Monday, 19 June 2006
Eng Ctr Courtyard (University of Colorado at Boulder)

Computer Simulation of Water Crystallization

Yuriy Bushuev, University of Michigan, Ann Arbor, MI

Studying of water crystallization by computer methods is very difficult task because water molecules form irregular three dimensional hydrogen bond networks. The high barrier for phase transition significantly slows down the process of crystallization; the use of molecular dynamic is ineffective for such purpose. We propose two methods of Monte Carlo simulations that give an opportunity to observe and study water nucleation in realistic computational time. The first method is based on using NPT-ensemble with high trial movement and rotation of water molecules. During the simulations with periodic boundary conditions all edge lengths of the elementary cell are changed independently. We used a small cell and TIP5P potential function with short cut off for calculation of interactions. As a result we observed nucleation of several known and unknown crystalline phases, depending on external pressure and temperature. Cubic ice is formed at normal pressure. A free cluster simulation of 5000 molecules shows formation of several cubic ice crystallites. The second method is based on MC simulation with NVT –ensemble. We used small cells with geometrical parameters which were in proportion to parameters of crystallographic cells of ices. We saw crystallization for water models with several potentials. *Permanent address: Ivanovo State University of Chemistry and Technology, Engelsa 7, Ivanovo, Russia

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