Density and Diffusion Anomalies in a Repulsive Lattice Gas

We study a purely repulsive lattice gas model. The chemical versus temperature phase diagram is obtained using Grand Canonical Monte Carlo and Wang-Landau algorithms. This system exhibits a gas, two liquid phases and a high temperature fluid phase. In addition to the phase space we also explore this isotropic model for the presence of density and diffusion anomalies. We show that in the vicinity of the critical line between the fluid and the low density liquid phase the system exhibits temperatures of maximum density, minimum density, maximum diffusion and minimum diffusion in a behavior quite similar to the behavior observed in liquid water. Our results indicate that directionality and the presence of attractive interactions are not fundamental for the presence of water-like anomalies. phases.