Diffusion of particles on an inhomogeneous disordered square lattice with two non-equivalent sites

We investigate diffusion in a system of particles adsorbed in a square lattice with two kinds of sites. The sites are randomly distributed over the lattice. It is shown that the character of the particle migration depends substantially on the relation between the concentrations of the deep and shallow sites. The lattice inhomogeneity produces specific peculiarities in the coverage dependencies of the diffusion coefficients. We derive simple analytic expressions which describe qualitatively and even quantitatively the diffusion in such inhomogeneous disordered systems. Using kinetic Monte Carlo simulations we calculated the coverage dependencies of the isothermal susceptibility and the tracer, jump and chemical diffusion coefficients. There is a rather good coincidence of the numerical data with the analytical results.