Dynamics of Equilibrium Liquids, Supercooled Liquids, and Glasses

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Hans Andersen is funded by a grant from the Theoretical and Computational Chemistry Program to continue his studies of the dynamics and equilibrium of liquids, supercooled liquids and glasses. Andersen will develop and use three types of statistical mechanical methods for the study of the kinetic theory of dense supercooled fluids: 1) a formulation of the Martin, Siggia, Rose (MSR) approach applied to the classical dynamics of particle and spin systems; 2) molecular dynamics simulation studies of dense, low temperature and slightly supercooled atomic liquids; and 3) simulation of the time dependence of kinetic spin models designed to elucidate mechanisms for relaxation and structural change in highly supercooled liquids and glasses. The major objectives of the research are: 1) to provide critical tests of the derivation and accuracy of the extended mode coupling theory and a greater understanding of the physical content of the theory; 2) to develop a basis for kinetic theory that is an alternative to the use of projection operators or the four-point function of Mazenko; and 3) to understand how to incorporate such phenomena as formation of frustration-limited domains, secondary relaxation, and inhomogeneous relaxation into kinetic theory. Molecular dynamics simulations will be used to study liquids and slightly supercooled regimes, and more schematic spin models will be used at lower temperatures where the relevant time scales are longer. Glasses are technologically important materials made from a variety of components, both organic and inorganic, both small molecular weight substances and polymers. Examples include ordinary materials such as window glass and food containers, as well as high-tech materials for telecommunications, optoelectronics, and solid electrolytes. As nonequilibrium materials, their properties depend on how they are made, which usually involves preparation of a high temperature liquid followed by various cooling and processing steps. The preparation of such materials to achieve optimal performance is guided largely by empirical observations, but Andersen's research seeks an understanding of the dynamics of these materials and their corresponding liquids on a molecular level which can be useful in the design of rational processing procedures.