Thermodynamic properties and homogeneous nucleation rates for surface-melted physical clusters

Abstract

We predict the free energy of van der Waals clusters (Fn) in the surface-melted temperature regime. These free energies are used to predict the bulk chemical potential, surface tension, Tolman length, and vapor pressure of noble gas crystals. Together, these estimates allow us to make definitive tests of the capillarity approximation in classical homogeneous nucleation theory. We find that the capillarity approximation underestimates the nucleation rate by thirty orders of magnitude for argon. The best available experiments are consistent with our calculation of nucleation rate as a function of temperature and pressure. We suggest experimental conditions appropriate for determining quantitative nucleation rates which would be invaluable in guiding further development of the theory. To make the predictions of Fn, we develop the Shellwise Lattice Search (SLS) algorithm to identify isomer fragments and the Linear Group Contribution (LGC) method to estimate the energy of isomers composed of those fragments. Together, SLS/LGC approximates the distribution of isomers which contribute to the configurational partition function (for up to 147-atom clusters). Estimates of the remaining free energy contributions come from a previous paper in this series.