An efficient method for computing collective diffusion in a strongly interacting lattice gas

An efficient numerical method for the calculation of the collective diffusion coefficient is developed. The method is based on the Bortz–Kalos–Lebowitz algorithm, with local updating of the particle lists for each process, coupled to the memory expansion for the calculation of the center-of-mass diffusion coefficient. The method is applied to the diffusion in a two-dimensional lattice gas model of square symmetry with repulsive lateral interactions. The numerical results are compared to two popular approximations, the Darken equation and the dynamical mean-field theory, whose respective merits are discussed. Finally, the decay of the dynamic structure factor with time is investigated.