Diffusion in a two-dimensional periodic potential

We report a numerical study of the self-diffusion of a single-point particle in a two-dimensional periodic potential of triangular symmetry. The self-diffusion coefficient is obtained via computer simulations for several values of the particle energy. We find that the self-diffusion process is complicated due to the existence of correlated motions involving two or more cells. A random-walk model which takes into account the effects of correlated motions involving only the nearest-neighbor cells is constructed, and compared with the experimental results.