Phase transitions of a double occupancy lattice gas

This article offers a detailed analysis of interacting particles in the two-dimensional square array, which is a coarse-graining model to study the multiple occupancy lattice gas system. The equilibrium properties with the maximum loading number 2 is obtained in this work. We find the large nearest neighbor interaction leads to the steeper isotherms and the large on-site interaction leads to the plateaus isotherms. The phase transitions are discussed, and the phase diagrams are obtained via the Monte Carlo simulations. By analyzing finite size effect and the hysteresis behavior, the phase boundaries and the tricritical points are located in the phase diagrams. Our results reveal the complex equilibrium phase transitions in the double occupancy lattice gas.