Surface diffusion in a system of particles adsorbed on a two-dimensional strongly anisotropic lattice was investigated. There were two kinds of the lattice sites – ordinary sites and deep traps. Particles adsorbed in the ordinary sites could migrate over the surface, but particles adsorbed in traps were immobile. These particles did not move over the surface and they obstacle also the mobile particles migration (surface defects). Using kinetic Monte Carlo simulations, coverage dependences of the tracer, jump, and chemical diffusion coefficients were obtained. The coefficients were rather sensitive to the defect concentration. Even small admixture of the defects decreased drastically the fast diffusion. The effect was rather specific: strong dependence of the pre-exponential factor upon the defect concentration and almost independent activation energy. The defect influence upon the slow diffusion was weak. It resulted in strong decreasing of the surface diffusion anisotropy with the defect concentration. Such unusual behavior of the diffusion coefficients was observed in many experimental investigations of the surface diffusion of lithium, cesium, potassium, and strontium over strongly anisotropic W(112) and Mo(112) planes. It was shown that this specific behavior arose exclusively due to the surface anisotropy, and did not depend upon the lateral interaction between the particles.

Diffusion of Particles over Strongly Anisotropic Surface with Traps. A.Tarasenko, L.Jastrabik: Surface Science, 2009, 603[3], 529-36