Soft core thermodynamics from self-consistent hard core fluids

In an effort to generalize the self-consistent Ornstein-Zernike approximation(SCOZA) -- an accurate liquid-state theory that has been restricted so far tohard-core systems -- to arbitrary soft-core systems we study a combination ofSCOZA with a recently developed perturbation theory. The latter was constructedby Ben-Amotz and Stell [J. Phys. Chem. B 108,6877-6882 (2004)] as areformulation of the Week-Chandler-Andersen perturbation theory directly interms of an arbitrary hard-sphere reference system. We investigate the accuracyof the combined approach for the Lennard-Jones fluid by comparison withsimulation data and pure perturbation theory predictions and determine thedependence of the thermodynamic properties and the phase behavior on the choiceof the effective hard-core diameter of the reference system.Comment: 38 pages, 10 figure