Two-dimensional bonded lattice fluids I. Interstitial model

Abstract

The density, pressure and temperature state surface is studied for a 'bonded' fluid on a plane triangular lattice. Calculations were made using a first-order statistical approximation based on a triangular group of sites. Separation between liquid and vapour phases occurs below a critical pressure pc. If the interaction energy of an unbonded nearest-neighbour pair of molecules is zero the properties of the model can be related to those of an Ising ferromagnet on a honeycomb sublattice and accurate values deduced for the critical density, pressure and temperature.