Non-classical theory of crystal nucleation:: application to oxide glasses:: review

The latest theoretical developments of crystal nucleation are critically reviewed in two areas: the modeling of the size and temperature dependence of the interfacial free energy and the description of nucleation kinetics. The predictions of phenomenological and density functional theories are discussed in the knowledge of experiments on oxide glasses. While the advanced molecular approaches based on the density functional theory provide detailed microscopic information on nucleation in simple model systems, they appear to have limited relevance to such complex systems as the oxide glasses. In contrast, a semiempirical Cahn-Hilliard model and a phenomenological diffuse interface theory were found to reproduce the proper magnitude and sign of the temperature coefficient for the crystal-liquid interfacial free energy emerging from nucleation experiments on stoichiometric glasses. The theory of nucleation kinetics has made many advances in recent years. Analytical and numerical methods are available now for the evaluation of experiments, including such effects as dissolution of athermal nuclei in two-step heat treatments. (C) 1999 Elsevier Science B.V. All rights reserved.