Monte Carlo results were presented for the Haven ratio in the square planar lattice gas with nearest-neighbor exclusion and the square planar lattice gas with nearest-neighbor repulsion and next-nearest neighbor attraction with the latter at a temperature less than the critical temperature at 50% occupation. Unlike the simple cubic athermal lattice gas studied earlier, a minimum in the ratio occurred at concentrations less than the critical concentration because of a percolation requirement. The lattice gas with finite interactions exhibited turning points at the phase transitions with apparent accompanying changes in the percolation behavior and diffusion mechanism.

Computer-Simulation Study of the Behaviour of the Haven Ratio Near Order/Disorder Transitions in Highly Defective Solids. G.E.Murch: Philosophical Magazine A, 1981, 44[3], 699-709