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

LM Hale and JA Zimmerman and CR Weinberger, COMPUTATIONAL MATERIALS SCIENCE, 90, 106-115 (2014).

DOI: 10.1016/j.commatsci.2014.03.064

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.

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