Diffusion coefficients of an interacting lattice gas beyond the quasichemical approximation

A method for regular improvement of the mean field approximations for latti ce systems is proposed. The method requires transcription of the initial la ttice to a new lattice of complex sites each representing the states of sev eral initial sites. This approach is valuable for the description of many-p article distributions on the lattice. The validity of this approach is test ed by comparison of the coexistence curve, the concentration dependence of the probabilities for two lattice sites to be vacant and the jump diffusion coefficients for two-dimensional square lattice gas with Monte Carlo simul ation data. (C) 1999 Elsevier Science B.V. All rights reserved.