A molecular theory of the homogeneous nucleation rate. II. Application to argon vapor

The molecular theory of the homogeneous nucleation rate based on the n/v-Stillinger cluster, and developed in the preceding paper (paper I), is applied to the condensation of supersaturated argon vapor, in a preliminary calculation of the rate of nucleation for a single set of conditions (temperature=85 K, pressure=2500 Torr). Free energies are obtained by means of Monte Carlo simulation. Upper and lower bounds differing by only two orders of magnitude are obtained. Since the best current measurements of vapor phase nucleation rates are accurate to within about a single order of magnitude, this result is considered promising. The direction of future work to improve the accuracy of the predicted rate is clear, and considerable improvement should be possible. These directions are discussed in the paper. Also, the essentially non ad hoc nature of the n/v-Stillinger cluster is demonstrated by the appearance of a range of connectivity distances (in a predicted location) within which the calculated nucleation rate is insensitive to the connectivity distance. As in the case of paper I, subtle features of the nucleation process, unnoticed in earlier theories, are revealed. (C) 1999 American Institute of Physics. [S0021-9606(99)50313-9].