The mechanisms for pressure-induced amorphization of ice I(h)

J. S. Tse, D. D. Klug, C. A. Tulk, I. Swainson, E. C. Svensson, C. K. Loong, V. Shpakov, V. R. Belosludov, R. V. Belosludov, Y. Kawazoe

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There has been considerable interest in the structure of liquid water at-low temperatures and high pressure following the discovery of the high- density amorphous (HDA) phase of ice I(h) (ref. 1). HDA ice forms at a pressure close to the extrapolated melting curve of ice, leading to the suggestion that it may have structure similar to that of dense water. On annealing, HDA ice transforms into a low-density amorphous (LDA) phase with a distinct phase boundary. Extrapolation of thermodynamic data along the HDA- LDA coexistence line into the liquid region has led to the hypothesis that there might exist a second critical point for water and the speculation that liquid water is mixture of two distinct structures with different densities. Here we critically examine this hypothesis. We use quasi-harmonic lattice- dynamics calculations to show that the amorphization mechanism in ice I(h) changes from thermodynamic melting for T > 162 K to mechanical melting at lower temperatures. The vibrational spectra of ice I(h), LDA ice and quenched water also indicate a structure for LDA ice that differs from that of the liquid. These results call into question the validity of there being a thermodynamic connection between the amorphous and liquid phases of water.

Original languageEnglish
Pages (from-to)647-649
Number of pages3
Issue number6745
Publication statusPublished - 1999 Aug 12

ASJC Scopus subject areas

  • General


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