How good is conformal solutions theory for phase equilibrium predictions?: Gibbs ensemble simulations of binary Lennard-Jones mixtures

Abstract

It is generally believed that conformal solutions theory is valid only for mixtures with components having small differences in energy and size intermolecular potential parameters. To test this assumption, we have used the Gibbs ensemble Monte Carlo simulation technique to calculate phase diagrams of binary Lennard-Jones mixtures obeying the Lorentz—Berthelot combining rules for size parameter ratios equal to 0.5, 1.0 and 1.5 and for energy parameter ratios equal to 0.50, 0.66, 0.75 and 1.00. We generally find good agreement between simulation and theoretical predictions based on an equation of state for the pure Lennard-Jones fluid and the van der Waals one-fluid approximation. Our results establish the validity of conformal solutions theory for simple mixtures of much greater degree of asymmetry than previous investigations.