Triangular Lattice Gas

Abstract

The planar triangular lattice gas with repulsive nearest-neighbor and attractive second-nearest-neighbor interactions is solved in the Bethe-Peierls approximation. The maximum temperature of transition between disordered and ordered phases occurs at a density of one-third. All transitions are first order with a discontinuity in the order parameter at the transition. Deficiencies in the approximation are noted and discussed.