Supersonic dislocation kinetics from an augmented Peierls model

The controversial issue of whether dislocations can travel faster than shea r or longitudinal waves is investigated. The Peierls model, modified to acc ount for drag and gradient effects, furnishes a kinetic relation between th e applied shear stress and speed of uniformly moving dislocations. This rel ation predicts intersonic and supersonic speeds at high enough stress, but also regimes of unstable motion, in agreement with recent atomistic simulat ions.