Surface diffusion of particles adsorbed on a lattice with two non-equivalent sites

We investigate the surface diffusion in a system of particles adsorbed on a lattice with two non-equivalent sites, whose number in the unit cell and adsorption energy are different. When the adsorption energies are comparable, the adparticle diffusion proceeds by uncorrelated adparticle jumps. In the opposite case, the adparticle migration proceeds by pairs of consecutive jumps. The contributions to the surface diffusion of these jump sequences depend considerably on the adparticle surface coverage and the relation between the adsorption energies.