New metastable form of ice and its role in the homogeneous crystallization of water.
The homogeneous crystallization of water at low temperature is believed to occur through the direct nucleation of cubic (Ic) and hexagonal (Ih) ices. Here, we provide evidence from molecular simulations that the nucleation of ice proceeds through the formation of a new metastable phase, which we name Ice 0. We find that Ice 0 is structurally similar to the supercooled liquid, and that on growth it gradually converts into a stacking of Ice Ic and Ih. We suggest that this mechanism provides a thermodynamic explanation for the location and pressure dependence of the homogeneous nucleation temperature, and that Ice 0 controls the homogeneous nucleation of low-pressure ices, acting as a precursor to crystallization in accordance with Ostwald's step rule of phases. Our findings show that metastable crystalline phases of water may play roles that have been largely overlooked.
1] Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku Tokyo 153-8505, Japan [2].
John
J
Russo
1] Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku Tokyo 153-8505, Japan [2] Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road Oxford OX1 3QZ, UK [3].
Flavio
F
Romano
Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku Tokyo 153-8505, Japan.
Hajime
H
Tanaka
D003198:Computer Simulation; D003460:Crystallization; D005615:Freezing; D007053:Ice; D008958:Models, Molecular; D009010:Monte Carlo Method; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
D007053:Ice; D014867:Water