Neutron diffraction observations of interstitial protons in dense ice
Neutron diffraction observations of interstitial protons in dense ice
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DOI：
10.1073/pnas.1309277110
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发表时间：
2013-06-25
影响因子：
11.1
通讯作者：
Hemley, Russell J.
中科院分区：
文献类型：
--
作者：
Guthrie, Malcolm;Boehler, Reinhard;Hemley, Russell J.
据信，氢键网络中不同水分子的基序一直持续到冰的最致密分子相。在更高的压力下，分子会解离，通常假设质子仍然位于这些相同的网络内。我们报告了 D2O 的中子衍射测量结果，直接揭示了高达 52 GPa 的 D 原子的位置，这是该技术以前无法达到的压力范围。数据显示结构变化在大约 13 GPa 的压力下开始，并且不能用上面类似于 26 GPa 的冰 VII 的常规网络结构来描述。我们的测量结果与氧晶格八面体间隙空隙中的大量氘核密度一致。对这种“间隙”冰VII形式的观察为理解冰中氢键的演化提供了一个框架，这与传统的图像形成鲜明对比。它也可能是在更高压力下报道的超离子相的前体，对我们对致密物质和行星内部的理解产生重要影响。
The motif of distinct H2O molecules in H-bonded networks is believed to persist up to the densest molecular phase of ice. At even higher pressures, where the molecule dissociates, it is generally assumed that the proton remains localized within these same networks. We report neutron-diffraction measurements on D2O that reveal the location of the D atoms directly up to 52 GPa, a pressure regime not previously accessible to this technique. The data show the onset of a structural change at similar to 13 GPa and cannot be described by the conventional network structure of ice VII above similar to 26 GPa. Our measurements are consistent with substantial deuteron density in the octahedral, interstitial voids of the oxygen lattice. The observation of this "interstitial" ice VII form provides a framework for understanding the evolution of hydrogen bonding in ice that contrasts with the conventional picture. It may also be a precursor for the superionic phase reported at even higher pressure with important consequences for our understanding of dense matter and planetary interiors.