Prediction of Water Crystallization from The Microscopic Structure of The Liquid.
The state of water-liquid, ice, or glass - determines the physical properties and chemical stability of materials, the absorption of solar energy by the atmosphere and the survival of organisms in cryogenic conditions. Water does not necessarily freeze at its equilibrium melting point, because the formation of crystals is a kinetically activated process. Nucleation of ice in pristine water is not observed until -34⁰C, and it is known that pressure, solutes and confining interfaces all affect the freezing temperature of water. One of water's unsolved puzzles is what determines the lowest temperature at which the liquid can be equilibrated before freezing to ice, and whether it will form ice at all or an amorphous solid, a glass. I hypothesize that a change in liquid structure, driven by a high- to low- density transformation in supercooled water controls the process of ice nucleation. In this project we will use molecular simulations to characterize the microscopic mechanisms of ice nucleation, thermodynamics, rate of ice crystallization, and the structure of liquid and ice, with the goal of developing a microscopic theory that predicts nonequilibrium freezing temperatures from the equilibrium structure of supercooled liquid water in the system. The systems to be studied comprise bulk and confined water and solutions. We will assess the validity of the proposed methodology for systems that present heterogeneous ice nucleation and the universality in the relationship between freezing rates and liquid structure in the case of mixtures.
Arnold O. Beckman exemplifies the meaning of the word humanitarian. Combined with his unwavering enthusiasm for life, his keen sense of humor and his strong moral and ethical principles, he is a national icon.