Theoretical Studies of the Liquid State

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Professor David Oxtoby, University of Chicago, is supported by a grant from the Theoretical and Computational Chemistry Program to continue his research in theoretical studies of nucleation. Oxtoby uses techniques of statistical mechanics, specifically density functional methods, to explore phase changes involving liquids: the condensation of liquids from the vapor and the crystallization of liquids to form solids. The rates of these phase changes depend critically on the process of nucleation, the first appearance of a new phase at the center of an existing metastable phase. Oxtoby's work seeks to apply new theoretical approaches to predict the rates of formation and the atomic structures of the critical nuclei that from the barrier to the formation of new phases. The theoretical approaches being developed by Oxtoby will be applicable to both the nucleation of liquids from gases and the nucleation of crystalline solids from liquids. A familiar example of nucleation of liquids from gases is the condensation of water vapor in clouds. There is considerable current interest in the formation of polar stratospheric clouds, which are thought to play a key role in the depletion of ozone over the poles. In all such processes, the first barrier which must be surmounted is the formation of critical nuclei on which other molecules then condense. Oxtoby's research will lead to a theoretical molecular level interpretation of the nucleation event in such systems.