Vapour-liquid critical lines predicted by distribution function theories

Abstract

The structure of binary fluid mixtures has been studied using the Ornstein-Zernike equation in the Percus-Yevick (P-Y) approximation. Through the Kirkwood-Buff formalism, the mixture spinodal curves and critical loci have been determined. Results for systems with various interaction parameters are presented to demonstrate the influence of differences in molecular size and attractive interactions upon the critical locus. The predictions of the P-Y theory are compared with those of the van der Waal's one-fluid (vdW-1) theory as well as recent estimates from Monte Carlo computer simulations. Quite good agreement with the computer simulation results for the critical locus is obtained. The P-Y and vdW-1 theories predict the same qualitative behaviour for each of the systems studied.