Diffusion in generalized lattice-gas models

A technique has been developed to calculate the exact diffusion tensor for the lattice-gas model in the low-concentration limit for any complex elementary cell. The analysis takes into account the detailed structure of the elementary cell and the structure of the diffusion barrier. The technique is also applicable to non-Markoff diffusion and, consequently, can include polaronic and inertia effects. The calculation reduces to simple matrix-algebraic operations which may be carried out analytically in many cases. Applications to some one- and two-dimensional models are described, including disordered systems and non-Markoff diffusion, in structures with complex elementary cells.