CAREER: Nucleation from solution: a new frontier for molecular simulation

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Baron Peters of the University of California, Santa Barbara is supported by a CAREER award from the Theory, Models and Computational Methods Program in the Chemistry Division to develop molecular simulation strategies for understanding molecular level properties of critical nuclei for nucleation from solution. Nucleation is the process by which the first microscopic embryo of a new phase is formed to initiate a phase transition. Understanding the factors that influence nucleation rates and the features of a nucleus that determine whether it is stable or unstable is a major challenge for experiments and for simulations. The PI uses path sampling, atomistic simulations, lattice models and coarse grained dynamics to understand various aspects of the critical nucleus structure and interfacial energy contributions at the nanoscale. This work extends simulations of nucleation beyond spherical particles and implicit solvents. These efforts combine state-of-the-art methods for rare events with rigorous methods to control the chemical potential (supersaturation) in the condensed phase. Familiar examples of nucleation are the formation of carbon dioxide bubbles in an opened soda or ice crystals in a bottle of water placed in the freezer. Actually these visible droplets, bubbles, or crystals of the new phase are actually later stages in the phase transformation. Microscopic nuclei with just a few molecules may form and re-dissolve many times before finally giving birth to a stable nucleus that can eventually grow to a visible size. In some cases, like the example of bottled water in the freezer, hours or weeks may pass before the first stable nucleus forms. New simulation methods designed specifically for nucleation from solution provide mechanistic insights to guide the crystallization and synthesis of materials with controlled crystal structures, shapes, and properties. The insights gained from this work facilitate the preparation of pharmaceuticals, the synthesis of electronic and catalytic materials, and purification by crystallization..