Simulations of bcc tantalum screw dislocations: Why classical inter-atomic potentials predict {112} slip

A thorough molecular dynamics study is performed to investigate the predicted {112} yield behavior associated with the slip of a single screw dislocation using classical atomistic potentials of body-centered cubic metals. Previous works have drawn an association between the structure of the stable screw dislocation core and the resulting slip nature showing that a polarized core can lead to {112} slip, while a non-polarized core is expected to slip on {110} planes. Here, results from five different potentials for tantalum are presented as they all show slip to be primarily active along {112} planes even though the stable core structure is non-polar. This {112} slip occurs through dislocation glide on two different {110} planes due to the presence of a metastable split core structure, and regardless of the relative magnitudes of resolved shear stresses for the two {110} planes. Further investigations shows that the split core structure, an artifact of the atomic potentials used, also influences slip behavior associated with dynamic motion of kinked dislocations in ambient temperature simulations. (C) 2014 Elsevier B. V. All rights reserved.