A reference hypernetted-chain equation for soft potentials. Atomic and molecular Lennard-Jones systems

A recently proposed reference hypernetted-chain equation based on a semiphenomenological bridge function due to Verlet is reformulated for atomic and molecular Lennard-Jones liquids. In this new approximation we treat the size of the reference-system hard particles as a function of density and temperature through a functional relationship presented herein. The theory yields excellent results for the structure and thermodynamics of atomic Lennard-Jones liquids over a wide range of temperature and density and is quite satisfactory for Lennard-Jones homonuclear diatomics.