Weakly first-order transition in an athermal lattice gas

We investigate the phase behavior of a two-dimensional athermal lattice gas in which every hard-core particle can have two or fewer nearest neighboring occupied sites on the square lattice. The ground state and close packing density are determined and it is found that at large chemical potential the model undergoes an ordering phase transition with preferential sublattice occupation. Although near the transition point the particle density and entropy exhibit an apparent discontinuity, we find that the order parameter and fluctuations of thermodynamic quantities do not scale with the system volume. These paradoxical results are reconciled by analyzing the size-dependent flow of the thermal exponent by phenomenological renormalization and the curve-crossing method, which lead to a weakly first-order phase transition scenario.

Automated summary

We investigate the phase behavior of a two-dimensional athermal lattice gas and find that it undergoes an ordering phase transition with preferential sublattice occupation at large chemical potential. Although there is an apparent discontinuity in particle density and entropy near the transition point, the order parameter and fluctuations of thermodynamic quantities do not scale with the system volume.