Collective and tracer diffusion of lattice gases in lattices with site-energy disorder

Abstract

Collective and tracer diffusion of lattice gases of arbitrary concentrations were investigated in one-, two-, and three-dimensional lattices with randomly distributed site energies. A model with two different site energies and varying concentrations of the trap sites was employed. A vectorizable computer code has been used for the simulation of the lattice gas with site exclusion. For low particle concentrations, the diffusion coefficient is given by the wellknown single-particle value. For larger particle concentrations and moderate concentrations of deep traps, reduced diffusion of the lattice gas in a background of randomly blocked sites is observed. For larger trap concentrations, when the concentration of the non-trap sites is smaller than the corresponding percolation threshold, the diffusion coefficient is practically independent of the particle concentration and given by the single-particle value in the disordered lattice. In one-dimensional systems one finds this behavior approximately at all trap concentrations.