ALTERNATIVE DERIVATION OF WIDOMS TEST PARTICLE INSERTION METHOD USINGTHE SMALL SYSTEM GRAND-CANONICAL ENSEMBLE

By using the small system grand canonical ensemble of Soto-Campos, G., Corti, D. S., and Reiss, H., 1998, J. chem. Phys., in press, an alter native derivation is presented of the test particle insertion method f or calculating the excess chemical potential of a system of interactin g particles. By letting an arbitrarily placed open region within the f luid approach zero volume, the chemical potential is shown to be given by the particle insertion method. The potential benefits of the small system ensemble in obtaining accurate estimates of the chemical poten tial for dense systems are discussed.