A MONTE-CARLO STUDY OF SURFACE-DIFFUSION COEFFICIENTS IN THE PRESENCE OF ADSORBATE ADSORBATE INTERACTIONS .1. REPULSIVE INTERACTIONS

Chemical, jump, and tracer diffusion coefficients, D, D(j), and D*, respectively, for the case of nearest-neighbor repulsive interactions have been determined by Monte Carlo simulations on a fixed square lattice. D was determined by the fluctuation autocorrelation function method and from the Kubo-Green equation, using values of <(delta-N)2>/<N> determined from isotherms. It was found that the two methods give essential agreement over the entire coverage and temperature range examined, 0.73 less-than-or-equal-to T/T(c) less-than-or-equal-to 7.33, 0.1 less-than-or-equal-to theta less-than-or-equal-to 0.8. The changes in activation energies for D, D*, and D(j) as function of T and theta were determined and can be understood in terms of the phase diagram of the system.