Collective diffusion on hexagonal lattices - repulsive interactions

Diffusion of interacting particle on a hexagonal lattice is studied by use of Monte Carlo simulations for a range of densities and temperatures includ ing ordered and disordered phases. The decay of the initially prepared dens ity perturbation is analyzed. Fast, local ordering happens at the beginning of system relaxation and clearly separates as a function of time the much slower global diffusion process. Locally equilibrated density perturbation decays according to the macroscopic diffusion equation, which allows a coll ective diffusion coefficient to be calculated. The density dependence of th e collective diffusion coefficient is shown for several temperatures above and below the critical temperature. (C) 1999 Elsevier Science B.V. All righ ts reserved.