Diffusion of lattice gases in disordered lattices

Abstract

A survey of recent simulations and analytical work on collective diffusion of lattice gases in lattices with site-energy disorder is given. In one-dimensional disordered lattices, exact results have been obtained in the limit of small and large particle concentrations. Simulation results at intermediate concentrations show that the time-dependent site-occupancy correlations are not yet satisfactorily understood. In higher-dimensional disordered lattices, an effective-medium theory, which uses mean-field transition rates, gives an improvement over the phenomenological description and qualitative agreement with the simulations. The main effects derive from saturation of deep trapping sites. One conspicuous example is the existence of a coefficient of collective diffusion in a situation where no single-particle diffusion coefficient exists.