- The kinematics and kinetics of edge and screw dislocations in FCC materials were studied by molecular dynamics, with Cu as a case study. It was found that with increasing stress screw dislocations enter into the transonic regime continuously and that they remain stable up to a velocity of about 2.2 km s− 1. Edge dislocations are limited by the transverse sound velocity at low stresses and discontinuously cross into the transonic regime at higher stresses. For sufficiently long edge dislocations, the subsonic–transonic transition is initiated by an athermal nucleation process. Finally, an expression for the velocity dependence of the dislocation mobility was derived.