Nucleation, glass formation, and phase behavior in supercooled liquids

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The liquid state is an enduring source of challenges for our understanding of matter. Even the simplest classical liquid is a dense, disordered, and strongly-interacting many-body system. Liquids thus present us with rich behavior and formidable complexity, especially at the molecular scale. Some of the most important and perplexing open questions in liquid-state physics occur in supercooled liquids. The nature of amorphous solid formation at the glass transition is a continuing source of open debate. Similarly, the nucleation of crystalline solids from the liquid state is also incompletely understood; e.g. the ability of theory to predict crystal nucleation rates with quantitative accuracy remains poor for many important systems. While many of these questions are of a fundamental nature, practical applications abound. For example, the glass-forming ability of metallic alloys is an area of active commercial interest, with new companies making amorphous metal products such as golf clubs and aircraft components. Colloidal liquids are also an area of explosive growth, to which our understanding of classical molecular liquids is directly transferrable. In the context of supercooled liquids, a number of distinct and complex phenomena converge: the thermodynamics of metastable phases; the complex transport properties of viscous liquids; and the non-equilibrium kinetics of crystal nucleation. This proposal describes a program of research to investigate the properties of supercooled liquids, with a deliberate focus on regimes in which these phenomena become intertwined, to better understand all of them. This work will be carried out using molecular dynamics computer simulations, from which both molecular-scale details, as well as estimates of bulk material properties may be obtained.