A new theory of simple classical fluids

The paper presents a unified structural and thermodynamic theory of simple classical fluids in which the interactions between the particles can be represented by spherically symmetric pairwise potentials. Both the excess entropy and the gross features of the radial distribution function are determined mainly by excluded volume effects, which are in turn governed by a hard-core property intrinsic to any pair potential. The potential beyond this effective hard core is considered relatively weak and can be treated as a perturbation. It is also considered essential to sum all subclasses of diagrams to infinite order. The basic form of a diagrammatic scheme which allows both summation and the determination of the structure and excess entropy is presented, and a statement of universality is derived. The statement has been confirmed within the accuracy of present-day computer simulations, and a possible procedure for calculating both the structure and thermodynamics of every physically conceivable pair potential is presented.