Thermal Effects on Dislocation Velocities in a Linear Chain

The effects of the thermal motion of atoms upon a dislocation in steady motion in a modified Frenkel-Kontorowa model are examined. The energy associated with the localized mode due to the dislocation and the energy associated with the nonlocalized modes are considered separately and referred to as the energy of the dislocation system and of the surrounding heat bath, respectively. Several distinct components of the net energy exchange between dislocation system and heat bath are isolated. In particular, one component is found which may be described as a coordinating effect between the thermal motion of the atoms and the dislocation motion, which results in a transfer of energy from the heat bath to the moving dislocation. When model parameter values are chosen so that this component of energy transfer is dominant, the drag on a moving dislocation in the model studied decreases with increase in temperature. Computer simulation of the model lends support to the principal features of the theory.