Is High-Density Amorphous Ice Simply a "Derailed" State along the Ice I to Ice IV Pathway?
Is High-Density Amorphous Ice Simply a "Derailed" State along the Ice I to Ice IV Pathway?
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DOI：
10.1021/acs.jpclett.7b00492
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发表时间：
2017-04-06
影响因子：
5.7
通讯作者：
Salzmann, Christoph G.
中科院分区：
文献类型：
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作者：
Shephard, Jacob J.;Ling, Sanliang;Salzmann, Christoph G.
高密度无定形冰（HDA）的结构本质是通过低温压力诱导的“普通”冰I的非晶化形成的，这是有争议的。澄清这个问题不仅对于理解H2O的复杂凝聚态非常重要，而且对于在整个材料谱中遇到的压力诱导非晶化过程的更广泛背景也非常重要。我们首先表明，氟化铵（NH4F），它有一个类似的氢键网络冰I，也经历了压力崩溃后，在77 K压缩。然而，产品材料不是无定形的，而是NH4F II，一种与冰IV同构的高压相。这种崩溃可以用一种高效的机制来解释。在冰I的情况下，水分子的取向无序导致偏离这种机制，因此我们将HDA归类为沿着冰I到冰IV路径的“脱轨”状态。
The structural nature of high-density amorphous ice (HDA), which forms through low-temperature pressure-induced amorphization of the "ordinary" ice I, is heavily debated. Clarifying this question is important for understanding not only the complex condensed states of H2O but also in the wider context of pressure-induced amorphization processes, which are encountered across the entire materials spectrum. We first show that ammonium fluoride (NH4F), which has a similar hydrogen-bonded network to ice I, also undergoes a pressure collapse upon compression at 77 K. However, the product material is not amorphous but NH4F II, a high-pressure phase isostructural with ice IV. This collapse can be rationalized in terms of a highly effective mechanism. In the case of ice I, the orientational disorder of the water molecules leads to a deviation from this mechanism, and we therefore classify HDA as a "derailed" state along the ice I to ice IV pathway.