Diffusion in concentrated lattice gases. II. Particles with attractive nearest-neighbor interaction on three-dimensional lattices

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Abstract
The diffusion process of particles in concentrated lattice gases is investigated, with the assumption of a fcc lattice and nearest-neighbor attraction (but double occupancy of sites being forbidden). Both the self-diffusion of tagged particles and the collective diffusion, by which concentration fluctuations decay, are studied. Apart from a mean-field treatment, the various diffusion coefficients are estimated by Monte Carlo techniques and interpreted in terms of static long- and short-range order (i.e., unmixing) occurring in this model system. Collective diffusion is studied by direct simulation of linear response to wave-vector-dependent "fields." Near the critical temperature, pronounced critical slowing down of the collective diffusion coefficient is observed. The self-diffusion constant stays finite but exhibits a singularity of its slope. The correlation factor for self-diffusion is found to be practically independent of temperature. A qualitative discussion of the behavior inside of the mixed-phase region is also given.