Equation of State for Vapor-Liquid-Solid System

Abstract

Generalizing the idea of order-disorder in the alloy theory, we can calculate the unified equation of state for a lattice gas with many interstitial sublattices in the degree of approximation similar to that developed by Bragg-Williams. For n=9 (n is the number of sublattices), the concrete equation of state is estimated and the ratio of the number of molecules belonging to each sublattice to their total number is given as a function of molecular density. Then the critical temperature and density for vapor-liquid transition are estimated for n=4, 9, 16. Furthermore, it is shown that the density region in the stable liquid phase is very narrow for n=4, but that it becomes wider for n=9, 16.