Surface diffusion in a system of particles, adsorbed onto a square lattice with 2 non-equivalent sites, was investigated. Analytical expressions for the chemical diffusion coefficient were derived in the case of strong inhomogeneity of the lattice. It was shown that the nature of the particle migration depended markedly upon the relationship between the jump frequencies. When the frequencies differed insignificantly, particle diffusion proceeded via single uncorrelated jumps between nearest-neighbor lattice sites. When the jump frequencies differed appreciably (slow and fast jumps), transfer of particles over the surface proceeded via pairs of consecutive jumps. A slow jump was followed by a fast jump. There were 2 types of these jump pairs. The coverage dependences of the tracer, jump and chemical diffusion coefficients were calculated for the Langmuir lattice gas, at representative temperatures, by using analytical and numerical approaches. The agreement of the results, obtained by using the 2 different methods, was quite good.

Surface Diffusion on a Square Lattice with Two Non-Equivalent Sites. N.A.Tarasenko, A.A.Tarasenko, Z.Bryknar, L.Jastrabik: Surface Science, 2004, 562[1-3], 22-32