On the theory of surface diffusion: kinetic versus lattice gas approach

The present paper extends the results of a recent analytic kinetic theory o f particle-on-substrate diffusion. The approach treats explicitly the molec ule-surface interaction and takes into account inter-molecular interaction within the hard particle approximation. The physics influencing the diffusi on pre-exponential factor and mechanisms determining the density dependence of collective diffusivity are discussed. The kinetic results are compared with those of the traditional lattice gas hopping models. Analytical expres sions for jump rates in the low density limit are derived, and the density dependence of effective jump rates at finite occupancy is discussed. It is shown how the traditional hopping model oversimplifies the picture of diffu sion by neglecting the collision part of the hopping process. (C) 1999 Else vier Science B.V. All rights reserved.