Rate theory of dislocation motion: Thermal activation and inertial effects

A rate theory of dislocation motion is developed which incorporates both thermal activation and inertial effects and that accounts for the enhanced plasticity in superconductors. The equations of Brownian motion are applied to dislocations and are shown to describe viscous effects in thermal activation and thermal fluctuations during inertial effects. The viscosity reduces the activation rate only for high values of the damping whereas inertial effects occur only at low values. For dislocations the damping is in the range where inertial effects, and not a change in the frequency factor, occur for pure samples in the superconducting state and for dilute alloys in both the normal and superconducting state. The enhanced plasticity is therefore explained by an increase in the average distance traveled by dislocations after thermal activation accounting for the dependence on both the viscosity and the temperature.