The structure of high-velocity screw dislocations in Cu was investigated using molecular dynamics. It was observed that the dissociation width of the dislocation into its partials was velocity-dependent and 2 main regimes, at low and high velocities with respect to the shear wave velocity, were identified. In the first regime the drag coefficient of the dislocation was temperature dependent and the dissociation width decreased with the velocity. In the second regime the drag coefficient was an order of magnitude higher than in the first regime and was temperature independent. In this regime the trailing partial spread from the slip plane onto the cross-slip plane and the dislocation core became non-planar. Due to this non-planar structure, the dislocation widens as the velocity increased and the partial separation became unstable at velocities above 0.67 times the shear wave velocity. An elastic-continuum model was derived for the gliding dislocation structure.

Non-Planar Core and Dynamical Behavior of Screw Dislocations in Copper at High Velocities. D.Mordehai, I.Kelson, G.Makov: Physical Review B, 2006, 74[18], 184115 (9pp)