Molecular dynamics simulations of ice growth from supercooled water

Abstract

The kinetics of ice growth on the secondary prismatic plane

and the basal plane {0001} is studied by Molecular Dynamics simulations. The simulation system initially consists of a slab of ice in contact with a layer of water on one side, and vacuum on the other side. The remaining surface of the water layer is also facing vacuum. The time evolution of the system shows the crystallization of the liquid water and the evaporation of very few molecules at the free surfaces. The ice vapour interfaces are wet on both sides by identical thin layers of liquid water, strongly suggesting that the system has reached its equilibrium state. To analyse the results, we have developed a new method to discriminate whether a molecule belongs to the ice lattice or is in liquid state. Using this method to monitor the number of ice molecules as a function of time, we find that the freezing is much faster on the prismatic plane than on the basal plane. For the prismatic plane, irregularities in the surface of the solid phase are observed during the growing period contrasting with a smooth interface on the basal plane at all times. We studied three different temperatures and found that the rate of crystallization decreases with temperature for the prismatic plane, while no conclusive behaviour was found for the basal plane growth.

Keywords:

• Molecular dynamics simulations
• Ice growth
• Supercooled water

Acknowledgements

It is a pleasure to dedicate this work to Professor Ben Widom whose immense wisdom, patience and teachings has inspired our work throughout the years. This work is partially supported by the National Science Foundation. We would like to thank Prof. Hiroki Nada for providing us with ice configurations and energy values during the initial stages of this work.