Molecular dynamics simulations were used to describe the acceleration and motion of dissociated dislocations in copper to extreme velocities. Stationary dislocations were accelerated either by shear stress or by shear strain rates. Results indicate that dislocations could be accelerated into transonic and supersonic velocities. Stable dislocation motion was found in three distinguished regimes: (i) in a plateau of velocities close to 1.6km/s in the subsonic regime; (ii) in a narrow range of velocities around 2.6km/s in the first transonic regime; and (iii) in the second transonic regime with increasing velocities. For large velocities in the second transonic regime and in the supersonic regime, the shear stress was exceeded and dislocation motion was unstable as the crystal loses its mechanical stability. The stacking fault fluctuates around 35Å in the subsonic regime, but subsequently declines with velocity to less than half the initial value in the second transonic regime. Both the decreasing stacking fault width and the plateau of velocities in the first transonic regime, indicating the existence of a radiation-free state, were in agreement with theoretical predictions.

Molecular Dynamics Simulation of Fast Dislocations in Copper. H.Tsuzuki, P.S.Branicio, J.P.Rino: Acta Materialia, 2009, 57[6], 1843-55