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Atomistic simulations of kinks in 1/2a<111> screw dislocations in bcc tantalum

Wang, Guofeng and Strachan, Alejandro and Çağin, Tahir and Goddard, William A., III (2003) Atomistic simulations of kinks in 1/2a<111> screw dislocations in bcc tantalum. Physical Review B, 68 (22). Art. No. 224101. ISSN 0163-1829. http://resolver.caltech.edu/CaltechAUTHORS:WANprb03b

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Abstract

Two types of equilibrium core structures (denoted symmetric and asymmetric) for 1/2a<111> screw dislocations in bcc metals have been found in atomistic simulations. In asymmetric (or polarized) cores, the central three atoms simultaneously translate along the Burgers vector direction. This collective displacement of core atoms is called polarization. In contrast, symmetric (nonpolarized) cores have zero core polarization. To examine the possible role of dislocation core in kink-pair formation process, we studied the multiplicity, structural features, and formation energies of 1/3a<112> kinks in 1/2a<111> screw dislocations with different core structures. To do this we used a family of embedded atom model potentials for tantalum (Ta) all of which reproduce bulk properties (density, cohesive energy, and elastic constants) from quantum mechanics calculations but differ in the resulting polarization of 1/2a<111> screw dislocations. For dislocations with asymmetric core, there are two energy equivalent core configurations [with positive (P) and negative (N) polarization], leading to 2 types of (polarization) flips, 8 kinds of isolated kinks, and 16 combinations of kink pairs. We find there are only two elementary kinks, while the others are composites of elementary kinks and flips. In contrast, for screw dislocations with symmetric core, there are only two types of isolated kinks and one kind of kink pair. We find that the equilibrium dislocation core structure of 1/2a<111> screw dislocations is an important factor in determining the kink-pair formation energy.


Item Type:Article
Additional Information:©2003 The American Physical Society (Received 16 May 2003; revised 12 August 2003; published 5 December 2003) This research was funded by a grant from DOE-ASCI-ASAP. The facilities of the MSC were also supported by grants from NSF (Grant Nos. CHE 9985574 and CHE 9977872), ARO (MURI), ARO (DURIP), Chevron-Texaco Corp., General Motors, Beckman Institute, and Asahi Kasei.
Subject Keywords:screw dislocations; tantalum; kink bands; density; lattice energy; elastic constants
Record Number:CaltechAUTHORS:WANprb03b
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:WANprb03b
Alternative URL:http://dx.doi.org/10.1103/PhysRevB.68.224101
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6168
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:27 Nov 2006
Last Modified:26 Dec 2012 09:18

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