The relationship between fragility, configurational entropy and the potential energy landscape of glass-forming liquids
The relationship between fragility, configurational entropy and the potential energy landscape of glass-forming liquids
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DOI：
10.1038/35051524
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发表时间：
2000-11
期刊：
影响因子：
64.8
通讯作者：
S. Sastry
中科院分区：
文献类型：
--
作者：
S. Sastry
玻璃是一种微观上无序的固体物质，当液体以不结晶的方式被冷却或压缩时产生的。几乎所有类型的材料都能形成玻璃，包括聚合物、金属合金和熔盐。考虑到这种多样性，系统地对不同的玻璃形成材料进行分类的一般原则是非常宝贵的。其中一个原则是根据玻璃制品的易碎性对玻璃制品进行分类。脆性是指液体的性质(如粘度)在接近玻璃态时发生变化的速度。尽管之前已经分析了玻璃成型器的脆性、构型熵和能量景观特征(能量对构型的复杂依赖)之间的关系，但对脆性的起源缺乏详细的了解。在这里，我使用模拟来分析模型液体的脆性与能量景观的定量测量之间的关系，该模型液体的脆性取决于其体积密度。结果表明，脆性除了取决于它们的总数和在能量中的扩散外，还取决于单个能量极小值的振动性质的变化。推导出了脆性的热力学表达式，该表达式与由液体扩散系数得到的动力学脆性定量一致。
Glass is a microscopically disordered, solid form of matter that results when a fluid is cooled or compressed in such a manner that it does not crystallize. Almost all types of materials are capable of glass formation, including polymers, metal alloys and molten salts. Given such diversity, general principles by which different glass-forming materials can be systematically classified are invaluable. One such principle is the classification of glass-formers according to their fragility. Fragility measures the rapidity with which a liquid's properties (such as viscosity) change as the glassy state is approached. Although the relationship between the fragility, configurational entropy and features of the energy landscape (the complicated dependence of energy on configuration) of a glass-former have been analysed previously, a detailed understanding of the origins of fragility is lacking. Here I use simulations to analyse the relationship between fragility and quantitative measures of the energy landscape for a model liquid whose fragility depends on its bulk density. The results reveal that fragility depends on changes in the vibrational properties of individual energy minima in addition to their total number and spread in energy. A thermodynamic expression for fragility is derived, which is in quantitative agreement with kinetic fragilities obtained from the liquid's diffusivity.