Low‐temperature fluctuational motion of dislocations in crystals I. Quantum and dissipative effects

Abstract

AbstractA mechanism underlying fluctuational bending of dislocation segments is considered which is based on periodical ordering in the thermal motion of atoms near the dislocation core. Basic principles of calculating the probability of dislocation unpinning from local obstacles due to the fluctuations are formulated. As found, the interaction of dislocation segments experiencing fluctuational bending with phonons and/or conduction electrons, described in the framework of the usual dissipation model, can result in a reduction of the energy of atoms near the dislocation core during the fluctuation. Consequently, the effective activation energy of the dislocation unpinning from local obstacles is increased, i.e. the mean velocity of the activated dislocation motion drops. Activated dislocation motion at low temperatures is analysed with an account of the possible quantum mechanical fluctuations which can arise in condensed structures owing to the correlation of atomic zero point vibrations. An expression is derived for the probability of low temperature fluctuational dislocation with allowance for quantum mechanical effects.