Lattice wave emission from a moving dislocation

Abstract

A dislocation moving in a lattice accelerates and decelerates due to the lattice periodicity and emits lattice waves. Simulations of this process in square and triangular lattices have been presented. Under a small stress, less than 70--80 % of the Peierls stress, a dislocation moving from an unstable position cannot overcome the next Peierls hill because it loses energy by emitting lattice waves. With a larger stress a long-distance motion of a dislocation is possible. When a dislocation moves slowly, lattice waves of dipolar type are emitted in the direction perpendicular to the motion of the dislocation. When the dislocation velocity is about half of the shear wave velocity, a V-shaped pattern of strong lattice vibration forms behind the moving dislocation because of the restricted propagation directions of the excited lattice waves. When the dislocation velocity exceeds 70% of the shear wave velocity, pair creation of dislocations occurs, which leads to dislocation cascading. A dislocation can move faster than the shear wave velocity in the square lattice, and there is no discontinuous change between subsonic and supersonic motions. The dislocation velocity is not proportional to the applied stress. The energy loss of the moving dislocation is about one order of magnitude larger than the theoretical value estimated by phonon-scattering mechanisms, even at room temperature.