Diffusion of interacting particles in metals based on the quantum-lattice-gas model

We study the hopping motion of interacting particles in metals by assuming the nonadiabatic response of conduction electrons and phonons to the hopping motion. The mutual interaction between particles is described by the lattice-gas model with nearest-neighbor interaction. In order to study the effect of the mutual interaction on a particle hopping, we calculate their average jump rate, taking account of the average distribution of the nearest-neighboring particles before and after the hopping. At low temperatures, the average jump rate is mainly determined by the nonadiabatic response of conduction electrons. We find that this jump rate consists of two contributions, temperature dependent and temperature independent. The former is similar to the muon jump rate in Cu, which is proportional to some power of the temperature, and the latter is due to the effect of the interaction between interstitial particles. At high temperatures, the average jump rate is obtained from the small-polaron model. We find that this jump rate is thermally activated and its activation energy is lower than that of the noninteracting-particle system.