Kinetic boundaries and phase transformations of ice i at high pressure.
Kinetic boundaries and phase transformations of ice i at high pressure.
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DOI：
10.1063/1.5017507
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发表时间：
2018-01
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影响因子：
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通讯作者：
Yu Wang;Huichao Zhang;Xue Yang;Shu-qing Jiang;A. Goncharov
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文献类型：
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作者：
Yu Wang;Huichao Zhang;Xue Yang;Shu-qing Jiang;A. Goncharov
利用金刚石砧细胞中的拉曼光谱研究了高压至16 GPa、低温至15 K条件下H2O冰的相界和转变动力学。在液态水接近等压冷却时形成的冰i，在15-100 K的温度下，在1.1-3 GPa的温度下转变为高密度无定形冰（HDA），然后在冰vii中结晶，在80 K和100 K的温度下，冰vii保持稳定在14.1 GPa和15.9 GPa。出乎意料的是，在冰vii'的减压过程中，它在亚稳域中转变为冰viii，然后在随后的压力释放和升温过程中松弛成低密度无定形（LDA）冰。冰i在150 ~ 170 K压缩时，冰i结晶，未发现HDA冰；冰ix进一步压缩导致连续相变到稳定的冰vi和冰viii。将冰i在0.3 GPa下冷却至210 K，使其转变为稳定的冰ii。我们广泛的调查提供了以前缺少的关于水的相图的信息，特别是在导致相形成的动力学路径上，否则是无法获得的；这些结果是理解包括亚稳相形成在内的相关系的关键。我们的观测告诉我们，冰的变化可能在行星环境中自然发生，而且无法进行直接观测。
Raman spectroscopy in diamond anvil cells has been employed to study phase boundaries and transformation kinetics of H2O ice at high pressures up to 16 GPa and temperatures down to 15 K. Ice i formed at nearly isobaric cooling of liquid water transforms on compression to high-density amorphous (HDA) ice at 1.1-3 GPa at 15-100 K and then crystallizes in ice vii with the frozen-in disorder (ice vii') which remains stable up to 14.1 GPa at 80 K and 15.9 GPa at 100 K. Unexpectedly, on decompression of ice vii', it transforms to ice viii in its domain of metastability, and then it relaxes into low-density amorphous (LDA) ice on a subsequent pressure release and warming up. On compression of ice i at 150-170 K, ice ix is crystallized and no HDA ice is found; further compression of ice ix results in the sequential phase transitions to stable ices vi and viii. Cooling ice i to 210 K at 0.3 GPa transforms it to a stable ice ii. Our extensive investigations provide previously missing information on the phase diagram of water, especially on the kinetic paths that result in formation of phases which otherwise are not accessible; these results are keys for understanding the phase relations including the formation of metastable phases. Our observations inform on the ice modifications that can occur naturally in planetary environments and are not accessible for direct observations.