From water’s ephemeral dance, a new order emerges
From water’s ephemeral dance, a new order emerges
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从水的短暂舞蹈中，出现了新的秩序
DOI：
10.1073/pnas.1820940116
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Palmer, Jeremy C.
中科院分区：
文献类型：
--
作者：
Palmer, Jeremy C.
液体冷冻成结晶固体是一种普遍存在且熟悉的相变，影响着我们日常生活的许多方面。例如，水的结晶对我们星球的气候和地理以及从食品和能源生产到药物制剂的各种应用具有广泛的影响（1，2）。然而，由于实验能力有限，无法解析引发液体冻结的分子过程，因此结晶的许多方面仍不完全清楚。一个特别令人感兴趣的谜团是冻结和在冷却到熔点Tm以下的液体动力学中观察到的戏剧性变化之间的可能联系。在PNAS中，Fitzner et al. (5)报告了计算机模拟的结果，这些结果揭示了水中这些现象之间的微观联系。不变的热力学定律规定，液体在冷却至Tm以下时将会冻结，但它们没有指定该过程将如何发生或在什么时间尺度上发生（1）。我们对液态水的经验表明，当在环境压力下冷却到熔点Tm= 0 ℃以下时，液态水在环境中容易冻结，结晶相对较快。然而，在其他情况下，它往往被拖延或无限期地停止。在没有杂质或表面促进结晶的情况下，低于Tm的温和冷却产生过冷液相，其可以在不稳定的亚稳平衡状态下存活（1，6）。相比之下，低于玻璃化转变温度Tg Tm的快速冷却产生称为玻璃的无定形固体，其在实验可观察的时间尺度上不会结晶（6，7）。对于水，研究表明过冷液体的温度可低至− 46 C（8）;在大气压下，它可以以低于Tg <$− 137 C的玻璃形式存在（7）。虽然导致结晶的分子过程在玻璃中被动力学阻止，但在过冷液体中情况并非如此。过冷液体中的热波动驱动分子运动（平移和重定向），使其结构在有限的时间尺度上松弛（3）。的
The freezing of a liquid into a crystalline solid is a ubiquitous and familiar phase transition that affects many aspects of our daily life. The crystallization of water, for example, has broad implications for our planet’s climate and geography, and for diverse applications ranging from food and energy production to pharmaceutical formulation (1, 2). Nevertheless, numerous facets of crystallization remain incompletely understood because of the limited ability of experiments to resolve the molecular processes that initiate freezing in liquids. One particularly intriguing mystery is the possible connection between freezing and the dramatic changes observed in the dynamics of liquids cooled below their melting temperature, Tm (3, 4). In PNAS, Fitzner et al.(5) report results from computer simulations that offer a revealing glimpse into the microscopic connection between these phenomena in water. The immutable laws of thermodynamics dictate that a liquid will freeze when cooled below Tm, but they do not specify how, or on what time scale, this process will occur (1). Our experiences with liquid water, which readily freezes in the environment when cooled below its melting point Tm= 0 C at ambient pressure, may suggest that crystallization is relatively swift. Yet, it is often delayed, or arrested indefinitely, in other scenarios. Without impurities or surfaces to promote crystallization, gentle cooling below Tm produces a supercooled liquid phase that can survive in a state of precarious metastable equilibrium (1, 6). Rapid cooling below the glass transition temperature Tg Tm, by contrast, produces an amorphous solid known as a glass that will not crystallize on experimentally observable time scales (6, 7). For water, the supercooled liquid has been studied down to− 46 C (8); at atmospheric pressure, it can exist as a glass below Tg≈− 137 C (7).Although the molecular processes that lead to crystallization are kinetically arrested in glasses, this is not the case in supercooled liquids. Thermal fluctuations in supercooled liquids drive molecular motions (translations and reorientations) that enable their structure to relax on finite time scales (3). The
影响因子：
12.5
作者：
Anisimov, Mikhail A.;Duska, Michal;Sadus, Richard J.
通讯作者：
Sadus, Richard J.
DOI：
10.1073/pnas.1700103114
发表时间：
2017-12-19
影响因子：
11.1
作者：
Handle, Philip H.;Loerting, Thomas;Sciortino, Francesco
通讯作者：
Sciortino, Francesco