AN ACCURATE VAN DER WAALS-TYPE EQUATION OF STATE FOR THE LENNARD-JONES FLUID

A new equation of state (EOS) is proposed for the Helmholtz energy F o f the Lennard-Jones fluid which represents the thermodynamic propertie s over a wide range of temperatures and densities. The EOS is written in the form of a generalized van der Waals equation, F=F-H+F-A, where F-H is a hard body contribution and F-A an attractive dispersion force contribution. The expression for F-H is closely related to the hybrid Barker-Henderson pertubation theory. The construction of F-A is accom plished with the Setzmann-Wagner optimization procedure on the basis o f virial coefficients and critically assessed computer simulation data . A comparison with the EOS of Johnson et al. shows improvement in the description of the vapor-liquid coexistence properties, the p upsilon T data, and in peculiar, of the caloric properties. A comparison with the EOS of Kolafa and Nezbeda which appeared after the bulk of this w ork was finished shows still an improvement in the standard deviations of the pressure and internal energy by about 30%.