THE LENNARD-JONES FLUID - AN ACCURATE ANALYTIC AND THEORETICALLY-BASED EQUATION OF STATE

A new analytic equation of state for the Lennard-Jones fluid is propos ed. The equation is based on a perturbed virial expansion with a theor etically defined temperature-dependent reference hard sphere term. The expansion is written for the Helmholtz free energy which guarantees t he thermodynamic consistency of the pressure and internal energy. The equation covers much wider range of temperatures (up to seven times th e critical temperature) than existing equations and is significantly m ore accurate and has less parameters than the best equation available to date, the modified Benedict-Webb-Rubin equation due to Johnson, Zol lweg, and Gubbins (1993, Mol. Phys. 78: 591-618). As a side-product, h ighly accurate explicit analytic correlations of the hard sphere diame ters, as given by both the hybrid Barker-Henderson and Weeks-Chandler- Andersen theories, have been obtained. Computer simulation data to be regressed by the equation have been compiled from several sources and critically assessed. It has been shown that many literature data for s tate points with a large compressibility are subject to large systemat ic finite-size errors. Additional simulations on a series of systems o f different sizes have been therefore performed to facilitate the extr apolation to the thermodynamic limit in the region close to the critic al point.