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Absence of amorphous forms when ice is compressed at low temperature
Nature ( IF 50.5 ) Pub Date : 2019-05-22 , DOI: 10.1038/s41586-019-1204-5
Chris A Tulk 1 , Jamie J Molaison 1 , Adam R Makhluf 2 , Craig E Manning 2 , Dennis D Klug 3
Affiliation  

Amorphous water ice comes in at least three distinct structural forms, all lacking long-range crystalline order. High-density amorphous ice (HDA) was first produced by compressing ice I to 11 kilobar at temperatures below 130 kelvin, and the process was described as thermodynamic melting1, implying that HDA is a glassy state of water. This concept, and the ability to transform HDA reversibly into low-density amorphous ice, inspired the two-liquid water model, which relates the amorphous phases to two liquid waters in the deeply supercooled regime (below 228 kelvin) to explain many of the anomalies of water2 (such as density and heat capacity anomalies). However, HDA formation has also been ascribed3 to a mechanical instability causing structural collapse and associated with kinetics too sluggish for recrystallization to occur. This interpretation is supported by simulations3, analogy with a structurally similar system4, and the observation of lattice-vibration softening as ice is compressed5,6. It also agrees with recent observations of ice compression at higher temperatures—in the ‘no man’s land’ regime, between 145 and 200 kelvin, where kinetics are faster—resulting in crystalline phases7,8. Here we further probe the role of kinetics and show that, if carried out slowly, compression of ice I even at 100 kelvin (a region in which HDA typically forms) gives proton-ordered, but non-interpenetrating, ice IX′, then proton-ordered and interpenetrating ice XV′, and finally ice VIII′. By contrast, fast compression yields HDA but no ice IX, and direct transformation of ice I to ice XV′ is structurally inhibited. These observations suggest that HDA formation is a consequence of a kinetically arrested transformation between low-density ice I and high-density ice XV′ and challenge theories that connect amorphous ice to supercooled liquid water.Slow compression of ice at low temperature results in the sequential formation of a series of crystalline phases, challenging theories that connect amorphous ice to supercooled liquid water.

中文翻译:

冰在低温下压缩时不存在无定形形式

无定形水冰至少有三种不同的结构形式,都缺乏长程结晶顺序。高密度无定形冰 (HDA) 最初是通过在低于 130 开尔文的温度下将冰 I 压缩到 11 千巴而产生的,该过程被描述为热力学熔化 1,这意味着 HDA 是一种玻璃态的水。这一概念以及将 HDA 可逆地转化为低密度无定形冰的能力启发了双液态水模型,该模型将无定形相与深度过冷状态(低于 228 开尔文)中的两种液态水联系起来,以解释许多异常现象水2(例如密度和热容异常)。然而,HDA 的形成也被归因于机械不稳定性导致结构坍塌,并且与动力学太慢而无法发生再结晶有关。这种解释得到了模拟 3 的支持,类似于结构相似的系统 4,以及冰被压缩时晶格振动软化的观察 5,6。它还与最近对更高温度下冰压缩的观察结果一致——在“无人区”状态下,在 145 到 200 开尔文之间,其中动力学更快——导致结晶相7,8。在这里,我们进一步探讨了动力学的作用,并表明,如果缓慢进行,即使在 100 开尔文(HDA 通常形成的区域)下压缩冰 I 也会产生质子有序但非互穿的冰 IX',然后质子-有序和相互渗透的冰 XV',最后是冰 VIII'。相比之下,快速压缩产生 HDA 但没有冰 IX,并且冰 I 到冰 XV' 的直接转化在结构上受到抑制。
更新日期:2019-05-22
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