Pressure-induced dissociation of water molecules in ice VII.
Pressure-induced dissociation of water molecules in ice VII.
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DOI：
10.1038/srep12551
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发表时间：
2015-07-27
影响因子：
4.6
通讯作者：
Irifune T
中科院分区：
文献类型：
--
作者：
Iitaka T;Fukui H;Li Z;Hiraoka N;Irifune T
Guthrie等人最近在高达52GPa的压力下测量了D2O冰的中子衍射图样，他们提出了压力高于13GPa的冰的八面体间隙模型，以解释观察到的晶体结构与冰VII晶体结构的偏差。在本文中，从间隙占据率和X射线拉曼光谱（XRS）光谱方面重新审视了八面体间隙模型。与间隙模型相比，使用第一原理分子动力学模拟计算出的间隙占据率小得可以忽略不计。为间隙模型计算的氧K边光谱显示出两个额外的低能峰，它们分别源自与间隙质子相互作用的水分子和氢氧化物，而这些低能峰在实验测量的光谱中没有观察到。这些结果表明，间隙模型无法解释 VII 在高于 13 GPa 的压力下的 XRS 光谱，并且需要更精确的结构测量和分析来揭示压力引起的转变的本质。
The neutron diffraction pattern of D2O ice was recently measured at pressures up to 52 GPa by Guthrie et al., who proposed an octahedral interstitial model for ice at pressures above 13 GPa to account for the deviation of the observed crystal structure from that of ice VII. In this article, the octahedral interstitial model was re-examined in terms of the interstitial occupancy and X-ray Raman spectroscopy (XRS) spectra. The interstitial occupancy calculated using first-principles molecular dynamics simulations was negligibly small compared to that of the interstitial model. The oxygen K-edge spectra calculated for the interstitial model exhibited two additional low-energy peaks originating from water molecules and hydroxides that are interacting with interstitial protons, respectively, whereas these low-energy peaks were not observed in the experimentally measured spectra. These results suggest that the interstitial model cannot explain the XRS spectra of ice VII at pressures above 13 GPa and that more precise structure measurements and analyses are necessary to reveal the nature of the pressure-induced transition.