Variational theory of phase separation in binary liquid mixtures

Abstract

It is shown that a double Yukawa potential provides a good physical representation for pair potentials in molecular fluids and that its use greatly simplifies variational calculations based on the Percus–Yevick hard-sphere reference system. The calculations show that for this reference fluid the virial hard-sphere equation of state is preferred to the semiempirical Carnahan–Starling expression. The variational procedure is used to calculate the fluid phase diagrams for two binary noble-gas mixtures.