Simulation of the diffusion of atoms in a dense adsorbed layer with a hexagonal structure

Abstract

Molecular dynamics methods are used to study the kinetics of the migration of impurity atoms due to the diffusion of vacancies on a honeycomb-type lattice. A particular attention is paid to examining how the impurity diffusion coefficient depends on the coverage of vacancies ϑ_v. It is shown that, in the limit of vanishingly small concentration of vacancies, ϑ_v ≪ 1, this dependence is linear, with the simulation results being consistent with the predictions of our analytical theory. With increasing ϑ_v, the diffusion coefficient begins to grow nonlinearly, correlating with the increase in the size of the percolation clusters. Above the percolation threshold, the impurity diffusion coefficient tends rapidly to its value for a surface without obstacles.