Connection between thermodynamic properties and diffusion coefficient for a system of non-interacting particles on a lattice with two non-equivalent sites

By calculating the jump diffusion rate (T) and the thermodynamical factor (K-d) for a layer of non-interacting particles on a lattice with the non-equivalent bond sites we show that the diffusion coefficient D = Gamma K-d exhibits specific features as a function of coverage, such as steps or maxima at critical coverages, which correspond to phase transformations in the adlayer. The chemical potential of the adlayer is derived analytically from the free energy. The difference of binding energy between the two kinds of sites is described by a parameter k and it is shown that the chemical potential (or the thermodynamic factor) at the critical coverage indicates the existence of a diffuse phase transition which develops for k --> 0 into a first-order point phase transition.