Nonclassical nucleation theory

Abstract

Gibbs's theory of the formation of nuclei in the metastable phase of a two-phase system was reformulated by Cahn and Hilliard in order to eliminate Gibbs's condition that the nucleus be homogeneous up to a sharp boundary with the outside phase. This paper extends the Cahn-Hilliard theory of nucleation to systems having nonclassical Helmholtz free energies. The results of this study show that nucleation in the metastable region follows a completely different pattern than that predicted by Cahn and Hilliard. Most important is the extension of the range of stability of a fluid system close to its critical point. This is in contrast to the Cahn-Hilliard theory in which the region of stability becomes smaller and disappears as the critical point is approached. Recent experimental results of Huang, Vernon, and Wong give good agreement with our theory.