ChBE Seminar Series: Valeria Molinero
Tuesday, February 28, 2012
11:00 a.m.-12:00 p.m.
Room 2110 Chemical and Nuclear Engineering Bldg.
Professor Panagiotis Dimitrakopoulos
Crystallization of Water: From the Bulk to the Nanoscale
Physical and Materials Chemistry
Department of Chemistry
University of Utah
One of waters unsolved puzzles is the question of what determines the lowest temperature to which it can be cooled before freezing to ice. The supercooled liquid has been probed experimentally to near the homogeneous nucleation temperature, TH = 232 K, yet the mechanism of ice crystallizationincluding the size and structure of critical nucleihas not yet been resolved. The heat capacity and compressibility of liquid water anomalously increase on moving into the supercooled region, according to power laws that would diverge at 225 K so there may be a link between waters thermodynamic anomalies and the crystallization rate of ice. But probing this link is challenging because fast crystallization prevents experimental studies of the liquid below TH. And although atomistic studies have captured water crystallization3, high computational costs have so far prevented an assessment of the rates and mechanism involved. To address this issue, we developed an efficient and surprisingly accurate coarse-grained model of water, the monatomic water model mW, that represents water as an element of tetrahedrality intermediate between carbon and silicon. Using the mW water model we investigated the relationship between structure of liquid water, the thermodynamic anomalies of the liquid and the rate of crystallization of ice, and elucidated the structure of ice formed from deeply supercooled water.