Diffusion of interacting lattice gases on homogeneous surfaces

Abstract

AbstractTracer and chemical surface diffusion coefficients, D* and D respectively, were studied on a homogeneous surface of square symmetry by means of Monte Carlo modeling. D was determined by the fluctuation autocorrelation function method and from the Kubo‐Green equation. Both techniques yield identical results. Simulations were carried out for a lattice gas model with repulsive nearest neighbor interactions affecting both adsorption sites (ϕNN) and saddle points (ϕ*NN) of the periodic potential. The phase diagram of the lattice gas model shows c(2×2) ordering at low temperatures θ≈︁0.5. It was found that both types of interactions, ϕNN and ϕ*NN, strongly affect surface diffusion. The effects are most pronounced at low tempratures T and high surface coverages θ where the adatoms are closely together. It was found that raising the saddle point energies by ϕ*NN counteracts and may totally compensate for the effect of repulsive nearest neighbor interactions ϕNN.