THE OLD PROBLEMS OF GLASS AND THE GLASS-TRANSITION, AND THE MANY NEW TWISTS
THE OLD PROBLEMS OF GLASS AND THE GLASS-TRANSITION, AND THE MANY NEW TWISTS
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DOI：
10.1073/pnas.92.15.6675
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发表时间：
1995-07-18
影响因子：
11.1
通讯作者：
ANGELL, CA
中科院分区：
文献类型：
--
作者：
ANGELL, CA
本文回顾了在自然界和材料科学中获得玻璃态的方法，并着重介绍了一个“新的转折点”--最近对玻璃态中多晶现象的认识，即通过连续冷却形成玻璃然后检查（粘性减慢），审查强/易碎液体分类，一个新的扭曲的可能性，即减速是一个避免的临界点的结果，指出，三个典型的特征松弛液体通过相关的脆弱性。作为一个新的转折，强液体的转变，脆性液体的压力诱导的配位数增加被证明，然后表明，对于可比系统，它是可能的，有相同的转换，通过一个一级转变内的液体状态在淬火过程中完成，这发生在系统中，“多晶”（在玻璃态中的多态性）被观察到，并且整个现象由Poole的键修正的货车der Waals模型来解释。通过这种弱的一级转变，一些液体自由度的突然损失然后与天然和变性水合蛋白质之间的多态性转变有关，因为后者也是玻璃形成系统-水增塑的、氢键交联的链聚合物通过注意到蛋白质物理学家大量研究的短时间尺度现象-即，d [r（2）] /dT（[r（2）]是Debye-Waller因子）的急剧变化的开始-对于玻璃形成液体是普遍的，包括计算机模拟的强离子液体和脆性离子液体，并且与实验玻璃化转变温度密切相关。因此，后者起源于振动态密度的某些组分中的强非谐性，这允许系统进入其构型空间的多个最小值。这些模式中的非谐性，振动局域化，Kauzmann温度，提出了液体的脆性是玻璃科学中的关键问题。
In this paper I review the ways in which the glassy state is obtained both in nature and in materials science and highlight a ''new twist''-the recent recognition of polymorphism within the glassy state, The formation of glass by continuous cooling (viscous slowdown) is then examined, the strong/fragile liquids classification is reviewed, and a new twist-the possibility that the slowdown is a result of an avoided critical point-is noted, The three canonical characteristics of relaxing liquids are correlated through the fragility. As a further new twist, the conversion of strong liquids to fragile liquids by pressure-induced coordination number increases is demonstrated, It is then shown that, for comparable systems, it is possible to have the same conversion accomplished via a first-order transition within the liquid state during quenching, This occurs in the systems in which ''polyamorphism'' (polymorphism in the glassy state) is observed, and the whole phenomenology is accounted for by Poole's bond-modified van der Waals model, The sudden loss of some liquid degrees of freedom through such weak first-order transitions is then related to the polyamorphic transition between native and denatured hydrated proteins, since the latter are also glass-forming systems-water-plasticized, hydrogen bond-cross-linked chain polymers (and single molecule glass formers), The circle is closed with a final new twist by noting that a short time scale phenomenon much studied by protein physicists-namely, the onset of a sharp change in d [r(2)] /dT ([r(2)] is the Debye-Waller factor)-is general for glass-forming liquids, including computer-simulated strong and fragile ionic liquids, and is closely correlated with the experimental glass transition temperature, The latter thus originates in strong anharmonicity in certain components of the vibrational density of states, which permits the system to access the multiple minima of its configuration space, The connection between the anharmonicity in these modes, vibrational localization, the Kauzmann temperature, and the fragility of the liquid is proposed as the key problem in glass science.