for this molecule class is explored. This approach is applied to a set of prototype molecules and demonstrates improved thermal stability, strong absorption in the red and near-infrared region of the sun spectrum, as well as excellent solar cell performance. Synthesis is realized from free ligands via complexation with 9-chloro-9-borafluorene giving high yields up to 81%. Planar heterojunction cells of these complexes exhibit high fill factors of more than 70%. Bulk heterojunction solar cells with C60 are optimized yielding power conversion efficiencies up to 4.5%, rendering the investigated prototype compounds highly competitive among other NIR-absorbing small-molecule donor materials. Comprehensive experimental material characterization and solar cell analysis are carried out, and the results are discussed together with simulations of molecular properties. Based on this analysis, additional performance improvements are proposed by engineering the intramolecular steric interactions towards further red-shifted absorption. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim},
      author_keywords={BODIPY; near-infrared absorbers; organic solar cells; thermal stability; vacuum deposition},
      document_type={Article},
      source={Scopus},
      }

  • Numerical modeling of fluid–structure interaction in arteries with anisotropic polyconvex hyperelastic and anisotropic viscoelastic material models at finite strains
    • D. Balzani, S. Deparis, S. Fausten, D. Forti, A. Heinlein, A. Klawonn, A. Quarteroni, O. Rheinbach, J. Schröder
    • International Journal for Numerical Methods in Biomedical Engineering 32, e02756 (2016)
    • DOI   Abstract  

      The accurate prediction of transmural stresses in arterial walls requires on the one hand robust and efficient numerical schemes for the solution of boundary value problems including fluid–structure interactions and on the other hand the use of a material model for the vessel wall that is able to capture the relevant features of the material behavior. One of the main contributions of this paper is the application of a highly nonlinear, polyconvex anisotropic structural model for the solid in the context of fluid–structure interaction, together with a suitable discretization. Additionally, the influence of viscoelasticity is investigated. The fluid–structure interaction problem is solved using a monolithic approach; that is, the nonlinear system is solved (after time and space discretizations) as a whole without splitting among its components. The linearized block systems are solved iteratively using parallel domain decomposition preconditioners. A simple – but nonsymmetric – curved geometry is proposed that is demonstrated to be suitable as a benchmark testbed for fluid–structure interaction simulations in biomechanics where nonlinear structural models are used. Based on the curved benchmark geometry, the influence of different material models, spatial discretizations, and meshes of varying refinement is investigated. It turns out that often-used standard displacement elements with linear shape functions are not sufficient to provide good approximations of the arterial wall stresses, whereas for standard displacement elements or F-bar formulations with quadratic shape functions, suitable results are obtained. For the time discretization, a second-order backward differentiation formula scheme is used. It is shown that the curved geometry enables the analysis of non-rotationally symmetric distributions of the mechanical fields. For instance, the maximal shear stresses in the fluid–structure interface are found to be higher in the inner curve that corresponds to clinical observations indicating a high plaque nucleation probability at such locations. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

      @ARTICLE{Balzani2016,
      author={Balzani, D. and Deparis, S. and Fausten, S. and Forti, D. and Heinlein, A. and Klawonn, A. and Quarteroni, A. and Rheinbach, O. and Schröder, J.},
      title={Numerical modeling of fluid–structure interaction in arteries with anisotropic polyconvex hyperelastic and anisotropic viscoelastic material models at finite strains},
      journal={International Journal for Numerical Methods in Biomedical Engineering},
      year={2016},
      volume={32},
      number={10},
      doi={10.1002/cnm.2756},
      art_number={e02756},
      note={cited By 17},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84989223260&doi=10.1002%2fcnm.2756&partnerID=40&md5=698db88225dedc8c186dcff4c7b13b08},
      affiliation={Institute of Mechanics and Shell Structures and Dresden Center for Computational Materials Science, Technical University Dresden, Dresden, 01062, Germany; Modeling and Scientific Computing, MATHICSE – EPFL, Avenue Piccard, Station 8, Lausanne, 1015, Switzerland; Institute of Mechanics, Department of Engineering, University of Duisburg-Essen, Universitätsstraße 15, Essen, 45141, Germany; Mathematisches Institut, Universität zu Köln, Weyertal 86-90, Köln, 50931, Germany; MOX, Politecnico di Milano, via Bonardi 9, Milan, 20133, Italy; Institute of Numerical Mathematics and Optimization, Technische Universität Bergakademie Freiberg, Akademiestraße 6, Freiberg, 09599, Germany},
      abstract={The accurate prediction of transmural stresses in arterial walls requires on the one hand robust and efficient numerical schemes for the solution of boundary value problems including fluid–structure interactions and on the other hand the use of a material model for the vessel wall that is able to capture the relevant features of the material behavior. One of the main contributions of this paper is the application of a highly nonlinear, polyconvex anisotropic structural model for the solid in the context of fluid–structure interaction, together with a suitable discretization. Additionally, the influence of viscoelasticity is investigated. The fluid–structure interaction problem is solved using a monolithic approach; that is, the nonlinear system is solved (after time and space discretizations) as a whole without splitting among its components. The linearized block systems are solved iteratively using parallel domain decomposition preconditioners. A simple – but nonsymmetric – curved geometry is proposed that is demonstrated to be suitable as a benchmark testbed for fluid–structure interaction simulations in biomechanics where nonlinear structural models are used. Based on the curved benchmark geometry, the influence of different material models, spatial discretizations, and meshes of varying refinement is investigated. It turns out that often-used standard displacement elements with linear shape functions are not sufficient to provide good approximations of the arterial wall stresses, whereas for standard displacement elements or F-bar formulations with quadratic shape functions, suitable results are obtained. For the time discretization, a second-order backward differentiation formula scheme is used. It is shown that the curved geometry enables the analysis of non-rotationally symmetric distributions of the mechanical fields. For instance, the maximal shear stresses in the fluid–structure interface are found to be higher in the inner curve that corresponds to clinical observations indicating a high plaque nucleation probability at such locations. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.},
      author_keywords={almost incompressible; anisotropic; domain decomposition; monolithic fluid–structure interaction; parallel; polyconvex hyperelasticity},
      document_type={Article},
      source={Scopus},
      }

  • Discrete polygonal supramolecular architectures of isocytosine-based Pt(ii) complexes at the solution/graphite interface
    • M. El Garah, S. Sinn, A. Dianat, A. Santana-Bonilla, R. Gutierrez, L. De Cola, G. Cuniberti, A. Ciesielski, P. Samorì
    • Chemical Communications 52, 11163-11166 (2016)
    • DOI   Abstract  

      Polygonal supramolecular architectures of a Pt(ii) complex including trimers, tetramers, pentamers and hexamers were self-assembled via hydrogen bonding between isocytosine moieties; their structure at the solid/liquid interface was unravelled by in situ scanning tunneling microscopy imaging. Density functional theory calculations provided in-depth insight into the thermodynamics of their formation by exploring the different energy contributions attributed to the molecular self-assembly and adsorption processes. © The Royal Society of Chemistry.

      @ARTICLE{ElGarah201611163,
      author={El Garah, M. and Sinn, S. and Dianat, A. and Santana-Bonilla, A. and Gutierrez, R. and De Cola, L. and Cuniberti, G. and Ciesielski, A. and Samorì, P.},
      title={Discrete polygonal supramolecular architectures of isocytosine-based Pt(ii) complexes at the solution/graphite interface},
      journal={Chemical Communications},
      year={2016},
      volume={52},
      number={74},
      pages={11163-11166},
      doi={10.1039/c6cc05087e},
      note={cited By 7},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987597566&doi=10.1039%2fc6cc05087e&partnerID=40&md5=e268368e394f7d867d365edc6713d3b8},
      affiliation={Laboratoire de Nanochimie, ISIS, icFRC, Université de Strasbourg, CNRS, 8 allée Gaspard Monge, Strasbourg, 67000, France; Laboratoire de Chimie et des Biomatériaux Supramoléculaires, ISIS, icFRC, Université de Strasbourg, CNRS, 8 allée Gaspard Monge, Strasbourg, 67000, France; Institute for Materials Sciences, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany},
      abstract={Polygonal supramolecular architectures of a Pt(ii) complex including trimers, tetramers, pentamers and hexamers were self-assembled via hydrogen bonding between isocytosine moieties; their structure at the solid/liquid interface was unravelled by in situ scanning tunneling microscopy imaging. Density functional theory calculations provided in-depth insight into the thermodynamics of their formation by exploring the different energy contributions attributed to the molecular self-assembly and adsorption processes. © The Royal Society of Chemistry.},
      document_type={Article},
      source={Scopus},
      }

  • Synthesis of NBN-Type Zigzag-Edged Polycyclic Aromatic Hydrocarbons: 1,9-Diaza-9a-boraphenalene as a Structural Motif
    • X. Wang, F. Zhang, K. S. Schellhammer, P. Machata, F. Ortmann, G. Cuniberti, Y. Fu, J. Hunger, R. Tang, A. A. Popov, R. Berger, K. Müllen, X. Feng
    • Journal of the American Chemical Society 138, 11606-11615 (2016)
    • DOI   Abstract  

      A novel class of dibenzo-fused 1,9-diaza-9a-boraphenalenes featuring zigzag edges with a nitrogen-boron-nitrogen bonding pattern named NBN-dibenzophenalenes (NBN-DBPs) has been synthesized. Alternating nitrogen and boron atoms impart high chemical stability to these zigzag-edged polycyclic aromatic hydrocarbons (PAHs), and this motif even allows for postsynthetic modifications, as demonstrated here through electrophilic bromination and subsequent palladium-catalyzed cross-coupling reactions. Upon oxidation, as a typical example, NBN-DBP 5a was nearly quantitatively converted to σ-dimer 5a-2 through an open-shell intermediate, as indicated by UV-vis-NIR absorption spectroscopy and electron paramagnetic resonance spectroscopy corroborated by spectroscopic calculations, as well as 2D NMR spectra analyses. In situ spectroelectrochemistry was used to confirm the formation process of the dimer radical cation 5a-2•+. Finally, the developed new synthetic strategy could also be applied to obtain π-extended NBN-dibenzoheptazethrene (NBN-DBHZ), representing an efficient pathway toward NBN-doped zigzag-edged graphene nanoribbons. © 2016 American Chemical Society.

      @ARTICLE{Wang201611606,
      author={Wang, X. and Zhang, F. and Schellhammer, K.S. and Machata, P. and Ortmann, F. and Cuniberti, G. and Fu, Y. and Hunger, J. and Tang, R. and Popov, A.A. and Berger, R. and Müllen, K. and Feng, X.},
      title={Synthesis of NBN-Type Zigzag-Edged Polycyclic Aromatic Hydrocarbons: 1,9-Diaza-9a-boraphenalene as a Structural Motif},
      journal={Journal of the American Chemical Society},
      year={2016},
      volume={138},
      number={36},
      pages={11606-11615},
      doi={10.1021/jacs.6b04445},
      note={cited By 61},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987858841&doi=10.1021%2fjacs.6b04445&partnerID=40&md5=b16b008fe412cf4d1ec708768a2f3f66},
      affiliation={School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, China; Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden (Cfaed), Department of Chemistry and Food Chemistry, Technische Universität Dresden, Dresden, 01062, Germany; Center of Spectroelectrochemistry, Department of Electrochemistry and Conducting Polymers, Leibniz Institute for Solid State and Materials Research, Dresden, 01069, Germany; Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany},
      abstract={A novel class of dibenzo-fused 1,9-diaza-9a-boraphenalenes featuring zigzag edges with a nitrogen-boron-nitrogen bonding pattern named NBN-dibenzophenalenes (NBN-DBPs) has been synthesized. Alternating nitrogen and boron atoms impart high chemical stability to these zigzag-edged polycyclic aromatic hydrocarbons (PAHs), and this motif even allows for postsynthetic modifications, as demonstrated here through electrophilic bromination and subsequent palladium-catalyzed cross-coupling reactions. Upon oxidation, as a typical example, NBN-DBP 5a was nearly quantitatively converted to σ-dimer 5a-2 through an open-shell intermediate, as indicated by UV-vis-NIR absorption spectroscopy and electron paramagnetic resonance spectroscopy corroborated by spectroscopic calculations, as well as 2D NMR spectra analyses. In situ spectroelectrochemistry was used to confirm the formation process of the dimer radical cation 5a-2•+. Finally, the developed new synthetic strategy could also be applied to obtain π-extended NBN-dibenzoheptazethrene (NBN-DBHZ), representing an efficient pathway toward NBN-doped zigzag-edged graphene nanoribbons. © 2016 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Impact of incomplete metal coverage on the electrical properties of metal-CNT contacts: A large-scale ab initio study
    • A. Fediai, D. A. Ryndyk, G. Seifert, S. Mothes, M. Schroter, M. Claus, G. Cuniberti
    • Applied Physics Letters 109, 103101 (2016)
    • DOI   Abstract  

      Using a dedicated combination of the non-equilibrium Green function formalism and large-scale density functional theory calculations, we investigated how incomplete metal coverage influences two of the most important electrical properties of carbon nanotube (CNT)-based transistors: contact resistance and its scaling with contact length, and maximum current. These quantities have been derived from parameter-free simulations of atomic systems that are as close as possible to experimental geometries. Physical mechanisms that govern these dependences have been identified for various metals, representing different CNT-metal interaction strengths from chemisorption to physisorption. Our results pave the way for an application-oriented design of CNT-metal contacts. © 2016 Author(s).

      @ARTICLE{Fediai2016,
      author={Fediai, A. and Ryndyk, D.A. and Seifert, G. and Mothes, S. and Schroter, M. and Claus, M. and Cuniberti, G.},
      title={Impact of incomplete metal coverage on the electrical properties of metal-CNT contacts: A large-scale ab initio study},
      journal={Applied Physics Letters},
      year={2016},
      volume={109},
      number={10},
      doi={10.1063/1.4962439},
      art_number={103101},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84986309336&doi=10.1063%2f1.4962439&partnerID=40&md5=38399140f1756dab83e8dfd77afe5b16},
      affiliation={Institute for Materials Science, Max Bergman Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Theoretical Chemistry, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science, TU Dresden, Dresden, 01062, Germany; Department of Electron Devices and Integrated Circuits, TU Dresden, Dresden, 01062, Germany},
      abstract={Using a dedicated combination of the non-equilibrium Green function formalism and large-scale density functional theory calculations, we investigated how incomplete metal coverage influences two of the most important electrical properties of carbon nanotube (CNT)-based transistors: contact resistance and its scaling with contact length, and maximum current. These quantities have been derived from parameter-free simulations of atomic systems that are as close as possible to experimental geometries. Physical mechanisms that govern these dependences have been identified for various metals, representing different CNT-metal interaction strengths from chemisorption to physisorption. Our results pave the way for an application-oriented design of CNT-metal contacts. © 2016 Author(s).},
      document_type={Article},
      source={Scopus},
      }

  • Empirical transport model of strained CNT transistors used for sensor applications
    • C. Wagner, J. Schuster, T. Gessner
    • Journal of Computational Electronics 15, 881-890 (2016)
    • DOI   Abstract  

      We present an empirical model for the near-ballistic transport in carbon nanotube (CNT) transistors used as strain sensors. This model describes the intrinsic effect of strain on the transport in CNTs by taking into account phonon scattering and thermally activated charge carriers. As this model relies on a semiempirical description of the electronic bands, different levels of electronic structure calculations can be used as input. The results show that the electronic structure of strained single-walled CNTs with a radius larger than 0.7 nm can be described by a fully analytical model in the sensing regime. For CNTs with smaller diameter, parameterized data from electronic structure calculations can be used for the model. Depending on the type of CNTs, the conductance can vary by several orders of magnitude when strain is applied, which is consistent with the current literature. Further, we demonstrate the tuning of the sensor by an external gate which allows shifting the signal amplitude. These parameters have to be balanced to get good sensing properties. The impact of (semi-)metallic CNTs on the sensor performance is evaluated, too. Metallic CNTs have to be avoided in order to construct working sensing devices. Due to its basically analytical nature, the transport model can be evolved towards a compact model for circuit simulations. © 2016, Springer Science+Business Media New York.

      @ARTICLE{Wagner2016881,
      author={Wagner, C. and Schuster, J. and Gessner, T.},
      title={Empirical transport model of strained CNT transistors used for sensor applications},
      journal={Journal of Computational Electronics},
      year={2016},
      volume={15},
      number={3},
      pages={881-890},
      doi={10.1007/s10825-016-0823-4},
      note={cited By 9},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84964328546&doi=10.1007%2fs10825-016-0823-4&partnerID=40&md5=54ec24f3bf1f2602429166ef6443840a},
      affiliation={Technische Universität Chemnitz, Center for Microtechnologies, Reichenhainer Straße 70, Chemnitz, 09126, Germany; Fraunhofer Institute for Electronic Nano Systems (ENAS), Techologiecampus 3, Chemnitz, 09126, Germany; Dresden Center for Computational Materials Science (DCCMS), Dresden, TU, Germany},
      abstract={We present an empirical model for the near-ballistic transport in carbon nanotube (CNT) transistors used as strain sensors. This model describes the intrinsic effect of strain on the transport in CNTs by taking into account phonon scattering and thermally activated charge carriers. As this model relies on a semiempirical description of the electronic bands, different levels of electronic structure calculations can be used as input. The results show that the electronic structure of strained single-walled CNTs with a radius larger than 0.7 nm can be described by a fully analytical model in the sensing regime. For CNTs with smaller diameter, parameterized data from electronic structure calculations can be used for the model. Depending on the type of CNTs, the conductance can vary by several orders of magnitude when strain is applied, which is consistent with the current literature. Further, we demonstrate the tuning of the sensor by an external gate which allows shifting the signal amplitude. These parameters have to be balanced to get good sensing properties. The impact of (semi-)metallic CNTs on the sensor performance is evaluated, too. Metallic CNTs have to be avoided in order to construct working sensing devices. Due to its basically analytical nature, the transport model can be evolved towards a compact model for circuit simulations. © 2016, Springer Science+Business Media New York.},
      author_keywords={Carbon nanotubes; Density functional theory; Empiric modeling; Nanoelectromechanical systems (NEMS); Near-ballistic transport; Strain sensor},
      document_type={Article},
      source={Scopus},
      }

  • Anisotropic Thermoelectric Response in Two-Dimensional Puckered Structures
    • L. Medrano Sandonas, D. Teich, R. Gutierrez, T. Lorenz, A. Pecchia, G. Seifert, G. Cuniberti
    • Journal of Physical Chemistry C 120, 18841-18849 (2016)
    • DOI   Abstract  

      Two-dimensional semiconductor materials with puckered structure offer a novel playground to implement nanoscale thermoelectric, electronic, and optoelectronic devices with improved functionality. Using a combination of approaches to compute the electronic and phonon band structures with Green's function based transport techniques, we address the thermoelectric performance of phosphorene, arsenene, and SnS monolayers. In particular, we study the influence of anisotropy in the electronic and phononic transport properties and its impact on the thermoelectric figure of merit ZT. Our results show no strong electronic anisotropy, but a strong thermal one, the effect being most pronounced in the case of SnS monolayers. This material also displays the largest figure of merit at room temperature for both transport directions, zigzag (ZT ∼ 0.95) and armchair (ZT ∼ 1.6), thus hinting at the high potential of these new materials in thermoelectric applications. © 2016 American Chemical Society.

      @ARTICLE{MedranoSandonas201618841,
      author={Medrano Sandonas, L. and Teich, D. and Gutierrez, R. and Lorenz, T. and Pecchia, A. and Seifert, G. and Cuniberti, G.},
      title={Anisotropic Thermoelectric Response in Two-Dimensional Puckered Structures},
      journal={Journal of Physical Chemistry C},
      year={2016},
      volume={120},
      number={33},
      pages={18841-18849},
      doi={10.1021/acs.jpcc.6b04969},
      note={cited By 55},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984605015&doi=10.1021%2facs.jpcc.6b04969&partnerID=40&md5=a2fcf002c0e7e8a6f48e2e4f71106313},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden, 01062, Germany; Institut für Physikalische Chemie und Elektrochemie, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, 01187, Germany; Consiglio Nazionale Delle Ricerche, ISMN, Via Salaria km 29.6, Monterotondo, Rome, 00017, Italy},
      abstract={Two-dimensional semiconductor materials with puckered structure offer a novel playground to implement nanoscale thermoelectric, electronic, and optoelectronic devices with improved functionality. Using a combination of approaches to compute the electronic and phonon band structures with Green's function based transport techniques, we address the thermoelectric performance of phosphorene, arsenene, and SnS monolayers. In particular, we study the influence of anisotropy in the electronic and phononic transport properties and its impact on the thermoelectric figure of merit ZT. Our results show no strong electronic anisotropy, but a strong thermal one, the effect being most pronounced in the case of SnS monolayers. This material also displays the largest figure of merit at room temperature for both transport directions, zigzag (ZT ∼ 0.95) and armchair (ZT ∼ 1.6), thus hinting at the high potential of these new materials in thermoelectric applications. © 2016 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • The modular approach enables a fully ab initio simulation of the contacts between 3D and 2D materials
    • A. Fediai, D. A. Ryndyk, G. Cuniberti
    • Journal of Physics Condensed Matter 28, 395303 (2016)
    • DOI   Abstract  

      Up to now, the electrical properties of the contacts between 3D metals and 2D materials have never been computed at a fully ab initio level due to the huge number of atomic orbitals involved in a current path from an electrode to a pristine 2D material. As a result, there are still numerous open questions and controversial theories on the electrical properties of systems with 3D/2D interfaces - for example, the current path and the contact length scalability. Our work provides a first-principles solution to this long-standing problem with the use of the modular approach, a method which rigorously combines a Green function formalism with the density functional theory (DFT) for this particular contact type. The modular approach is a general approach valid for any 3D/2D contact. As an example, we apply it to the most investigated among 3D/2D contacts - metal/graphene contacts - and show its abilities and consistency by comparison with existing experimental data. As it is applicable to any 3D/2D interface, the modular approach allows the engineering of 3D/2D contacts with the pre-defined electrical properties. © 2016 IOP Publishing Ltd.

      @ARTICLE{Fediai2016,
      author={Fediai, A. and Ryndyk, D.A. and Cuniberti, G.},
      title={The modular approach enables a fully ab initio simulation of the contacts between 3D and 2D materials},
      journal={Journal of Physics Condensed Matter},
      year={2016},
      volume={28},
      number={39},
      doi={10.1088/0953-8984/28/39/395303},
      art_number={395303},
      note={cited By 0},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988416283&doi=10.1088%2f0953-8984%2f28%2f39%2f395303&partnerID=40&md5=678d8b814eb212964d2e71b1244f1321},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={Up to now, the electrical properties of the contacts between 3D metals and 2D materials have never been computed at a fully ab initio level due to the huge number of atomic orbitals involved in a current path from an electrode to a pristine 2D material. As a result, there are still numerous open questions and controversial theories on the electrical properties of systems with 3D/2D interfaces - for example, the current path and the contact length scalability. Our work provides a first-principles solution to this long-standing problem with the use of the modular approach, a method which rigorously combines a Green function formalism with the density functional theory (DFT) for this particular contact type. The modular approach is a general approach valid for any 3D/2D contact. As an example, we apply it to the most investigated among 3D/2D contacts - metal/graphene contacts - and show its abilities and consistency by comparison with existing experimental data. As it is applicable to any 3D/2D interface, the modular approach allows the engineering of 3D/2D contacts with the pre-defined electrical properties. © 2016 IOP Publishing Ltd.},
      author_keywords={contact length scaling; contacts; DFT; extended contacts; grapheme; Green function method; two-dimensional materials},
      document_type={Article},
      source={Scopus},
      }

  • A microscopic field theoretical approach for active systems
    • F. Alaimo, S. Praetorius, A. Voigt
    • New Journal of Physics 18, 083008 (2016)
    • DOI   Abstract  

      We consider a microscopic modeling approach for active systems. The approach extends the phase field crystal (PFC) model and allows us to describe generic properties of active systems within a continuum model. The approach is validated by reproducing results obtained with corresponding agent-based and microscopic phase field models. We consider binary collisions, collective motion and vortex formation. For larger numbers of particles we analyze the coarsening process in active crystals and identify giant number fluctuation in a cluster formation process. © 2016 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

      @ARTICLE{Alaimo2016,
      author={Alaimo, F. and Praetorius, S. and Voigt, A.},
      title={A microscopic field theoretical approach for active systems},
      journal={New Journal of Physics},
      year={2016},
      volume={18},
      number={8},
      doi={10.1088/1367-2630/18/8/083008},
      art_number={083008},
      note={cited By 17},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983376705&doi=10.1088%2f1367-2630%2f18%2f8%2f083008&partnerID=40&md5=aa07a163948dabb1947160df1fa34947},
      affiliation={Institut für Wissenschaftliches Rechnen, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Center for Systems Biology Dresden (CSBD), Pfotenhauerstr. 108, Dresden, 01307, Germany},
      abstract={We consider a microscopic modeling approach for active systems. The approach extends the phase field crystal (PFC) model and allows us to describe generic properties of active systems within a continuum model. The approach is validated by reproducing results obtained with corresponding agent-based and microscopic phase field models. We consider binary collisions, collective motion and vortex formation. For larger numbers of particles we analyze the coarsening process in active crystals and identify giant number fluctuation in a cluster formation process. © 2016 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.},
      author_keywords={Active crystals; Active systems; Cluster formation; Phase field crystal modeling},
      document_type={Article},
      source={Scopus},
      }

  • Influence of the synthesis conditions of gold nanoparticles on the structure and architectonics of dipeptide composites
    • A. I. Loskutov, O. A. Guskova, S. N. Grigoriev, V. B. Oshurko, A. V. Tarasiuk, O. Y. Uryupina
    • Journal of Nanoparticle Research 18, 239 (2016)
    • DOI   Abstract  

      A wide variety of peptides and their natural ability to self-assemble makes them very promising candidates for the fabrication of solid-state devices based on nano- and mesocrystals. In this work, we demonstrate an approach to form peptide composite layers with gold nanoparticles through in situ reduction of chloroauric acid trihydrate by dipeptide and/or dipeptide/formaldehyde mixture in the presence of potassium carbonate at different ratios of components. Appropriate composition of components for the synthesis of highly stable gold colloidal dispersion with particle size of 34–36 nm in dipeptide/formaldehyde solution is formulated. Infrared spectroscopy results indicate that dipeptide participates in the reduction process, conjugation with gold nanoparticles and the self-assembly in 2D, which accompanied by changing peptide chain conformations. The structure and morphology of the peptide composite solid layers with gold nanoparticles on gold, mica and silica surfaces are characterized by atomic force microscopy. In these experiments, the flat particles, dendrites, chains, mesocrystals and Janus particles are observed depending on the solution composition and the substrate/interface used. The latter aspect is studied on the molecular level using computer simulations of individual peptide chains on gold, mica and silica surfaces. © 2016, Springer Science+Business Media Dordrecht.

      @ARTICLE{Loskutov2016,
      author={Loskutov, A.I. and Guskova, O.A. and Grigoriev, S.N. and Oshurko, V.B. and Tarasiuk, A.V. and Uryupina, O.Y.},
      title={Influence of the synthesis conditions of gold nanoparticles on the structure and architectonics of dipeptide composites},
      journal={Journal of Nanoparticle Research},
      year={2016},
      volume={18},
      number={8},
      doi={10.1007/s11051-016-3548-1},
      art_number={239},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982253542&doi=10.1007%2fs11051-016-3548-1&partnerID=40&md5=1f013b31c21503341a01db8f5b1d42ae},
      affiliation={Moscow State Technological University STANKIN, Vadkovskii per. 1, Moscow, 127994, Russian Federation; Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, Dresden, 01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, 01062, Germany; FSBI “Zakusov Institute of Pharmacology”, Russian Academy of Medical Sciences, Baltiyskaya str. 8, Moscow, 125315, Russian Federation; Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119991, Russian Federation},
      abstract={A wide variety of peptides and their natural ability to self-assemble makes them very promising candidates for the fabrication of solid-state devices based on nano- and mesocrystals. In this work, we demonstrate an approach to form peptide composite layers with gold nanoparticles through in situ reduction of chloroauric acid trihydrate by dipeptide and/or dipeptide/formaldehyde mixture in the presence of potassium carbonate at different ratios of components. Appropriate composition of components for the synthesis of highly stable gold colloidal dispersion with particle size of 34–36 nm in dipeptide/formaldehyde solution is formulated. Infrared spectroscopy results indicate that dipeptide participates in the reduction process, conjugation with gold nanoparticles and the self-assembly in 2D, which accompanied by changing peptide chain conformations. The structure and morphology of the peptide composite solid layers with gold nanoparticles on gold, mica and silica surfaces are characterized by atomic force microscopy. In these experiments, the flat particles, dendrites, chains, mesocrystals and Janus particles are observed depending on the solution composition and the substrate/interface used. The latter aspect is studied on the molecular level using computer simulations of individual peptide chains on gold, mica and silica surfaces. © 2016, Springer Science+Business Media Dordrecht.},
      author_keywords={Gold nanoparticles; Morphology; Nanocomposite; Nanoscale architechture; Peptide; Synthesis},
      document_type={Article},
      source={Scopus},
      }

  • TiO2/graphene oxide immobilized in P(VDF-TrFE) electrospun membranes with enhanced visible-light-induced photocatalytic performance
    • N. A. Almeida, P. M. Martins, S. Teixeira, J. A. Lopes da Silva, V. Sencadas, K. Kühn, G. Cuniberti, S. Lanceros-Mendez, P. A. A. P. Marques
    • Journal of Materials Science 51, 6974-6986 (2016)
    • DOI   Abstract  

      Here, we report on the electrospinning of poly(vinylidene difluoride-co-trifluoroethylene) (P(VDF-TrFE)) copolymer fibrous membranes decorated with titanium dioxide/graphene oxide (TiO2/GO). The presence of the TiO2/GO increases the photocatalytic efficiency of the nanocomposite membrane towards the degradation of methylene blue (MB) when compared with the membranes prepared with naked TiO2, in UV and particularly in the visible range. Even a low content (3 %, w/w) of TiO2/GO in the fibers yields excellent photocatalytic performance by degrading ~100 % of a MB solution after 90 min of visible light exposure. This may be attributed to a rapid electron transport and the delayed recombination of electron–hole pairs due to improved ionic interaction between titanium and carbon combined with the advantageous electric properties of the polymer, such as high polarization and dielectric constant combined with low dielectric loss. Thus, a promising system to degrade organic pollutants in aqueous or gaseous systems under visible light irradiation has been developed. © 2016, Springer Science+Business Media New York.

      @ARTICLE{Almeida20166974,
      author={Almeida, N.A. and Martins, P.M. and Teixeira, S. and Lopes da Silva, J.A. and Sencadas, V. and Kühn, K. and Cuniberti, G. and Lanceros-Mendez, S. and Marques, P.A.A.P.},
      title={TiO2/graphene oxide immobilized in P(VDF-TrFE) electrospun membranes with enhanced visible-light-induced photocatalytic performance},
      journal={Journal of Materials Science},
      year={2016},
      volume={51},
      number={14},
      pages={6974-6986},
      doi={10.1007/s10853-016-9986-4},
      note={cited By 51},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84964446480&doi=10.1007%2fs10853-016-9986-4&partnerID=40&md5=3d53f4894c8baae7d58222e60836eb41},
      affiliation={TEMA/Department of Mechanical Engineering, University of Aveiro, Aveiro, 3810-193, Portugal; Centre/Departament of Physics, University of Minho, Campus de Gualtar, Braga, 4710-057, Portugal; Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; QOPNA/Chemistry Department of Chemistry, University of Aveiro, Aveiro, 3810-193, Portugal; Dresden Center for Computational Materials Science (DCCMS), TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; BC Materials, Parque Científico y Tecnológico de Bizkaia, Derio, 48160, Spain},
      abstract={Here, we report on the electrospinning of poly(vinylidene difluoride-co-trifluoroethylene) (P(VDF-TrFE)) copolymer fibrous membranes decorated with titanium dioxide/graphene oxide (TiO2/GO). The presence of the TiO2/GO increases the photocatalytic efficiency of the nanocomposite membrane towards the degradation of methylene blue (MB) when compared with the membranes prepared with naked TiO2, in UV and particularly in the visible range. Even a low content (3 %, w/w) of TiO2/GO in the fibers yields excellent photocatalytic performance by degrading ~100 % of a MB solution after 90 min of visible light exposure. This may be attributed to a rapid electron transport and the delayed recombination of electron–hole pairs due to improved ionic interaction between titanium and carbon combined with the advantageous electric properties of the polymer, such as high polarization and dielectric constant combined with low dielectric loss. Thus, a promising system to degrade organic pollutants in aqueous or gaseous systems under visible light irradiation has been developed. © 2016, Springer Science+Business Media New York.},
      document_type={Article},
      source={Scopus},
      }

  • Temperature-Dependent Hole Mobility and Its Limit in Crystal-Phase P3HT Calculated from First Principles
    • A. Lücke, F. Ortmann, M. Panhans, S. Sanna, E. Rauls, U. Gerstmann, W. G. Schmidt
    • Journal of Physical Chemistry B 120, 5572-5580 (2016)
    • DOI   Abstract  

      We study temperature-dependent hole transport in ideal crystal-phase poly(3-hexylthiophene) (P3HT) with ab initio calculations, with the aim of estimating the maximum mobility in the limit of perfect order. To this end, the molecular transfer integrals, phonon frequencies, and electron-phonon coupling constants are obtained from density functional theory (DFT). This allows the determination of transport properties without fit parameters. The strong coupling between charge carriers and vibrations leads to strong scattering and polaronic effects that impact carrier transport. By providing an intrinsic mobility limit to ideal P3HT crystals, this work allows identification of the impact of disorder on the temperature-dependent transport in real samples. A detailed analysis of the transport-relevant phonon modes is provided that gives microscopic insight into the polaron effects and hints toward mobility optimization strategies. © 2016 American Chemical Society.

      @ARTICLE{Lücke20165572,
      author={Lücke, A. and Ortmann, F. and Panhans, M. and Sanna, S. and Rauls, E. and Gerstmann, U. and Schmidt, W.G.},
      title={Temperature-Dependent Hole Mobility and Its Limit in Crystal-Phase P3HT Calculated from First Principles},
      journal={Journal of Physical Chemistry B},
      year={2016},
      volume={120},
      number={24},
      pages={5572-5580},
      doi={10.1021/acs.jpcb.6b03598},
      note={cited By 9},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84976259447&doi=10.1021%2facs.jpcb.6b03598&partnerID=40&md5=bbc4bbaf863be37c399153f1a3961d5c},
      affiliation={Lehrstuhl für Theoretische Materialphysik, Universität Paderborn, Paderborn, 33095, Germany; Institute for Materials Science, Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01069, Germany},
      abstract={We study temperature-dependent hole transport in ideal crystal-phase poly(3-hexylthiophene) (P3HT) with ab initio calculations, with the aim of estimating the maximum mobility in the limit of perfect order. To this end, the molecular transfer integrals, phonon frequencies, and electron-phonon coupling constants are obtained from density functional theory (DFT). This allows the determination of transport properties without fit parameters. The strong coupling between charge carriers and vibrations leads to strong scattering and polaronic effects that impact carrier transport. By providing an intrinsic mobility limit to ideal P3HT crystals, this work allows identification of the impact of disorder on the temperature-dependent transport in real samples. A detailed analysis of the transport-relevant phonon modes is provided that gives microscopic insight into the polaron effects and hints toward mobility optimization strategies. © 2016 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Band structure engineering in organic semiconductors
    • M. Schwarze, W. Tress, B. Beyer, F. Gao, R. Scholz, C. Poelking, K. Ortstein, A. A. Günther, D. Kasemann, D. Andrienko, K. Leo
    • Science 352, 1446-1449 (2016)
    • DOI   Abstract  

      A key breakthrough in modern electronics was the introduction of band structure engineering, the design of almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune the band gap and band-edge energies. Implementation of this approach in organic semiconductors has been hindered by strong localization of the electronic states in these materials.We show that the influence of so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms that the ionization energies of crystalline organic semiconductors can be continuously tuned over a wide range by blending them with their halogenated derivatives. Correspondingly, the photovoltaic gap and open-circuit voltage of organic solar cells can be continuously tuned by the blending ratio of these donors.

      @ARTICLE{Schwarze20161446,
      author={Schwarze, M. and Tress, W. and Beyer, B. and Gao, F. and Scholz, R. and Poelking, C. and Ortstein, K. and Günther, A.A. and Kasemann, D. and Andrienko, D. and Leo, K.},
      title={Band structure engineering in organic semiconductors},
      journal={Science},
      year={2016},
      volume={352},
      number={6292},
      pages={1446-1449},
      doi={10.1126/science.aaf0590},
      note={cited By 140},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84975159519&doi=10.1126%2fscience.aaf0590&partnerID=40&md5=69b9ba4bf666313ea65340ea98583f3d},
      affiliation={Institut für Angewandte Photophysik, Technische Universität Dresden, Dresden, 01069, Germany; Biomolecular and Organic Electronics, IFM, Linköping University, Linköping, 58183, Sweden; Fraunhofer Institute for Electron Beam, Plasma Technology and COMEDD, Dresden, 01109, Germany; Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany; Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany; Laboratory of Photonics and Interfaces, Swiss Federal Institute of Technology (EPFL), Station 6, Lausanne, CH 1015, Switzerland},
      abstract={A key breakthrough in modern electronics was the introduction of band structure engineering, the design of almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune the band gap and band-edge energies. Implementation of this approach in organic semiconductors has been hindered by strong localization of the electronic states in these materials.We show that the influence of so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms that the ionization energies of crystalline organic semiconductors can be continuously tuned over a wide range by blending them with their halogenated derivatives. Correspondingly, the photovoltaic gap and open-circuit voltage of organic solar cells can be continuously tuned by the blending ratio of these donors.},
      document_type={Article},
      source={Scopus},
      }

  • Bézier extraction and adaptive refinement of truncated hierarchical NURBS
    • P. Hennig, S. Müller, M. Kästner
    • Computer Methods in Applied Mechanics and Engineering 305, 316-339 (2016)
    • DOI   Abstract  

      This contribution presents Bézier extraction of truncated hierarchical B-splines and the application of the approach to adaptive isogeometric analysis. The developed procedures allow for the implementation of hierarchical B-splines and NURBS without the need for an explicit truncation of the basis. Moreover, standard procedures of adaptive finite element analysis for error estimation and marking of elements are directly applicable due to the strict use of an element viewpoint. Starting from a multi-level nested mesh that results from uniform h-refinement, standard Bézier extraction is applied to active elements that contribute to the hierarchical approximation. This results in a multi-level system of equations without communication between individual hierarchy levels. A hierarchical subdivision operator is developed to recover this communication by transforming the multi-level system of equations into a hierarchical system of equations. It is demonstrated that this approach implicitly defines the truncated hierarchical basis in terms of a simple matrix multiplication. In this way, the implementation effort is reduced to a minimum as shape function routines and Bézier extraction procedures remain unchanged compared to standard isogeometric analysis. The convergence and the computational efficiency of the approach are examined in three different demonstration problems of heat conduction, linear elasticity, and the phase-field modelling of brittle fracture. © 2016 Elsevier B.V.

      @ARTICLE{Hennig2016316,
      author={Hennig, P. and Müller, S. and Kästner, M.},
      title={Bézier extraction and adaptive refinement of truncated hierarchical NURBS},
      journal={Computer Methods in Applied Mechanics and Engineering},
      year={2016},
      volume={305},
      pages={316-339},
      doi={10.1016/j.cma.2016.03.009},
      note={cited By 48},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963646021&doi=10.1016%2fj.cma.2016.03.009&partnerID=40&md5=4f04e09097f03572ebc1ba28fade9710},
      affiliation={Institute of Solid Mechanics, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany},
      abstract={This contribution presents Bézier extraction of truncated hierarchical B-splines and the application of the approach to adaptive isogeometric analysis. The developed procedures allow for the implementation of hierarchical B-splines and NURBS without the need for an explicit truncation of the basis. Moreover, standard procedures of adaptive finite element analysis for error estimation and marking of elements are directly applicable due to the strict use of an element viewpoint. Starting from a multi-level nested mesh that results from uniform h-refinement, standard Bézier extraction is applied to active elements that contribute to the hierarchical approximation. This results in a multi-level system of equations without communication between individual hierarchy levels. A hierarchical subdivision operator is developed to recover this communication by transforming the multi-level system of equations into a hierarchical system of equations. It is demonstrated that this approach implicitly defines the truncated hierarchical basis in terms of a simple matrix multiplication. In this way, the implementation effort is reduced to a minimum as shape function routines and Bézier extraction procedures remain unchanged compared to standard isogeometric analysis. The convergence and the computational efficiency of the approach are examined in three different demonstration problems of heat conduction, linear elasticity, and the phase-field modelling of brittle fracture. © 2016 Elsevier B.V.},
      author_keywords={Adaptivity; Bézier extraction; Hierarchical B-splines; Isogeometric analysis; Phase-field modelling},
      document_type={Article},
      source={Scopus},
      }

  • Synergistically Enhanced Polysulfide Chemisorption Using a Flexible Hybrid Separator with N and S Dual-Doped Mesoporous Carbon Coating for Advanced Lithium-Sulfur Batteries
    • J. Balach, H. K. Singh, S. Gomoll, T. Jaumann, M. Klose, S. Oswald, M. Richter, J. Eckert, L. Giebeler
    • ACS Applied Materials and Interfaces 8, 14586-14595 (2016)
    • DOI   Abstract  

      Because of the outstanding high theoretical specific energy density of 2600 Wh kg-1, the lithium-sulfur (Li-S) battery is regarded as a promising candidate for post lithium-ion battery systems eligible to meet the forthcoming market requirements. However, its commercialization on large scale is thwarted by fast capacity fading caused by the Achilles' heel of Li-S systems: the polysulfide shuttle. Here, we merge the physical features of carbon-coated separators and the unique chemical properties of N and S codoped mesoporous carbon to create a functional hybrid separator with superior polysulfide affinity and electrochemical benefits. DFT calculations revealed that carbon materials with N and S codoping possess a strong binding energy to high-order polysulfide species, which is essential to keep the active material in the cathode side. As a result of the synergistic effect of N, S dual-doping, an advanced Li-S cell with high specific capacity and ultralow capacity degradation of 0.041% per cycle is achieved. Pushing our simple-designed and scalable cathode to a highly increased sulfur loading of 5.4 mg cm-2, the Li-S cell with the functional hybrid separator can deliver a remarkable areal capacity of 5.9 mAh cm-2, which is highly favorable for practical applications. © 2016 American Chemical Society.

      @ARTICLE{Balach201614586,
      author={Balach, J. and Singh, H.K. and Gomoll, S. and Jaumann, T. and Klose, M. and Oswald, S. and Richter, M. and Eckert, J. and Giebeler, L.},
      title={Synergistically Enhanced Polysulfide Chemisorption Using a Flexible Hybrid Separator with N and S Dual-Doped Mesoporous Carbon Coating for Advanced Lithium-Sulfur Batteries},
      journal={ACS Applied Materials and Interfaces},
      year={2016},
      volume={8},
      number={23},
      pages={14586-14595},
      doi={10.1021/acsami.6b03642},
      note={cited By 105},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84975144038&doi=10.1021%2facsami.6b03642&partnerID=40&md5=158f699cb4e916087d4cd33e1e54d675},
      affiliation={Leibniz Institute for Solid State and Materials Research (IFW) Dresden E.V., Dresden, D-01171, Germany; Institut für Werkstoffwissenschaft, Technische Universität Dresden, Helmholtzstraße 7, Dresden, D-01069, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Helmholtzstraße 7, Dresden, D-01069, Germany; Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Department of Materials Physics, Montanuniversität Leoben, Jahnstrasse 12, Leoben, A-8700, Austria},
      abstract={Because of the outstanding high theoretical specific energy density of 2600 Wh kg-1, the lithium-sulfur (Li-S) battery is regarded as a promising candidate for post lithium-ion battery systems eligible to meet the forthcoming market requirements. However, its commercialization on large scale is thwarted by fast capacity fading caused by the Achilles' heel of Li-S systems: the polysulfide shuttle. Here, we merge the physical features of carbon-coated separators and the unique chemical properties of N and S codoped mesoporous carbon to create a functional hybrid separator with superior polysulfide affinity and electrochemical benefits. DFT calculations revealed that carbon materials with N and S codoping possess a strong binding energy to high-order polysulfide species, which is essential to keep the active material in the cathode side. As a result of the synergistic effect of N, S dual-doping, an advanced Li-S cell with high specific capacity and ultralow capacity degradation of 0.041% per cycle is achieved. Pushing our simple-designed and scalable cathode to a highly increased sulfur loading of 5.4 mg cm-2, the Li-S cell with the functional hybrid separator can deliver a remarkable areal capacity of 5.9 mAh cm-2, which is highly favorable for practical applications. © 2016 American Chemical Society.},
      author_keywords={DFT calculation; hybrid separator; lithium-sulfur battery; mesoporous carbon coating; nitrogen/sulfur codoped; polysulfide adsorption},
      document_type={Article},
      source={Scopus},
      }

  • ReaxFF+-A New Reactive Force Field Method for the Accurate Description of Ionic Systems and Its Application to the Hydrolyzation of Aluminosilicates
    • O. Böhm, S. Pfadenhauer, R. Leitsmann, P. Plänitz, E. Schreiner, M. Schreiber
    • Journal of Physical Chemistry C 120, 10849-10856 (2016)
    • DOI   Abstract  

      In this paper we present a powerful extension of the reactive force field method ReaxFF, which we call ReaxFF+. It combines the charge equilibrium scheme with the bond order principle. The main advantage of this procedure is the correct distinction and description of covalent and ionic bonds. It allows reactive molecular dynamic simulations in ionic gases and liquids. To demonstrate the accuracy of this new method, we study the hydrolyzation of aluminosilicates. Comparing the results with experimental and ab initio data, we can prove the high accuracy of our method. This shows that ReaxFF+ is a powerful force field simulation tool for reactions in acidic or alkaline environments. © 2016 American Chemical Society.

      @ARTICLE{Böhm201610849,
      author={Böhm, O. and Pfadenhauer, S. and Leitsmann, R. and Plänitz, P. and Schreiner, E. and Schreiber, M.},
      title={ReaxFF+-A New Reactive Force Field Method for the Accurate Description of Ionic Systems and Its Application to the Hydrolyzation of Aluminosilicates},
      journal={Journal of Physical Chemistry C},
      year={2016},
      volume={120},
      number={20},
      pages={10849-10856},
      doi={10.1021/acs.jpcc.6b00720},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971406203&doi=10.1021%2facs.jpcc.6b00720&partnerID=40&md5=184334bdb0e680d7f3b5bdd5fa101229},
      affiliation={AQcomputare Gesellschaft für Materialberechnung MbH, Annabergerstrasse 240, Chemnitz, 09125, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01069, Germany; BASF SE, GMC/MM-B001, Ludwigshafen, 67056, Germany; Institut für Physik, Technische Universität Chemnitz, Chemnitz, 09107, Germany},
      abstract={In this paper we present a powerful extension of the reactive force field method ReaxFF, which we call ReaxFF+. It combines the charge equilibrium scheme with the bond order principle. The main advantage of this procedure is the correct distinction and description of covalent and ionic bonds. It allows reactive molecular dynamic simulations in ionic gases and liquids. To demonstrate the accuracy of this new method, we study the hydrolyzation of aluminosilicates. Comparing the results with experimental and ab initio data, we can prove the high accuracy of our method. This shows that ReaxFF+ is a powerful force field simulation tool for reactions in acidic or alkaline environments. © 2016 American Chemical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Towards an optimal contact metal for CNTFETs
    • A. Fediai, D. A. Ryndyk, G. Seifert, S. Mothes, M. Claus, M. Schröter, G. Cuniberti
    • Nanoscale 8, 10240-10251 (2016)
    • DOI   Abstract  

      Downscaling of the contact length Lc of a side-contacted carbon nanotube field-effect transistor (CNTFET) is challenging because of the rapidly increasing contact resistance as Lc falls below 20-50 nm. If in agreement with existing experimental results, theoretical work might answer the question, which metals yield the lowest CNT-metal contact resistance and what physical mechanisms govern the geometry dependence of the contact resistance. However, at the scale of 10 nm, parameter-free models of electron transport become computationally prohibitively expensive. In our work we used a dedicated combination of the Green function formalism and density functional theory to perform an overall ab initio simulation of extended CNT-metal contacts of an arbitrary length (including infinite), a previously not achievable level of simulations. We provide a systematic and comprehensive discussion of metal-CNT contact properties as a function of the metal type and the contact length. We have found and been able to explain very uncommon relations between chemical, physical and electrical properties observed in CNT-metal contacts. The calculated electrical characteristics are in reasonable quantitative agreement and exhibit similar trends as the latest experimental data in terms of: (i) contact resistance for Lc = ∞, (ii) scaling of contact resistance Rc(Lc); (iii) metal-defined polarity of a CNTFET. Our results can guide technology development and contact material selection for downscaling the length of side-contacts below 10 nm. © 2016 The Royal Society of Chemistry.

      @ARTICLE{Fediai201610240,
      author={Fediai, A. and Ryndyk, D.A. and Seifert, G. and Mothes, S. and Claus, M. and Schröter, M. and Cuniberti, G.},
      title={Towards an optimal contact metal for CNTFETs},
      journal={Nanoscale},
      year={2016},
      volume={8},
      number={19},
      pages={10240-10251},
      doi={10.1039/c6nr01012a},
      note={cited By 29},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971246371&doi=10.1039%2fc6nr01012a&partnerID=40&md5=8782b1e4245616c7fce303d0c04947a5},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Theoretical Chemistry, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Department for Electron Devices and Integrated Circuits, TU Dresden, Dresden, 01062, Germany},
      abstract={Downscaling of the contact length Lc of a side-contacted carbon nanotube field-effect transistor (CNTFET) is challenging because of the rapidly increasing contact resistance as Lc falls below 20-50 nm. If in agreement with existing experimental results, theoretical work might answer the question, which metals yield the lowest CNT-metal contact resistance and what physical mechanisms govern the geometry dependence of the contact resistance. However, at the scale of 10 nm, parameter-free models of electron transport become computationally prohibitively expensive. In our work we used a dedicated combination of the Green function formalism and density functional theory to perform an overall ab initio simulation of extended CNT-metal contacts of an arbitrary length (including infinite), a previously not achievable level of simulations. We provide a systematic and comprehensive discussion of metal-CNT contact properties as a function of the metal type and the contact length. We have found and been able to explain very uncommon relations between chemical, physical and electrical properties observed in CNT-metal contacts. The calculated electrical characteristics are in reasonable quantitative agreement and exhibit similar trends as the latest experimental data in terms of: (i) contact resistance for Lc = ∞, (ii) scaling of contact resistance Rc(Lc); (iii) metal-defined polarity of a CNTFET. Our results can guide technology development and contact material selection for downscaling the length of side-contacts below 10 nm. © 2016 The Royal Society of Chemistry.},
      document_type={Article},
      source={Scopus},
      }

  • Continuum modelling of semiconductor heteroepitaxy: an applied perspective
    • R. Bergamaschini, M. Salvalaglio, R. Backofen, A. Voigt, F. Montalenti
    • Advances in Physics: X 1, 331-367 (2016)
    • DOI   Abstract  

      Semiconductor heteroepitaxy involves a wealth of qualitatively different, competing phenomena. Examples include three-dimensional island formation, injection of dislocations, mixing between film and substrate atoms. Their relative importance depends on the specific growth conditions, giving rise to a very complex scenario. The need for an optimal control over heteroepitaxial films and/or nanostructures is widespread: semiconductor epitaxy by molecular beam epitaxy or chemical vapour deposition is nowadays exploited also in industrial environments. Simulation models can be precious in limiting the parameter space to be sampled while aiming at films/nanostructures with the desired properties. In order to be appealing (and useful) to an applied audience, such models must yield predictions directly comparable with experimental data. This implies matching typical time scales and sizes, while offering a satisfactory description of the main physical driving forces. It is the aim of the present review to show that continuum models of semiconductor heteroepitaxy evolved significantly, providing a promising tool (even a working tool, in some cases) to comply with the above requirements. Several examples, spanning from the nanometre to the micron scale, are illustrated. Current limitations and future research directions are also discussed. © 2016, © 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

      @ARTICLE{Bergamaschini2016331,
      author={Bergamaschini, R. and Salvalaglio, M. and Backofen, R. and Voigt, A. and Montalenti, F.},
      title={Continuum modelling of semiconductor heteroepitaxy: an applied perspective},
      journal={Advances in Physics: X},
      year={2016},
      volume={1},
      number={3},
      pages={331-367},
      doi={10.1080/23746149.2016.1181986},
      note={cited By 21},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84995674502&doi=10.1080%2f23746149.2016.1181986&partnerID=40&md5=23d7c05aa51a532635f7af363d139e9f},
      affiliation={L-NESS and Department of Materials Science, Università degli Studi di Milano-Bicocca, Milano, Italy; Institut für Wissenschaftliches Rechnen, Technische Universität Dresden, Dresden, Germany; Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, Dresden, Germany},
      abstract={Semiconductor heteroepitaxy involves a wealth of qualitatively different, competing phenomena. Examples include three-dimensional island formation, injection of dislocations, mixing between film and substrate atoms. Their relative importance depends on the specific growth conditions, giving rise to a very complex scenario. The need for an optimal control over heteroepitaxial films and/or nanostructures is widespread: semiconductor epitaxy by molecular beam epitaxy or chemical vapour deposition is nowadays exploited also in industrial environments. Simulation models can be precious in limiting the parameter space to be sampled while aiming at films/nanostructures with the desired properties. In order to be appealing (and useful) to an applied audience, such models must yield predictions directly comparable with experimental data. This implies matching typical time scales and sizes, while offering a satisfactory description of the main physical driving forces. It is the aim of the present review to show that continuum models of semiconductor heteroepitaxy evolved significantly, providing a promising tool (even a working tool, in some cases) to comply with the above requirements. Several examples, spanning from the nanometre to the micron scale, are illustrated. Current limitations and future research directions are also discussed. © 2016, © 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.},
      author_keywords={02.70.-c Computational techniques; 68.55.-a Thin-film structure and morphology; 68.55.ag Semiconductors; 81.15.Aa Theory and models of film growth; continuum modelling; dislocations; Heteroepitaxy; intermixing; phase-field; simulations},
      document_type={Review},
      source={Scopus},
      }

  • Analyses of interaction mechanisms during forming of multilayer carbon woven fabrics for composite applications
    • F. Nosrat Nezami, T. Gereke, C. Cherif
    • Composites Part A: Applied Science and Manufacturing 84, 406-416 (2016)
    • DOI   Abstract  

      The use of textile reinforcing structures provides enormous possibilities in the design of lightweight composites. However, the physical mechanisms during fabric forming are complex and far from being fully understood especially in multilayer draping. The aims of this study are the analyses of interaction mechanisms of individual textile layers during the forming operation and of defects arising from interactions. In basic experiments of the carbon woven fabric, friction properties and the fabric integrity were investigated. In single and multilayer draping experiments the findings were transferred to the composite preforming process. Interaction defects are characterised as interdependency between the acting inter-ply shear forces and the structural integrity of the fabric. The defects resulting from the interactions depend on the configuration of the fabric (e. g. shearing) and the acting normal forces. The reduction of friction is crucial for the preform quality but is opposite to an actively force-controlled material manipulation. © 2016 Elsevier Ltd. All rights reserved.

      @ARTICLE{NosratNezami2016406,
      author={Nosrat Nezami, F. and Gereke, T. and Cherif, C.},
      title={Analyses of interaction mechanisms during forming of multilayer carbon woven fabrics for composite applications},
      journal={Composites Part A: Applied Science and Manufacturing},
      year={2016},
      volume={84},
      pages={406-416},
      doi={10.1016/j.compositesa.2016.02.023},
      note={cited By 40},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959512140&doi=10.1016%2fj.compositesa.2016.02.023&partnerID=40&md5=5c5b84172beee41a9dd039f3ec1024a1},
      affiliation={CIKONI Composites Innovation, Stuttgart, 70569, Germany; Technische Universität Dresden, Institute of Textile Machinery, High Performance Material Technology (ITM), Dresden, 01062, Germany; Technische Universität Dresden, Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany},
      abstract={The use of textile reinforcing structures provides enormous possibilities in the design of lightweight composites. However, the physical mechanisms during fabric forming are complex and far from being fully understood especially in multilayer draping. The aims of this study are the analyses of interaction mechanisms of individual textile layers during the forming operation and of defects arising from interactions. In basic experiments of the carbon woven fabric, friction properties and the fabric integrity were investigated. In single and multilayer draping experiments the findings were transferred to the composite preforming process. Interaction defects are characterised as interdependency between the acting inter-ply shear forces and the structural integrity of the fabric. The defects resulting from the interactions depend on the configuration of the fabric (e. g. shearing) and the acting normal forces. The reduction of friction is crucial for the preform quality but is opposite to an actively force-controlled material manipulation. © 2016 Elsevier Ltd. All rights reserved.},
      author_keywords={A. Carbon fiber; A. Fabrics/textiles; E. Forming; Friction},
      document_type={Article},
      source={Scopus},
      }

  • Relaxed incremental variational approach for the modeling of damage-induced stress hysteresis in arterial walls
    • T. Schmidt, D. Balzani
    • Journal of the Mechanical Behavior of Biomedical Materials 58, 149-162 (2016)
    • DOI   Abstract  

      In this paper, a three-dimensional relaxed incremental variational damage model is proposed, which enables the description of complex softening hysteresis as observed in supra-physiologically loaded arterial tissues, and which thereby avoids a loss of convexity of the underlying formulation. The proposed model extends the relaxed formulation of Balzani and Ortiz [2012. Relaxed incremental variational formulation for damage at large strains with application to fiber-reinforced materials and materials with truss-like microstructures. Int. J. Numer. Methods Eng. 92, 551-570], such that the typical stress-hysteresis observed in arterial tissues under cyclic loading can be described. This is mainly achieved by constructing a modified one-dimensional model accounting for cyclic loading in the individual fiber direction and numerically homogenizing the response taking into account a fiber orientation distribution function. A new solution strategy for the identification of the convexified stress potential is proposed based on an evolutionary algorithm which leads to an improved robustness compared to solely Newton-based optimization schemes. In order to enable an efficient adjustment of the new model to experimentally observed softening hysteresis, an adjustment scheme using a surrogate model is proposed. Therewith, the relaxed formulation is adjusted to experimental data in the supra-physiological domain of the media and adventitia of a human carotid artery. The performance of the model is then demonstrated in a finite element example of an overstretched artery. Although here three-dimensional thick-walled atherosclerotic arteries are considered, it is emphasized that the formulation can also directly be applied to thin-walled simulations of arteries using shell elements or other fiber-reinforced biomembranes. © 2015 Elsevier Ltd.

      @ARTICLE{Schmidt2016149,
      author={Schmidt, T. and Balzani, D.},
      title={Relaxed incremental variational approach for the modeling of damage-induced stress hysteresis in arterial walls},
      journal={Journal of the Mechanical Behavior of Biomedical Materials},
      year={2016},
      volume={58},
      pages={149-162},
      doi={10.1016/j.jmbbm.2015.08.005},
      note={cited By 5},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940759317&doi=10.1016%2fj.jmbbm.2015.08.005&partnerID=40&md5=c10b35ead3ebbabc944208d1cee1ca6c},
      affiliation={Institut für Mechanik, Fakultät für Ingenieurwissenschaften/Abteilung Bauwissenschaften, Universität Duisburg-Essen, Universitätsstr. 15, Essen, 45141, Germany; Institut für Mechanik und Flächentragwerke, Fakultät Bauingenieurwesen, Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, 01062, Germany},
      abstract={In this paper, a three-dimensional relaxed incremental variational damage model is proposed, which enables the description of complex softening hysteresis as observed in supra-physiologically loaded arterial tissues, and which thereby avoids a loss of convexity of the underlying formulation. The proposed model extends the relaxed formulation of Balzani and Ortiz [2012. Relaxed incremental variational formulation for damage at large strains with application to fiber-reinforced materials and materials with truss-like microstructures. Int. J. Numer. Methods Eng. 92, 551-570], such that the typical stress-hysteresis observed in arterial tissues under cyclic loading can be described. This is mainly achieved by constructing a modified one-dimensional model accounting for cyclic loading in the individual fiber direction and numerically homogenizing the response taking into account a fiber orientation distribution function. A new solution strategy for the identification of the convexified stress potential is proposed based on an evolutionary algorithm which leads to an improved robustness compared to solely Newton-based optimization schemes. In order to enable an efficient adjustment of the new model to experimentally observed softening hysteresis, an adjustment scheme using a surrogate model is proposed. Therewith, the relaxed formulation is adjusted to experimental data in the supra-physiological domain of the media and adventitia of a human carotid artery. The performance of the model is then demonstrated in a finite element example of an overstretched artery. Although here three-dimensional thick-walled atherosclerotic arteries are considered, it is emphasized that the formulation can also directly be applied to thin-walled simulations of arteries using shell elements or other fiber-reinforced biomembranes. © 2015 Elsevier Ltd.},
      author_keywords={Atherosclerotic arteries; Convexity; Mesh-independency; Orientation distribution; Soft biological tissues; Softening},
      document_type={Article},
      source={Scopus},
      }

  • Electronic Structure of the Dark Surface of the Weak Topological Insulator Bi14Rh3I9
    • C. Pauly, B. Rasche, K. Koepernik, M. Richter, S. Borisenko, M. Liebmann, M. Ruck, J. Van Den Brink, M. Morgenstern
    • ACS Nano 10, 3995-4003 (2016)
    • DOI   Abstract  

      Compound Bi14Rh3I9 consists of ionic stacks of intermetallic [(Bi4Rh)3I]2+ and insulating [Bi2I8]2- layers and has been identified to be a weak topological insulator. Scanning tunneling microscopy revealed the robust edge states at all step edges of the cationic layer as a topological fingerprint. However, these edge states are found 0.25 eV below the Fermi level, which is an obstacle for transport experiments. Here, we address this obstacle by comparing results of density functional slab calculations with scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy. We show that the n-type doping of the intermetallic layer is intrinsically caused by the polar surface and is well-screened toward the bulk. In contrast, the anionic spacer layer shows a gap at the Fermi level, both on the surface and in the bulk; that is, it is not surface-doped due to iodine desorption. The well-screened surface dipole implies that a buried edge state, probably already below a single spacer layer, is located at the Fermi level. Consequently, a multilayer step covered by a spacer layer could provide access to the transport properties of the topological edge states. In addition, we find a lateral electronic modulation of the topologically nontrivial surface layer, which is traced back to the coupling with the underlying zigzag chain structure of the spacer layer. © 2016 American Chemical Society.

      @ARTICLE{Pauly20163995,
      author={Pauly, C. and Rasche, B. and Koepernik, K. and Richter, M. and Borisenko, S. and Liebmann, M. and Ruck, M. and Van Den Brink, J. and Morgenstern, M.},
      title={Electronic Structure of the Dark Surface of the Weak Topological Insulator Bi14Rh3I9},
      journal={ACS Nano},
      year={2016},
      volume={10},
      number={4},
      pages={3995-4003},
      doi={10.1021/acsnano.6b00841},
      note={cited By 16},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84966783716&doi=10.1021%2facsnano.6b00841&partnerID=40&md5=b6618aaab2b015aea03fae8b96c1fe58},
      affiliation={II. Institute of Physics B and JARA-FIT, RWTH Aachen University, Aachen, D-52074, Germany; Department of Chemistry and Food Chemistry, TU Dresden, Dresden, D-01062, Germany; Leibniz Institute for Solid State and Materials Research, IFW Dresden E.V., P.O. Box 270116, Dresden, D-01171, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, D-01069, Germany; Max Planck Institute for Chemical Physics of Solids, Dresden, D-01187, Germany},
      abstract={Compound Bi14Rh3I9 consists of ionic stacks of intermetallic [(Bi4Rh)3I]2+ and insulating [Bi2I8]2- layers and has been identified to be a weak topological insulator. Scanning tunneling microscopy revealed the robust edge states at all step edges of the cationic layer as a topological fingerprint. However, these edge states are found 0.25 eV below the Fermi level, which is an obstacle for transport experiments. Here, we address this obstacle by comparing results of density functional slab calculations with scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy. We show that the n-type doping of the intermetallic layer is intrinsically caused by the polar surface and is well-screened toward the bulk. In contrast, the anionic spacer layer shows a gap at the Fermi level, both on the surface and in the bulk; that is, it is not surface-doped due to iodine desorption. The well-screened surface dipole implies that a buried edge state, probably already below a single spacer layer, is located at the Fermi level. Consequently, a multilayer step covered by a spacer layer could provide access to the transport properties of the topological edge states. In addition, we find a lateral electronic modulation of the topologically nontrivial surface layer, which is traced back to the coupling with the underlying zigzag chain structure of the spacer layer. © 2016 American Chemical Society.},
      author_keywords={density functional theory calculation; scanning tunneling spectroscopy; topological insulators},
      document_type={Article},
      source={Scopus},
      }

  • Tetracene Formation by On-Surface Reduction
    • J. Krüger, N. Pavliček, J. M. Alonso, D. Pérez, E. Guitián, T. Lehmann, G. Cuniberti, A. Gourdon, G. Meyer, L. Gross, F. Moresco, D. Peña
    • ACS Nano 10, 4538-4542 (2016)
    • DOI   Abstract  

      We present the on-surface reduction of diepoxytetracenes to form genuine tetracene on Cu(111). The conversion is achieved by scanning tunneling microscopy (STM) tip-induced manipulation as well as thermal activation and is conclusively demonstrated by means of atomic force microscopy (AFM) with atomic resolution. We observe that the metallic surface plays an important role in the deoxygenation and for the planarization after bond cleavage. © 2016 American Chemical Society.

      @ARTICLE{Krüger20164538,
      author={Krüger, J. and Pavliček, N. and Alonso, J.M. and Pérez, D. and Guitián, E. and Lehmann, T. and Cuniberti, G. and Gourdon, A. and Meyer, G. and Gross, L. and Moresco, F. and Peña, D.},
      title={Tetracene Formation by On-Surface Reduction},
      journal={ACS Nano},
      year={2016},
      volume={10},
      number={4},
      pages={4538-4542},
      doi={10.1021/acsnano.6b00505},
      note={cited By 40},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84967327868&doi=10.1021%2facsnano.6b00505&partnerID=40&md5=159ee732cc1844bba093d59c3f453f1a},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01069, Germany; IBM Research-Zurich, Rüschlikon, 8803, Switzerland; Centro de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Departamento de Química Orgánica, Universidade de Santiago de Compostela, Santiago de Compostela, 15782, Spain; Centre DÉlaboration de Matériaux et DÉtudes Structurales (CEMES), UPR 8011 CNRS, Nanosciences Group, 29 Rue Jeanne Marvig, Toulouse, 31055, France; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01069, Germany},
      abstract={We present the on-surface reduction of diepoxytetracenes to form genuine tetracene on Cu(111). The conversion is achieved by scanning tunneling microscopy (STM) tip-induced manipulation as well as thermal activation and is conclusively demonstrated by means of atomic force microscopy (AFM) with atomic resolution. We observe that the metallic surface plays an important role in the deoxygenation and for the planarization after bond cleavage. © 2016 American Chemical Society.},
      author_keywords={acenes; atomic force microscopy (AFM); deoxygenation; on-surface reaction; single-molecule chemistry},
      document_type={Article},
      source={Scopus},
      }

  • Influence of organic ligands on the line shape of the Kondo resonance
    • J. Meyer, R. Ohmann, A. Nickel, C. Toher, R. Gresser, K. Leo, D. A. Ryndyk, F. Moresco, G. Cuniberti
    • Physical Review B 93, 155118 (2016)
    • DOI   Abstract  

      The Kondo resonance of an organic molecule containing a Co atom is investigated by scanning tunneling spectroscopy and ab initio calculations on a Ag(100) surface. High resolution mapping of the line shape shows evidence of local nonradially symmetric variations of the Fano factor and the Kondo amplitude, revealing a strong influence of the molecular ligand. We show that the decay of the amplitude of the Kondo resonance is determined by the spatial distribution of the ligand's orbital being hybridized with the singly occupied Co dz2 orbital, forming together the singly occupied Kondo-active orbital. © 2016 American Physical Society.

      @ARTICLE{Meyer2016,
      author={Meyer, J. and Ohmann, R. and Nickel, A. and Toher, C. and Gresser, R. and Leo, K. and Ryndyk, D.A. and Moresco, F. and Cuniberti, G.},
      title={Influence of organic ligands on the line shape of the Kondo resonance},
      journal={Physical Review B},
      year={2016},
      volume={93},
      number={15},
      doi={10.1103/PhysRevB.93.155118},
      art_number={155118},
      note={cited By 6},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963717509&doi=10.1103%2fPhysRevB.93.155118&partnerID=40&md5=633e441d9ebbf5effb57ac73c4d03e87},
      affiliation={Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden, TU Dresden, Dresden, 01062, Germany; Institut für Angewandte Photophysik (IAPP), Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), TU Dresden, Dresden, 01062, Germany; Energy Materials and Surface Sciences Unit (EMSS), Okinawa Institute of Science and Technology, Graduate University (OIST), 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan; Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708, United States},
      abstract={The Kondo resonance of an organic molecule containing a Co atom is investigated by scanning tunneling spectroscopy and ab initio calculations on a Ag(100) surface. High resolution mapping of the line shape shows evidence of local nonradially symmetric variations of the Fano factor and the Kondo amplitude, revealing a strong influence of the molecular ligand. We show that the decay of the amplitude of the Kondo resonance is determined by the spatial distribution of the ligand's orbital being hybridized with the singly occupied Co dz2 orbital, forming together the singly occupied Kondo-active orbital. © 2016 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • Friction and adhesion mediated by supramolecular host-guest complexes
    • R. Guerra, A. Benassi, A. Vanossi, M. Ma, M. Urbakh
    • Physical Chemistry Chemical Physics 18, 9248-9254 (2016)
    • DOI   Abstract  

      The adhesive and frictional response of an AFM tip connected to a substrate through supramolecular host-guest complexes is investigated by dynamic Monte Carlo simulations. Here, the variation of the pull-off force with the unloading rate recently observed in experiments is unraveled by evidencing simultaneous (progressive) breaking of the bonds at fast (slow) rates. The model reveals the origin of the observed plateaus in the retraction force as a function of the tip-surface distance, showing that they result from the tip geometrical features. In lateral sliding, the model exhibits a wide range of dynamic behaviors ranging from smooth sliding to stick-slip at different velocities, with the average friction force determined by the characteristic formation/rupture rates of the complexes. In particular, it is shown that for some molecular complexes friction can become almost constant over a wide range of velocities. Also, we show the possibility of exploiting the ageing effect through slide-hold-slide experiments, in order to infer the characteristic formation rate. Finally, our model predicts a novel "anti-ageing" effect which is characterized by a decrease of the static friction force with the hold time. Such an effect is explained in terms of enhancement of adhesion during sliding, especially observed at high driving velocities. © the Owner Societies 2016.

      @ARTICLE{Guerra20169248,
      author={Guerra, R. and Benassi, A. and Vanossi, A. and Ma, M. and Urbakh, M.},
      title={Friction and adhesion mediated by supramolecular host-guest complexes},
      journal={Physical Chemistry Chemical Physics},
      year={2016},
      volume={18},
      number={13},
      pages={9248-9254},
      doi={10.1039/c6cp00661b},
      note={cited By 8},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962027565&doi=10.1039%2fc6cp00661b&partnerID=40&md5=1b0b9d96f2217468276d325d058fb761},
      affiliation={International School for Advanced Studies (SISSA), Via Bonomea 265, Trieste, 34136, Italy; CNR, IOM, Democritos National Simulation Center, Via Bonomea 265, Trieste, 34136, Italy; Institute for Materials Science, Max Bergmann Center of Biomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCCMS), TU Dresden, Dresden, 01062, Germany; School of Chemistry, Tel Aviv University, Tel Aviv, 69978, Israel; Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv, 6997801, Israel},
      abstract={The adhesive and frictional response of an AFM tip connected to a substrate through supramolecular host-guest complexes is investigated by dynamic Monte Carlo simulations. Here, the variation of the pull-off force with the unloading rate recently observed in experiments is unraveled by evidencing simultaneous (progressive) breaking of the bonds at fast (slow) rates. The model reveals the origin of the observed plateaus in the retraction force as a function of the tip-surface distance, showing that they result from the tip geometrical features. In lateral sliding, the model exhibits a wide range of dynamic behaviors ranging from smooth sliding to stick-slip at different velocities, with the average friction force determined by the characteristic formation/rupture rates of the complexes. In particular, it is shown that for some molecular complexes friction can become almost constant over a wide range of velocities. Also, we show the possibility of exploiting the ageing effect through slide-hold-slide experiments, in order to infer the characteristic formation rate. Finally, our model predicts a novel "anti-ageing" effect which is characterized by a decrease of the static friction force with the hold time. Such an effect is explained in terms of enhancement of adhesion during sliding, especially observed at high driving velocities. © the Owner Societies 2016.},
      document_type={Article},
      source={Scopus},
      }

  • Stress Induced Branching of Growing Crystals on Curved Surfaces
    • C. Köhler, R. Backofen, A. Voigt
    • Physical Review Letters 116, 135502 (2016)
    • DOI   Abstract  

      If two-dimensional crystals grow on a curved surface, the Gaussian curvature of the surface induces elastic stress and affects the growth pathway. The elastic stress can be alleviated by incorporating defects or, if this is energetically unfavorable, via an elastic instability which leads to anisotropic growth with branched ribbonlike structures. This instability provides a generic route to grow defect-free crystals on curved surfaces. Depending on the elastic properties of the crystal and the geometric properties of the surface, different growth morphologies with two-, four-, and sixfold symmetry develop. Using a phase field crystal type modeling approach, we provide a microscopic understanding of the morphology selection. © 2016 American Physical Society.

      @ARTICLE{Köhler2016,
      author={Köhler, C. and Backofen, R. and Voigt, A.},
      title={Stress Induced Branching of Growing Crystals on Curved Surfaces},
      journal={Physical Review Letters},
      year={2016},
      volume={116},
      number={13},
      doi={10.1103/PhysRevLett.116.135502},
      art_number={135502},
      note={cited By 17},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963647565&doi=10.1103%2fPhysRevLett.116.135502&partnerID=40&md5=b0d3ce9633ac0948a2de0a6bcf800bcb},
      affiliation={Institute of Scientific Computing, Technische Universität Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCMS), Dresden, 01062, Germany},
      abstract={If two-dimensional crystals grow on a curved surface, the Gaussian curvature of the surface induces elastic stress and affects the growth pathway. The elastic stress can be alleviated by incorporating defects or, if this is energetically unfavorable, via an elastic instability which leads to anisotropic growth with branched ribbonlike structures. This instability provides a generic route to grow defect-free crystals on curved surfaces. Depending on the elastic properties of the crystal and the geometric properties of the surface, different growth morphologies with two-, four-, and sixfold symmetry develop. Using a phase field crystal type modeling approach, we provide a microscopic understanding of the morphology selection. © 2016 American Physical Society.},
      document_type={Article},
      source={Scopus},
      }

  • An efficient coarse-grained approach for the electron transport through large molecular systems under dephasing environment
    • D. Nozaki, R. Bustos-Marún, C. J. Cattena, G. Cuniberti, H. M. Pastawski
    • European Physical Journal B 89, 102 (2016)
    • DOI   Abstract  

      Dephasing effects in electron transport in molecular systems connected between contacts average out the quantum characteristics of the system, forming a bridge to the classical behavior as the size of the system increases. For the evaluation of the conductance of the molecular systems which have sizes within this boundary domain, it is necessary to include these dephasing effects. These effects can be calculated by using the D’Amato-Pastawski model. However, this method is computationally demanding for large molecular systems since transmission functions for all pairs of atomic orbitals need to be calculated. To overcome this difficulty, we develop an efficient coarse-grained model for the calculation of conductance of molecular junctions including decoherence. By analyzing the relationship between chemical potential and inter-molecular coupling, we find that the chemical potential drops stepwise in the systems with weaker inter-unit coupling. Using this property, an efficient coarse-grained algorithm which can reduce computational costs considerably without losing the accuracy is derived and applied to one-dimensional organic systems as a demonstration. This model can be used for the study of the orientation dependence of conductivity in various phases (amorphous, crystals, and polymers) of large molecular systems such as organic semiconducting materials. © 2016, EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

      @ARTICLE{Nozaki2016,
      author={Nozaki, D. and Bustos-Marún, R. and Cattena, C.J. and Cuniberti, G. and Pastawski, H.M.},
      title={An efficient coarse-grained approach for the electron transport through large molecular systems under dephasing environment},
      journal={European Physical Journal B},
      year={2016},
      volume={89},
      number={4},
      doi={10.1140/epjb/e2016-70013-y},
      art_number={102},
      note={cited By 3},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963831269&doi=10.1140%2fepjb%2fe2016-70013-y&partnerID=40&md5=2fed4340a75906733d757f5e08fdd1ce},
      affiliation={Institute for Materials Science and Max Bergmann Center ofBiomaterials, TU Dresden, Dresden, 01062, Germany; Dresden Center for Computational Materials Science (DCCMS), TUDresden, Dresden, 01062, Germany; Center for Advancing Electronics Dresden (cfAED), TUDresden, Dresden, 01062, Germany; Lehrstuhl für Theoretische Physik, UniversitätPaderborn, Paderborn, Germany; Instituto de Física Enrique Gaviola and Facultad de MatemáticaAstronomía y Física, Universidad Nacional de Córdoba, CiudadUniversitaria, Córdoba, 5000, Argentina; Faculdad de Ciencias Químicas, Universidad Nacional de Córdoba,Ciudad Universitaria, Córdoba, 5000, Argentina},
      abstract={Dephasing effects in electron transport in molecular systems connected between contacts average out the quantum characteristics of the system, forming a bridge to the classical behavior as the size of the system increases. For the evaluation of the conductance of the molecular systems which have sizes within this boundary domain, it is necessary to include these dephasing effects. These effects can be calculated by using the D’Amato-Pastawski model. However, this method is computationally demanding for large molecular systems since transmission functions for all pairs of atomic orbitals need to be calculated. To overcome this difficulty, we develop an efficient coarse-grained model for the calculation of conductance of molecular junctions including decoherence. By analyzing the relationship between chemical potential and inter-molecular coupling, we find that the chemical potential drops stepwise in the systems with weaker inter-unit coupling. Using this property, an efficient coarse-grained algorithm which can reduce computational costs considerably without losing the accuracy is derived and applied to one-dimensional organic systems as a demonstration. This model can be used for the study of the orientation dependence of conductivity in various phases (amorphous, crystals, and polymers) of large molecular systems such as organic semiconducting materials. © 2016, EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.},
      author_keywords={Mesoscopic and Nanoscale Systems},
      document_type={Article},
      source={Scopus},
      }

  • Reproducibility in density functional theory calculations of solids
    • K. Lejaeghere, G. Bihlmayer, T. Björkman, P. Blaha, S. Blügel, V. Blum, D. Caliste, I. E. Castelli, S. J. Clark, A. Dal Corso, S. De Gironcoli, T. Deutsch, J. K. Dewhurst, I. Di Marco, C. Draxl, M. Dułak, O. Eriksson, J. A. Flores-Livas, K. F. Garrity, L. Genovese, P. Giannozzi, M. Giantomassi, S. Goedecker, X. Gonze, O. Grånäs, E. K. U. Gross, A. Gulans, F. Gygi, D. R. Hamann, P. J. Hasnip, N. A. W. Holzwarth, D. Iuşan, D. B. Jochym, F. Jollet, D. Jones, G. Kresse, K. Koepernik, E. Küçükbenli, Y. O. Kvashnin, I. L. M. Locht, S. Lubeck, M. Marsman, N. Marzari, U. Nitzsche, L. Nordström, T. Ozaki, L. Paulatto, C. J. Pickard, W. Poelmans, M. I. J. Probert, K. Refson, M. Richter, G. -M. Rignanese, S. Saha, M. Scheffler, M. Schlipf, K. Schwarz, S. Sharma, F. Tavazza, P. Thunström, A. Tkatchenko, M. Torrent, D. Vanderbilt, M. J. Van Setten, V. Van Speybroeck, J. M. Wills, J. R. Yates, G. -X. Zhang, S. Cottenier
    • Science 351, aad3000 (2016)
    • DOI   Abstract  

      The widespread popularity of density functional theory has given rise to an extensive range of dedicated codes for predicting molecular and crystalline properties. However, each code implements the formalism in a different way, raising questions about the reproducibility of such predictions.We report the results of a community-wide effort that compared 15 solid-state codes, using 40 different potentials or basis set types, to assess the quality of the Perdew-Burke-Ernzerhof equations of state for 71 elemental crystals. We conclude that predictions from recent codes and pseudopotentials agree very well, with pairwise differences that are comparable to those between different high-precision experiments. Older methods, however, have less precise agreement. Our benchmark provides a framework for users and developers to document the precision of new applications and methodological improvements.

      @ARTICLE{Lejaeghere2016,
      author={Lejaeghere, K. and Bihlmayer, G. and Björkman, T. and Blaha, P. and Blügel, S. and Blum, V. and Caliste, D. and Castelli, I.E. and Clark, S.J. and Dal Corso, A. and De Gironcoli, S. and Deutsch, T. and Dewhurst, J.K. and Di Marco, I. and Draxl, C. and Dułak, M. and Eriksson, O. and Flores-Livas, J.A. and Garrity, K.F. and Genovese, L. and Giannozzi, P. and Giantomassi, M. and Goedecker, S. and Gonze, X. and Grånäs, O. and Gross, E.K.U. and Gulans, A. and Gygi, F. and Hamann, D.R. and Hasnip, P.J. and Holzwarth, N.A.W. and Iuşan, D. and Jochym, D.B. and Jollet, F. and Jones, D. and Kresse, G. and Koepernik, K. and Küçükbenli, E. and Kvashnin, Y.O. and Locht, I.L.M. and Lubeck, S. and Marsman, M. and Marzari, N. and Nitzsche, U. and Nordström, L. and Ozaki, T. and Paulatto, L. and Pickard, C.J. and Poelmans, W. and Probert, M.I.J. and Refson, K. and Richter, M. and Rignanese, G.-M. and Saha, S. and Scheffler, M. and Schlipf, M. and Schwarz, K. and Sharma, S. and Tavazza, F. and Thunström, P. and Tkatchenko, A. and Torrent, M. and Vanderbilt, D. and Van Setten, M.J. and Van Speybroeck, V. and Wills, J.M. and Yates, J.R. and Zhang, G.-X. and Cottenier, S.},
      title={Reproducibility in density functional theory calculations of solids},
      journal={Science},
      year={2016},
      volume={351},
      number={6280},
      doi={10.1126/science.aad3000},
      art_number={aad3000},
      note={cited By 549},
      url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962221807&doi=10.1126%2fscience.aad3000&partnerID=40&md5=0ef0657c8d793671b4b6278011e25c68},
      affiliation={Center for Molecular Modeling, Ghent University, Technologiepark 903, Zwijnaarde, BE-9052, Belgium; Peter Grünberg Institute, Institute for Advanced Simulation, Forschungszentrum Jülich, JARA (Jülich Aachen Research Alliance), Jülich, D-52425, Germany; Department of Physics, Åbo Akademi, Turku, FI-20500, Finland; Centre of Excellence in Computational Nanoscience (COMP), Department of Applied Physics, Aalto University School of Science, Post Office Box 11100, Aalto, FI-00076, Finland; Institute of Materials Chemistry, Vienna University of Technology, Getreidemarkt 9/165-TC, Vienna, A-1060, Austria; Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708, United States; Université Grenoble Alpes, Institut Nanosciences et Cryogénie-Modeling and Material Exploration Department (INAC-MEM), Laboratoire de Simulation Atomistique (L-Sim), Grenoble, F-38042, France; Commissariat À l'Énergie Atomique et Aux Énergies Alternatives (CEA), INAC-MEM, L-Sim, Grenoble, F-38054, France; Theory and Simulation of Materials (THEOS), National Centre for Computational Design, Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland; Department of Physics, University of Durham, Durham, DH1 3LE, United Kingdom; International School for Advanced Studies (SISSA), DEMOCRITOS, Consiglio Nazionale Delle Ricerche-Istituto Officina Dei Materiali (CNR-IOM), Via Bonomea 265, Trieste, I-34136, Italy; Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, Halle, D-06120, Germany; Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Post Office Box 516, Uppsala, SE-75120, Sweden; Institut für Physik and Integrative Research Institute for the Sciences (IRIS)-Adlershof, Humboldt-Universität zu Berlin, Zum Großen Windkanal 6, Berlin, D-12489, Germany; Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, Berlin, D-14195, Germany; Center for Atomic-Scale Materials Design, Department of Physics, Technical University of Denmark, Kongens Lyngby, DK-2800, Denmark; Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, United States; Department of Mathematics, Computer Science, and Physics, University of Udine, Via delle Scienze 206, Udine, I-33100, Italy; Institute of Condensed Matter, Nanosciences-Nanoscopic Physics (NAPS), Université Catholique de Louvain, Chemin des Étoiles 8, Louvain-la-Neuve, BE-1348, Belgium; Institut für Physik, Universität Basel, Klingelbergstrasse 82, Basel, CH-4056, Switzerland; School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, United States; Department of Computer Science, University of California-Davis, Davis, CA 95616, United States; Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854-8019, United States; Mat-Sim Research, Post Office Box 742, Murray Hill, NJ 07974, United States; Department of Physics, University of York, Heslington, York, YO10 5DD, United Kingdom; Department of Physics, Wake Forest University, Winston-Salem, NC 27109, United States; Scientific Computing Department, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, OX11 0QX, United Kingdom; CEA, DAM, DIF, Arpajon, F-91297, France; D