Analysis of the Arrhenius shape of the diffusion coefficient on an fcc (111) surface

We study the temperature and coverage dependence of an effective diffusion barrier assuming an Arrhenius shape of the chemical diffusion coefficient f or a system of interacting particles. The previously published model of the diffusion of an fee (111) surface with bivariate trap is used. The presenc e of two nonequivalent occupation sites and interaction result in a non-Arr henius shape of the diffusion coefficient and a coverage- and temperature-d ependent effective diffusion barrier. The temperature dependence of effecti ve energy E-a shows a minimum at low temperatures (at approximately 150 K) for strong interactions. The coverage dependence of E-a has a deep minimum in the vicinity of Theta = 1/2, even in a system without interaction.