FREE-ENERGY IN THE STATISTICAL-THEORY OF FLUIDS

Explicit formulas for the excess chemical potential and Helmholtz free energy have been derived in different ways making use of a functional integration technique. The method employed is an extension of the Kirkwood "charging" procedure and involves a new way of renormalizing cluster series. The formulas require only the correlation functions for the system under investigation. New and old ways of calculating the free energy of a simple fluid are compared and discussed. Numerical results for the various closures are presented for hard and Lennard-Jones sphere fluids. A bridge functional of the first kind has been introduced and some approximations for this have been proposed and tested. © 1990 American Institute of Physics.