A ONE-DIMENSIONAL DESCRIPTION OF SURFACE-DIFFUSION FOR ADLAYERS WITH LATERAL INTERACTIONS

An analytical expression for the surface diffusion coefficient is derived by summing the fluxes due to single jump events between adjacent sites on a simple square lattice. All microscopic configurations of a layer of interacting particles are included at particular coverages. In a quasi-chemical approach, the nearest-neighbour particle-particle interactions are introduced by adjusting the jump rate as well as by adapting the probability of occurrence of particular configurations consistent with the concentration. The diffusion coefficient is found to be dominated by the latter contribution at medium and high concentrations. A comparison with the results of Monte Carte simulations shows that an improved approximation can be achieved if the interactions are accounted for not only by changes of the activation energy of diffusion but also by their effect on the equilibrium distribution of the particles.