Self-diffusion of protons in H2O ice VII at high pressures: Anomaly around 10 GPa
Self-diffusion of protons in H2O ice VII at high pressures: Anomaly around 10 GPa
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DOI：
10.1063/1.4953688
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发表时间：
2016-06-21
影响因子：
4.4
通讯作者：
Okuchi, Takuo
中科院分区：
文献类型：
--
作者：
Noguchi, Naoki;Okuchi, Takuo
使用显微拉曼光谱和金刚石砧池研究了冰 VII 在 5.5-17 GPa 的压力范围和 400-425 K 的温度范围内的自扩散。通过观察同位素示踪剂：D2O 和 (H2O)-O-18 的分布来监测扩散。氢的扩散系数在10 GPa左右达到最大值。 10 GPa 时比 6 GPa 时高两个数量级。氢扩散比氧扩散快得多，这表明质子扩散是氢在冰VII中扩散的主要机制。这种机制与冰 I-h 中的自扩散形成鲜明对比，后者由整个水分子的间隙机制主导。质子电导率测量和分子动力学模拟表明，冰 VII 中 10 GPa 左右的异常表明质子扩散的速率决定过程从离子缺陷扩散转变为旋转缺陷扩散。由 AIP 出版社出版。
The self-diffusion of ice VII in the pressure range of 5.5-17 GPa and temperature range of 400-425 K was studied using micro Raman spectroscopy and a diamond anvil cell. The diffusion was monitored by observing the distribution of isotope tracers: D2O and (H2O)-O-18. The diffusion coefficient of hydrogen reached a maximum value around 10 GPa. It was two orders of magnitude greater at 10 GPa than at 6 GPa. Hydrogen diffusion was much faster than oxygen diffusion, which indicates that protonic diffusion is the dominant mechanism for the diffusion of hydrogen in ice VII. This mechanism is in remarkable contrast to the self-diffusion in ice I-h that is dominated by an interstitial mechanism for the whole water molecule. An anomaly around 10 GPa in ice VII indicates that the rate-determining process for the proton diffusion changes from the diffusion of ionic defects to the diffusion of rotational defects, which was suggested by proton conductivity measurements and molecular dynamics simulations. Published by AIP Publishing.