A kinetic theory of nucleation in liquids

Abstract

A kinetic theory of nucelation is developed in which the rate of dissociation of the nuclei is calculated on the basis of a mean first passage time analysis. In contrast to the classical theory of nucleation, the theory does not employ the macroscopic concept of interfacial tension and the principle of detailed balance. It involves, instead, the interaction between a molecule and a cluster. An equation is derived for the critical radius, which in the limit of large clusters yields the Kelvin equation as well as an expression for the macroscopic surface tension. Numerical calculations assuming an interaction potential between two molecules which combines the dispersive attraction with the rigid core repulsion are performed. The predictions of the theory are consistent with the classical results in the limit of large critical clusters, i.e., for small supersaturations. For small critical clusters the present theory provides much higher rates of nucleation than the classical one. This difference can be attributed to the fact that the classical theory uses the macroscopic interfacial tension, which overpredices the surface energy of small clusters, and consequently provides lower values for the nucelation rate. The present paper extends the approach initiated in the previous paper ( G. Narsimhan and E. Ruckenstein, J. Colloid Interface Sci. 128, 549, 1989 ) to a more realistic interaction potential.