Statistical Mechanics of Condensing Systems. III

TLDR

The Gibbs phase integral is generalized for chemically saturated molecules, yielding equations for their thermodynamic properties. The derived equations predict gas condensation into a condensed phase with surface tension below a characteristic temperature Tm, zero surface tension at Tm with a discontinuous transition without heat, a finite volume interval of constant pressure and Gibbs free energy between Tm and the critical temperature Tc, and above Tc a conventional P–V diagram with no volume where (∂P/∂V)T = 0.

Abstract

A general development of the Gibbs phase integral for a system of chemically saturated molecules gives equations for the thermodynamic properties of the system. The equations predict the usual condensation phenomenon of the gas to form a condensed phase with a surface tension at temperatures below a characteristic temperature Tm. At Tm the surface tension of the condensed phase is zero, and this phase undergoes a discontinuous change without heat of transition. Between Tm and the true critical temperature Tc, there exists a finite volume interval for which P and the Gibbs free energy F is independent of the volume. Above Tc the usual P—V diagram predicted above the critical point is found, with no volume for which (∂P/∂V)T is zero.