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

The latest theoretical developments of crystal nucleation are critically re viewed in two areas: the modeling of the size and temperature dependence of the interfacial free energy and the description of nucleation kinetics. Th e predictions of phenomenological and density functional theories are discu ssed in the knowledge of experiments on oxide glasses. While the advanced m olecular 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 diffu se interface theory were found to reproduce the proper magnitude and sign o f the temperature coefficient for the crystal-liquid interfacial free energ y emerging from nucleation experiments on stoichiometric glasses. The theor y 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.