Improved Atomistic Model of a bcc Dislocation Core

Abstract

It is shown that the strain field of a straight dislocation in an anisotropicelastic continuum includes an infinite series of terms of order 2 and higher in inverse distance from the dislocation line. These terms are determined by the nature of the core. A method is developed of finding these terms for a given dislocation while determining the core structure atomistically, using a digital computer. The equilibrium configuration of the core and the higher‐order‐term values are found rapidly by a method involving atomic force constants, which requires few calculations of interatomic forces. The model is applied to determine the core structure and near‐strain field of a 〈100〉 edge dislocation in α iron using potentials developed by Johnson and by Chang and Graham. Core structure in agreement with that found by Gehlen et al. is obtained. The results are independent of model size over a wide range, and there is agreement between strain‐energy distribution calculated atomistically and from elastic constants, for all three potentials used. The method may be useful in calculation of Peierls stress and of dislocation‐point‐defect interaction.