INFLUENCE OF 3-BODY FORCES ON THE GAS-LIQUID COEXISTENCE OF SIMPLE FLUIDS - THE PHASE-EQUILIBRIUM OF ARGON

The effect of three-body classical dispersion forces on the gas-liquid coexistence of argon is explored by means of a reference hypernetted- chain integral equation and Gibbs ensemble Monte Carlo simulations. We find that the combination of Aziz's [J. Chem. Phys. 99, 4518 (1993)] pair interaction with the standard Axilrod-Teller [J. Chem. Phys. 11, 299 (1943)] triple dipole potential leads to the best prediction of th e experimental coexistence curve. By contrast, when the Lennard-Jones potential is used in conjunction with the Axilrod-Teller interaction t he calculated curve deviates appreciably from the experimental data, f ar from improving the reasonable plain Lennard-Jones results. Addition ally, the integral equation approach with an effective state-dependent pair potential to account for the three-body interactions leads to ve ry accurate results for the thermodynamic and coexistence properties o f the fluid. This feature comes to prove that the theory can be an inv aluable tool for studying systems with three-body interactions of the Axilrod-Teller type.