Surface tracer diffusion in the presence of a solid barrier: A Monte Carlo study

We investigate, by way of Monte Carlo simulations, the diffusion of adsorbates on a square lattice. The lattice contains inaccessible sites forming linear barriers. The adsorbate atoms do not interact among themselves, except for the hard core. The tracer diffusion coefficients, reduced by their values in the absence of the barrier, are plotted versus the length of the barrier. We find that the diffusion along the barrier is not affected by its presence, whereas that perpendicular to it decreases linearly, for a large interval of the barrier, with its length. The reduced diffusion coefficient does not depend on the concentration of the diffusing particles, but its value increases with the perpendicular distance between the barriers.