Structure and mobility of the 1/2 <111> {112} edge dislocation in BCC iron studied by molecular dynamics

In this paper, we carried out atomistic calculations to investigate in detail the core structure and motion mechanism of the 1/2 < 11 (1) over bar > {112} edge dislocation in alpha-iron. First, molecular statics simulations are used to characterise the dislocation-core structure in the framework of the Peierls-Nabarro model. It is shown that the accommodation of the distortion due to the insertion of the extra half-planes is not equivalent in the planes above and below the dislocation slip plane and that the relative atomic-displacement profile in the dislocation-core region is asymmetrical. Then. molecular dynamics simulations are Used to study the mechanism of the dislocation motion at different temperatures. At low temperature, the dislocation is found to move by nucleation and propagation of kink-pairs along its line. Independently of temperature, when loading is performed in the twinning direction, the critical stress is found to be lower than the one corresponding to the antitwinning loading direction. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.