The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Yury Mishin - One of the best experts on this subject based on the ideXlab platform.
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Unraveling the Dislocation Core structure at a van der Waals gap in bismuth telluride.
arXiv: Materials Science, 2019Co-Authors: Douglas L. Medlin, Catalin D. Spataru, L. M. Hale, N Yang, Yury MishinAbstract:Tetradymite-structured chalcogenides such as bismuth telluride Bi_{2}Te_{3} are of significant interest for thermoelectric energy conversion and as topological insulators. Dislocations play a critical role during synthesis and processing of such materials and can strongly affect their functional properties. The Dislocations between quintuple layers present special interest since their Core structure is controlled by the van der Waals interactions between the layers. In this work, using atomic-resolution electron microscopy, we resolve the basal Dislocation Core structure in Bi_{2}Te_{3}, quantifying the disregistry of the atomic planes across the Core. We show that, despite the existence of a stable stacking fault in the basal plane gamma surface, the Dislocation Core spreading is mainly due to the weak bonding between the layers, which leads to a small energy penalty for layer sliding parallel to the van der Waals gap. Calculations within a semidiscrete variational Peierls-Nabarro model informed by first-principles calculations support our experimental findings.
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Unraveling the Dislocation Core structure at a van der Waals gap in bismuth telluride
Nature Communications, 2019Co-Authors: Douglas L. Medlin, Catalin D. Spataru, L. M. Hale, N Yang, Yury MishinAbstract:The atomic level Core structure of Dislocations in non-metallic materials such as chalcogenides remains elusive. Here, the authors combine atomic-resolution electron microscopy and simulations to image a Dislocation Core in bismuth telluride and show it spreads because of weak bonding between atomic layers.AbstractTetradymite-structured chalcogenides such as bismuth telluride (Bi_2Te_3) are of significant interest for thermoelectric energy conversion and as topological insulators. Dislocations play a critical role during synthesis and processing of such materials and can strongly affect their functional properties. The Dislocations between quintuple layers present special interest since their Core structure is controlled by the van der Waals interactions between the layers. In this work, using atomic-resolution electron microscopy, we resolve the basal Dislocation Core structure in Bi_2Te_3, quantifying the disregistry of the atomic planes across the Core. We show that, despite the existence of a stable stacking fault in the basal plane gamma surface, the Dislocation Core spreading is mainly due to the weak bonding between the layers, which leads to a small energy penalty for layer sliding parallel to the van der Waals gap. Calculations within a semidiscrete variational Peierls-Nabarro model informed by first-principles calculations support our experimental findings.
S. H. Zhang - One of the best experts on this subject based on the ideXlab platform.
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pnadis an automated peierls nabarro analyzer for Dislocation Core structure and slip resistance
Computer Physics Communications, 2019Co-Authors: S. H. Zhang, Dominik Legut, R F ZhangAbstract:Abstract Dislocation is one of the most critical and fundamental crystal defects that dominate the mechanical behavior of crystalline solids, however, a quantitative determination of its character and property in experiments is quite challenging and limited so far. In this paper, a fully automated Peierls–Nabarro (P–N) analyzer named PNADIS is presented; a complete set of the character and property of Dislocation can be automatically derived, including the Dislocation Core structure, Peierls energy and stress, pressure field around Dislocation Core, solute/Dislocation interaction energy, as well as the energy barrier and increase in critical-resolved shear stress at 0 K for solid solution strengthening. Furthermore, both one-dimensional (1D) and two-dimensional (2D) P–N models are implemented to meet the demand to analyze the character and property of Dislocation for not only simple FCC and HCP structures but also complex crystals. The implementation of this code has been critically validated by a lot of evaluations and tests including 1D P–N model for complex crystals, 2D P–N model for FCC and HCP metals, pressure field around Dislocation Core, and solid solution strengthening for alloys. We expect that the automated feature of this code would provide a high-efficiency solution for determining the character and property of Dislocation. Program summary Program title: PNADIS Program Files doi: http://dx.doi.org/10.17632/whk6wdy3nn.1 Licensing provisions: GNU General Public License 3 Programming language: MATLAB Nature of problem: To determine automatically the character and property of Dislocation, including Dislocation Core structure, Peierls stress, pressure field around Dislocation Core and solid solution strengthening, for not only FCC and HCP structures but also complex crystals. Solution method: The generalized stacking fault energy is firstly fitted by Fourier expansion, and meanwhile an appropriate trial function of disregistry vector is chosen. Afterwards, a least square minimization of the difference between elastic resistance and restoring force for one-dimensional Peierls–Nabarro model, or a global minimization of the total Dislocation energy via particle swarm optimization or genetic algorithm for two-dimensional Peierls–Nabarro model, will be performed to determine the Dislocation Core structure of complex crystals, or FCC and HCP structures. Finally, the Peierls stress, pressure field around Dislocation Core and solid solute strengthening are derived from the calculated Dislocation Core structure.
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PNADIS: An automated Peierls–Nabarro analyzer for Dislocation Core structure and slip resistance
Computer Physics Communications, 2019Co-Authors: S. H. Zhang, Dominik Legut, Ruifeng ZhangAbstract:Abstract Dislocation is one of the most critical and fundamental crystal defects that dominate the mechanical behavior of crystalline solids, however, a quantitative determination of its character and property in experiments is quite challenging and limited so far. In this paper, a fully automated Peierls–Nabarro (P–N) analyzer named PNADIS is presented; a complete set of the character and property of Dislocation can be automatically derived, including the Dislocation Core structure, Peierls energy and stress, pressure field around Dislocation Core, solute/Dislocation interaction energy, as well as the energy barrier and increase in critical-resolved shear stress at 0 K for solid solution strengthening. Furthermore, both one-dimensional (1D) and two-dimensional (2D) P–N models are implemented to meet the demand to analyze the character and property of Dislocation for not only simple FCC and HCP structures but also complex crystals. The implementation of this code has been critically validated by a lot of evaluations and tests including 1D P–N model for complex crystals, 2D P–N model for FCC and HCP metals, pressure field around Dislocation Core, and solid solution strengthening for alloys. We expect that the automated feature of this code would provide a high-efficiency solution for determining the character and property of Dislocation. Program summary Program title: PNADIS Program Files doi: http://dx.doi.org/10.17632/whk6wdy3nn.1 Licensing provisions: GNU General Public License 3 Programming language: MATLAB Nature of problem: To determine automatically the character and property of Dislocation, including Dislocation Core structure, Peierls stress, pressure field around Dislocation Core and solid solution strengthening, for not only FCC and HCP structures but also complex crystals. Solution method: The generalized stacking fault energy is firstly fitted by Fourier expansion, and meanwhile an appropriate trial function of disregistry vector is chosen. Afterwards, a least square minimization of the difference between elastic resistance and restoring force for one-dimensional Peierls–Nabarro model, or a global minimization of the total Dislocation energy via particle swarm optimization or genetic algorithm for two-dimensional Peierls–Nabarro model, will be performed to determine the Dislocation Core structure of complex crystals, or FCC and HCP structures. Finally, the Peierls stress, pressure field around Dislocation Core and solid solute strengthening are derived from the calculated Dislocation Core structure.
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First-principles investigation of strain effects on the stacking fault energies, Dislocation Core structure, and Peierls stress of magnesium and its alloys
Physical Review B, 2017Co-Authors: S. H. Zhang, Irene J. Beyerlein, Dominik Legut, Zuoguang Zhang, Shun-li Shang, Zi-kui Liu, Timothy C. Germann, Ruifeng ZhangAbstract:Taking pure Mg, Mg-Al, and Mg-Zn as prototypes, the effects of strain on the stacking fault energies (SFEs), Dislocation Core structure, and Peierls stress were systematically investigated by means of density functional theory and the semidiscrete variational Peierls-Nabarro model. Our results suggest that volumetric strain may significantly influence the values of SFEs of both pure Mg and its alloys, which will eventually modify the Dislocation Core structure, Peierls stress, and preferred slip system, in agreement with recent experimental results. The so-called "strain factor" that was previously proposed for the solute strengthening could be justified as a major contribution to the strain effect on SFEs. Based on multivariate regression analysis, we proposed universal exponential relationships between the Dislocation Core structure, the Peierls stress, and the stable or unstable SFEs. Electronic structure calculations suggest that the variations of these critical parameters controlling strength and ductility under strain can be attributed to the strain-induced electronic polarization and redistribution of valence charge density at hollow sites. These findings provide a fundamental basis for tuning the strain effect to design novel Mg alloys with both high strength and ductility.Web of Science9522art. no. 22410
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first principles investigation of strain effects on the stacking fault energies Dislocation Core structure and peierls stress of magnesium and its alloys
Physical Review B, 2017Co-Authors: S. H. Zhang, Irene J. Beyerlein, Dominik Legut, Zuoguang Zhang, Shun-li Shang, Zi-kui Liu, Timothy C. Germann, R F ZhangAbstract:Taking pure Mg, Mg-Al, and Mg-Zn as prototypes, the effects of strain on the stacking fault energies (SFEs), Dislocation Core structure, and Peierls stress were systematically investigated by means of density functional theory and the semidiscrete variational Peierls-Nabarro model. Our results suggest that volumetric strain may significantly influence the values of SFEs of both pure Mg and its alloys, which will eventually modify the Dislocation Core structure, Peierls stress, and preferred slip system, in agreement with recent experimental results. The so-called ``strain factor'' that was previously proposed for the solute strengthening could be justified as a major contribution to the strain effect on SFEs. Based on multivariate regression analysis, we proposed universal exponential relationships between the Dislocation Core structure, the Peierls stress, and the stable or unstable SFEs. Electronic structure calculations suggest that the variations of these critical parameters controlling strength and ductility under strain can be attributed to the strain-induced electronic polarization and redistribution of valence charge density at hollow sites. These findings provide a fundamental basis for tuning the strain effect to design novel Mg alloys with both high strength and ductility.
Douglas L. Medlin - One of the best experts on this subject based on the ideXlab platform.
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Unraveling the Dislocation Core structure at a van der Waals gap in bismuth telluride.
arXiv: Materials Science, 2019Co-Authors: Douglas L. Medlin, Catalin D. Spataru, L. M. Hale, N Yang, Yury MishinAbstract:Tetradymite-structured chalcogenides such as bismuth telluride Bi_{2}Te_{3} are of significant interest for thermoelectric energy conversion and as topological insulators. Dislocations play a critical role during synthesis and processing of such materials and can strongly affect their functional properties. The Dislocations between quintuple layers present special interest since their Core structure is controlled by the van der Waals interactions between the layers. In this work, using atomic-resolution electron microscopy, we resolve the basal Dislocation Core structure in Bi_{2}Te_{3}, quantifying the disregistry of the atomic planes across the Core. We show that, despite the existence of a stable stacking fault in the basal plane gamma surface, the Dislocation Core spreading is mainly due to the weak bonding between the layers, which leads to a small energy penalty for layer sliding parallel to the van der Waals gap. Calculations within a semidiscrete variational Peierls-Nabarro model informed by first-principles calculations support our experimental findings.
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Unraveling the Dislocation Core structure at a van der Waals gap in bismuth telluride
Nature Communications, 2019Co-Authors: Douglas L. Medlin, Catalin D. Spataru, L. M. Hale, N Yang, Yury MishinAbstract:The atomic level Core structure of Dislocations in non-metallic materials such as chalcogenides remains elusive. Here, the authors combine atomic-resolution electron microscopy and simulations to image a Dislocation Core in bismuth telluride and show it spreads because of weak bonding between atomic layers.AbstractTetradymite-structured chalcogenides such as bismuth telluride (Bi_2Te_3) are of significant interest for thermoelectric energy conversion and as topological insulators. Dislocations play a critical role during synthesis and processing of such materials and can strongly affect their functional properties. The Dislocations between quintuple layers present special interest since their Core structure is controlled by the van der Waals interactions between the layers. In this work, using atomic-resolution electron microscopy, we resolve the basal Dislocation Core structure in Bi_2Te_3, quantifying the disregistry of the atomic planes across the Core. We show that, despite the existence of a stable stacking fault in the basal plane gamma surface, the Dislocation Core spreading is mainly due to the weak bonding between the layers, which leads to a small energy penalty for layer sliding parallel to the van der Waals gap. Calculations within a semidiscrete variational Peierls-Nabarro model informed by first-principles calculations support our experimental findings.
G Nouet - One of the best experts on this subject based on the ideXlab platform.
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a new atomistic model for the threading screw Dislocation Core in wurtzite gan
Computational Materials Science, 2012Co-Authors: I Belabbas, J Chen, G NouetAbstract:We report a new atomistic model for the threading screw Dislocation Core in wurtzite gallium nitride. By combining elasticity theory and atomistic simulations, we have revealed the new Core configuration, with a double 6-atoms ring structure, to be more energetically favourable than the previously known one with a single 6-atoms ring structure, introduced about ten years ago. The new Core configuration is fully coordinated and has both Ga–Ga and N–N homo-nuclear bonds in its centre. As the double 6-atoms ring Core is free from dangling bonds, it was found to introduce less dispersed energy levels in the bandgap than the single 6-atoms ring Core.
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atomistic modeling of the a c mixed Dislocation Core in wurtzite gan
Physical Review B, 2007Co-Authors: I Belabbas, A Bere, J Chen, S Petit, Akli M Belkhir, P Ruterana, G NouetAbstract:An atomistic simulation of the threading $(\mathbf{a}+\mathbf{c})$-mixed Dislocation Core in wurtzite GaN has been carried out. Starting from models generated in the framework of continuum elasticity theory, two Core configurations are obtained independently by using an empirical potential and a tight-binding based ab initio method. The most energetically favorable Core with a $5∕7$-atoms ring structure is fully coordinated without wrong bonds, whereas the other with a complex double $5∕6$-atoms ring structure contains two rows of dangling bonds. Both Core configurations introduce empty states spread over the upper half of the band gap.
R F Zhang - One of the best experts on this subject based on the ideXlab platform.
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pnadis an automated peierls nabarro analyzer for Dislocation Core structure and slip resistance
Computer Physics Communications, 2019Co-Authors: S. H. Zhang, Dominik Legut, R F ZhangAbstract:Abstract Dislocation is one of the most critical and fundamental crystal defects that dominate the mechanical behavior of crystalline solids, however, a quantitative determination of its character and property in experiments is quite challenging and limited so far. In this paper, a fully automated Peierls–Nabarro (P–N) analyzer named PNADIS is presented; a complete set of the character and property of Dislocation can be automatically derived, including the Dislocation Core structure, Peierls energy and stress, pressure field around Dislocation Core, solute/Dislocation interaction energy, as well as the energy barrier and increase in critical-resolved shear stress at 0 K for solid solution strengthening. Furthermore, both one-dimensional (1D) and two-dimensional (2D) P–N models are implemented to meet the demand to analyze the character and property of Dislocation for not only simple FCC and HCP structures but also complex crystals. The implementation of this code has been critically validated by a lot of evaluations and tests including 1D P–N model for complex crystals, 2D P–N model for FCC and HCP metals, pressure field around Dislocation Core, and solid solution strengthening for alloys. We expect that the automated feature of this code would provide a high-efficiency solution for determining the character and property of Dislocation. Program summary Program title: PNADIS Program Files doi: http://dx.doi.org/10.17632/whk6wdy3nn.1 Licensing provisions: GNU General Public License 3 Programming language: MATLAB Nature of problem: To determine automatically the character and property of Dislocation, including Dislocation Core structure, Peierls stress, pressure field around Dislocation Core and solid solution strengthening, for not only FCC and HCP structures but also complex crystals. Solution method: The generalized stacking fault energy is firstly fitted by Fourier expansion, and meanwhile an appropriate trial function of disregistry vector is chosen. Afterwards, a least square minimization of the difference between elastic resistance and restoring force for one-dimensional Peierls–Nabarro model, or a global minimization of the total Dislocation energy via particle swarm optimization or genetic algorithm for two-dimensional Peierls–Nabarro model, will be performed to determine the Dislocation Core structure of complex crystals, or FCC and HCP structures. Finally, the Peierls stress, pressure field around Dislocation Core and solid solute strengthening are derived from the calculated Dislocation Core structure.
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first principles investigation of strain effects on the stacking fault energies Dislocation Core structure and peierls stress of magnesium and its alloys
Physical Review B, 2017Co-Authors: S. H. Zhang, Irene J. Beyerlein, Dominik Legut, Zuoguang Zhang, Shun-li Shang, Zi-kui Liu, Timothy C. Germann, R F ZhangAbstract:Taking pure Mg, Mg-Al, and Mg-Zn as prototypes, the effects of strain on the stacking fault energies (SFEs), Dislocation Core structure, and Peierls stress were systematically investigated by means of density functional theory and the semidiscrete variational Peierls-Nabarro model. Our results suggest that volumetric strain may significantly influence the values of SFEs of both pure Mg and its alloys, which will eventually modify the Dislocation Core structure, Peierls stress, and preferred slip system, in agreement with recent experimental results. The so-called ``strain factor'' that was previously proposed for the solute strengthening could be justified as a major contribution to the strain effect on SFEs. Based on multivariate regression analysis, we proposed universal exponential relationships between the Dislocation Core structure, the Peierls stress, and the stable or unstable SFEs. Electronic structure calculations suggest that the variations of these critical parameters controlling strength and ductility under strain can be attributed to the strain-induced electronic polarization and redistribution of valence charge density at hollow sites. These findings provide a fundamental basis for tuning the strain effect to design novel Mg alloys with both high strength and ductility.