Simulations of bcc tantalum screw dislocations: Why classical inter-atomic potentials predict {1 1 2} slip

A thorough molecular dynamics study is performed to investigate the predicted {1 1 2} 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 {1 1 2} slip, while a non-polarized core is expected to slip on {1 1 0} planes. Here, results from five different potentials for tantalum are presented as they all show slip to be primarily active along {1 1 2} planes even though the stable core structure is non-polar. This {1 1 2} slip occurs through dislocation glide on two different {1 1 0} planes due to the presence of a metastable split core structure, and regardless of the relative magnitudes of resolved shear stresses for the two {1 1 0} 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.