title: Multiple phase transitions in extended hard-core lattice gas models in two dimensions.
abstract: We study the k-NN hard-core lattice gas model in which the first k next-nearest-neighbor sites of a particle are excluded from occupation by other particles on a two-dimensional square lattice. This model is the lattice version of the hard-disk system with increasing k corresponding to decreasing lattice spacing. While the hard-disk system is known to undergo a two-step freezing process with increasing density, the lattice model has been known to show only one transition. Here, based on Monte Carlo simulations and high-density expansions of the free energy and density, we argue that for k = 4,10,11,14,⋯, the lattice model undergoes multiple transitions with increasing density. Using Monte Carlo simulations, we confirm the same for k = 4,...,11. This, in turn, resolves an existing puzzle as to why the 4-NN model has a continuous transition against the expectation of a first-order transition.
authors.affiliation: The Institute of Mathematical Sciences, C.I.T. Campus, Taramani, Chennai 600113, India.
authors.forename: Trisha
authors.initials: T
authors.lastname: Nath
authors.affiliation: The Institute of Mathematical Sciences, C.I.T. Campus, Taramani, Chennai 600113, India.
authors.forename: R
authors.initials: R
authors.lastname: Rajesh
mesh_terms: D005740:Gases / Q000737:chemistry*; D008958:Models, Molecular; D009010:Monte Carlo Method; D044367:Phase Transition
chemical_list: D005740:Gases