Thermodynamic properties of high-density fluids

Abstract

In the calculations of the thermodynamic properties of a fluid near its freezing point, we use the theory of Weeks, Chandler, and Anderson with the modification of breakpoint of an intermolecular potential. The nearest neighbor distance of a face-centered cubic lattice is used as the breakpoint. The calculations are made for a Lennard-Jones system, an inverse 12th-power system, and a system whose particles obey an exponential-six potential. The result shows a good agreement with exact Monte Carlo data. By making the perturbation potential smoother at breakpoint, we can obtain the high-density equilibrium properties of a fluid which come more closely to the exact Monte Carlo data. The radial distribution function for the inverse 12th-power system at $T^{\ast}=100$ and $\rho^{\ast}=2.5$ is obtained by the perturbation theory using our modification. This is compared with the Monte Carlo data and the radial distribution function of the Weeks, Chandler, and Anderson theory.