Growing correlation length in supercooled water

EB Moore and V Molinero, JOURNAL OF CHEMICAL PHYSICS, 130, 244505 (2009).

DOI: 10.1063/1.3158470

The evolution of the structure of water from the stable high temperature liquid to its glass, low-density amorphous ice (LDA), is studied through large-scale molecular dynamics simulations with the mW model J. Phys. Chem. B 113, 4008 (2009). We characterize the density, translational, and orientational ordering of liquid water from the high temperature stable liquid to the low-density glass LDA at the critical cooling rate for vitrification. A continuous transition to a tetrahedrally ordered low-density liquid is observed at 50 K below the temperature of maximum density and 25 K above a temperature of minimum density. The structures of the low-density liquid and glass are consistent with that of a continuous random tetrahedral network. The liquid-liquid transformation temperature T(LL), defined by the maximum isobaric expansivity, coincides with the maximum rate of change in the local structure of water. Long-range structural fluctuations of patches of four-coordinated molecules form in the liquid. The correlation length of the four- coordinated patches in the liquid increases according to a power law in the range 300 K to T(LL) + 10 K; a maximum is predicted at T(LL). To the best of our knowledge this is the first direct estimation of the Widom line of supercooled water through the analysis of structural correlations. (C) 2009 American Institute of Physics. DOI: 10.1063/1.3158470

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