TRACER DIFFUSION OF PARTICLES WITH SOFT-CORE INTERACTIONS STUDIED BY MONTE-CARLO SIMULATIONS

We consider, using Monte Carlo simulations, diffusion of particles on a square lattice. The particles do not interact among themselves, exce pt that at the same lattice site there cannot be more than N particles . Since the interactions in our model are a milder version of the well known hard-core (HC) lattice gas, for which N = 1, we decided to call our model the soft-core (SC) lattice gas. We find the dependence of t he correlation factor on the concentration of completely filled sites and show that the correlations decrease with increasing N. We calculat e analytically and via the Monte Carlo simulations the distribution fu nction of the average number of sites occupied by a given number of pa rticles. The curves show that for our model the 'particle-hole' symmet ry, typical for the HC lattice gas, disappears. In addition, we have f ound in 1D two regimes of diffusion for N = 2. For shorter times the d iffusion is anomalous, while for longer times it becomes normal.