An analytical expression was derived for the surface diffusion coefficient by summing the fluxes that were due to single jump events between adjacent sites on a simple square lattice. All of the microscopic configurations of a layer of interacting particles were included at particular coverages. Using a quasi-chemical approach, nearest-neighbor particle-particle interactions were introduced by adjusting the jump rate or by modifying the probability of occurrence of particular configurations as a function of the concentration. The diffusion coefficient was found to be dominated by the latter contribution at medium and high concentrations. A comparison with the results of Monte Carlo simulations showed that an improved approximation could be achieved if the interactions were accounted for not only by changes in the activation energy for diffusion, but also by their effect upon the equilibrium distribution of particles.

P.Duczynski, Z.Chvoj, V.Chab, M.Ondrejcek, H.Conrad: Surface Science, 1995, 331-333, 249-54