The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
D.J. Bacon - One of the best experts on this subject based on the ideXlab platform.
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Effects of temperature on structure and mobility of the 〈100〉 edge dislocation in body-centred cubic iron
Acta Materialia, 2010Co-Authors: D.A. Terentyev, Yury N. Osetsky, D.J. BaconAbstract:Dislocation segments with Burgers vector b=〈100〉 are formed during deformation of body-centred-cubic (bcc) metals by the interaction between dislocations with b=1/2〈111〉. Such segments are also created by reactions between dislocations and dislocation loops in irradiated bcc metals. The obstacle resistance produced by these segments on gliding dislocations is controlled by their mobility, which is determined in turn by the atomic structure of their cores. The core structure of a straight 〈100〉 edge dislocation is investigated here by atomic-scale computer simulation for α-iron using three different interatomic potentials. At low temperature the dislocation has a non-planar core consisting of two 1/2〈111〉 fractional dislocations with atomic Disregistry spread on planes inclined to the main glide plane. Increasing temperature modifies this core structure and so reduces the critical applied shear stress for glide of the 〈100〉 dislocation. It is concluded that the response of the 〈100〉 edge dislocation to temperature or applied stress determines specific reaction pathways occurring between a moving dislocation and 1/2〈111〉 dislocation loops. The implications of this for plastic flow in unirradiated and irradiated ferritic materials are discussed and demonstrated by examples.
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Computer simulation of the core structure of the ???111??? screw dislocation in ??-iron containing copper precipitates: I. Structure in the matrix and a precipitate
Acta Materialia, 2002Co-Authors: Taylor Harry, D.J. BaconAbstract:Strengthening due to small coherent BCC precipitates of copper is an important component of in-service irradiation hardening of ferritic pressure-vessel steels. The dislocation effects involved are studied here by atomic-scale computer simulation. Many-body interatomic potentials for the Fe-Cu alloy system are used to investigate stacking-fault-energy surfaces and to simulate the atomic structure of the ???111??? screw dislocation in both pure ??-iron and the metastable BCC phase of copper. In iron, the core has the well-known three-fold form of atomic Disregistry. In BCC copper, however, the core becomes delocalised by transformation of the copper as the lattice parameter is reduced to mimic the strain experienced by precipitates. Simulation of the screw dislocation threading through the centre of a BCC copper precipitate in an ??-iron matrix shows that the extent of core delocalisation depends on precipitate size. The dislocation energy changes indicate a significant dislocation pinning effect due to this dislocation-induced precipitate transformation process. ?? 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
Y. 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, N. Yang, Catalin D. Spataru, L. M. Hale, Y. 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, N. Yang, Catalin D. Spataru, L. M. Hale, Y. 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.
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, N. Yang, Catalin D. Spataru, L. M. Hale, Y. 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, N. Yang, Catalin D. Spataru, L. M. Hale, Y. 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.
Taylor Harry - One of the best experts on this subject based on the ideXlab platform.
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Computer simulation of the core structure of the ???111??? screw dislocation in ??-iron containing copper precipitates: I. Structure in the matrix and a precipitate
Acta Materialia, 2002Co-Authors: Taylor Harry, D.J. BaconAbstract:Strengthening due to small coherent BCC precipitates of copper is an important component of in-service irradiation hardening of ferritic pressure-vessel steels. The dislocation effects involved are studied here by atomic-scale computer simulation. Many-body interatomic potentials for the Fe-Cu alloy system are used to investigate stacking-fault-energy surfaces and to simulate the atomic structure of the ???111??? screw dislocation in both pure ??-iron and the metastable BCC phase of copper. In iron, the core has the well-known three-fold form of atomic Disregistry. In BCC copper, however, the core becomes delocalised by transformation of the copper as the lattice parameter is reduced to mimic the strain experienced by precipitates. Simulation of the screw dislocation threading through the centre of a BCC copper precipitate in an ??-iron matrix shows that the extent of core delocalisation depends on precipitate size. The dislocation energy changes indicate a significant dislocation pinning effect due to this dislocation-induced precipitate transformation process. ?? 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
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Computer Simulation Study of the Effects of Copper Precipitates on Dislocation Core Structure in Ferritic Steels
MRS Proceedings, 1996Co-Authors: Taylor Harry, David BaconAbstract:AbstractThe small, coherent BCC precipitates of copper that form during fast neutron irradiation of ferritic steels are an important component of in-service irradiation hardening. Many-body interatomic potentials for the Fe-Cu alloy system have been developed and used to simulate the atomic structure of the ½<111> screw dislocation in both pure a-iron and the metastable BCC phase of copper. In iron, the core has the well-known 3-fold form of atomic Disregistry. In BCC copper, however, the core structure depends on the lattice parameter. At the metastable equilibrium value, the core is similar to that in iron, but as the lattice parameter is reduced, as in a precipitate, the core becomes delocalised by transformation of the copper. Simulation of dislocated crystals containing precipitates shows that the extent of this effect depends on precipitate size. The energy changes indicate a significant dislocation pinning effect due to this dislocation-induced precipitate transformation process.
L. M. Hale - 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, N. Yang, Catalin D. Spataru, L. M. Hale, Y. 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, N. Yang, Catalin D. Spataru, L. M. Hale, Y. 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.