Lattice-gas model of diffusion of NH3 on Re(0001)

A lattice-gas model for the chemical diffusion of NH3 on Re(0001) is presented. The system is modelled as a triangular lattice gas with nearest-neighbour repulsive lateral interactions. The average jump rate and the static structure factor are calculated within the cluster variation method framework by using a cluster of seven sites. Then the chemical diffusion coefficient is evaluated in the Darken approximation. This results in the jump rate and diffusion coefficient strongly increasing with coverage in agreement with experimental measurements.