The subsonic motion of a fast-moving, extended screw dislocation in a face-centered cubic metal under constant stress was studied using continuum linear elastic dislocation theory and simulation. In this regime, many phenomena predicted by the theory were shown to prevail in simulation, in particular, relativistic effects and stress orientation effects. Due to the former, the fault width was found to contract as it moves faster up to about 80% of the shear wave speed, beyond which a turning point occurred preventing it from constricting to a perfect one as speed increased further. The stress orientation effect, which was first introduced by Nabarro (1966), was demonstrated here to manifest when the shear stress resolved in the direction of motion and glide plane became high. A simple analytical expression for the steady-state fault width accounting for both stress orientation and relativistic effects was presented. In molecular dynamics simulations under arbitrary stress states, both the dislocation velocity and separation width achieve a quasi-steady state, about which they oscillate with an amplitude and frequency that reduced with speed. The separation width oscillates about a value close to that predicted by the new analytical expression. The drag coefficient was found to linearly increase with speed for speeds greater than 20% of the shear wave speed.

Stress Orientation and Relativistic Effects on the Separation of Moving Screw Dislocations. Z.Q.Wang, I.J.Beyerlein: Physical Review B, 2008, 77[18], 184112