Constrained Nudged Elastic Band calculation of the Peierls barrier with atomic relaxations

0385257 - ÚFM 2013 RIV GB eng J - Journal Article
Gröger, Roman - Vitek, V.
Constrained Nudged Elastic Band calculation of the Peierls barrier with atomic relaxations.
Modelling and Simulation in Materials Science and Engineering. Roč. 20, č. 3 (2012), 035019. ISSN 0965-0393. E-ISSN 1361-651X
R&D Projects: GA ČR GAP204/10/0255; GA MŠMT(CZ) ED1.1.00/02.0068
Institutional research plan: CEZ:AV0Z20410507
Keywords : dislocation * Peierls barrier * Nudged Elastic Band
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 1.932, year: 2012

We demonstrate that the straightforward application of the nudged elastic band (NEB) method does not determine the correct Peierls barrier of 1/2111 screw dislocations in bcc metals. Although this method guarantees that the states (images) of the system are distributed uniformly along the minimum energy path, it does not imply that the dislocation positions are distributed uniformly along this path. In fact, clustering of dislocation positions near potential minima occurs which leads to an overestimate of both the slope of the Peierls barrier and the Peierls stress. We propose a modification in which the NEB method is applied only to a small number of degrees of freedom that determine the position of the dislocation, while all other coordinates of atoms are relaxed by molecular statics as in any atomistic study. This modified NEB method with relaxations gives the Peierls barrier that increases smoothly with the dislocation position and the corresponding Peierls stress agrees well with that evaluated by the direct application of stress in the atomistic modeling of the dislocation glide.
Permanent Link: http://hdl.handle.net/11104/0215223