The kink-nucleation process in body-centered cubic screw dislocations was examined using atomistic simulation and transition pathway analysis, with particular emphasis placed upon the compact core structure. The existence of a threshold stress was observed which resulted in an abrupt change in the minimum energy path of the kink-nucleation process, and hence, in a discontinuity in the activation energy versus stress relationship for the process. The magnitude of the discontinuity was found to be related to the degree of metastability of an intermediate split-core structure. This feature appeared to be a direct consequence of the so-called camel-hump nature of the Peierls potential, which manifests itself in the existence of a metastable, intermediate split-core structure. The effect was observed in a number of empirical EAM potentials, including Fe, Ta, V, Nb and Mo, suggesting a generality to the observations.

Screw Dislocation Mobility in BCC Metals: the Role of the Compact Core on Double-Kink Nucleation. P.A.Gordon, T.Neeraj, Y.Li, J.Li: Modelling and Simulation in Materials Science and Engineering, 2010, 18[8], 085008