Emendations to Nucleation Theory and the Homogeneous Nucleation of Water from the Vapor

Abstract

Recent developments in nucleation theory have vitiated the agreement that was thought to exist between experiments and theory on the condensation of water vapor. The various developments are critically reviewed. The thermodynamic terms in nucleation theory are derived in a more comprehensive manner than heretofore. Arguments are presented to show that the alleged positional entropy contribution to the surface-free energy does not exist. The final expression for homogeneous nucleation rate, without, however, any correction for the effect of surface curvature on surface-free energy, is evaluated. The Kirkwood—Buff equation for the effect of curvature is shown to lead to an impossible situation. A bond-breaking model is developed and used to estimate an upper limit for the correction of the surface-free energy for curvature. It is found that the experimental results for the condensation of water vapor are largely bracketed by the nucleation theory with and without the correction for curvature. It is concluded that the amended classical theory of nucleation is reasonably well verified by experiments on condensation of water vapor.