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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Fragility of liquids using percolation-based transport theories - Correlation between limiting slope of the viscosity and non-exponentiality of relaxation
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Fragility of liquids using percolation-based transport theories - Correlation between limiting slope of the viscosity and non-exponentiality of relaxation

机译：使用基于渗流的输运理论的液体易碎性-粘度极限斜率与弛豫的非指数性之间的相关性

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Transport in super-cooled liquids becomes increasingly heterogeneous with reduction in temperature. This transport is assumed to occur by thermally activated hopping over barriers. At a temperature defined here to be T-c, transport becomes percolative rather than diffusive, and, especially for mechanical relaxation, larger energy barriers must be surmounted in order to establish steady-state response. Use of the same distribution of energy barriers at high and low temperatures, but different theoretical approaches to calculate transport properties, relates expressions for the viscosity at high and low temperatures. Such an approach also allows calculation here of an expression relating the limiting slope, m, of the viscosity to the parameters of an assumed log-normal distribution of energy barriers. Careful calculation of the frequency dependence of transport properties in terms of this distribution of energy barriers also allows expression of the non-exponentiality parameter, beta, in terms of the same parameters. Analytical calculations of both (within established approximation schemes) allows quantitative comparison between m and beta. The analytical results are evaluated using typical frequencies and times from experiment. Agreement between experiment and calculations is fair. Nevertheless, sensitivity of the calculations to uncertainty in the values of the experimentally derived parameters makes it necessary to view the correspondence with caution. It is tentatively concluded that the major component of the curvature of the viscosity with decreasing temperature is indeed the change in transport type, and not changes in structure. Advances in theory as well as application of numerical methods are needed to help to reduce uncertainty in the conclusions. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 37]
机译：随着温度的降低，在过冷液体中的运输变得越来越不均匀。假定这种传输是通过热激活跃迁越过障碍而发生的。在此处定义为T-c的温度下，传输变得渗透而不是扩散，并且，特别是对于机械松弛，必须克服较大的能垒才能建立稳态响应。在高温和低温下使用相同分布的能垒，但使用不同的理论方法来计算运输性质，则涉及高温和低温下的粘度表达式。这种方法在此还允许计算将粘度的极限斜率m与假定的能垒的对数正态分布的参数相关的表达式。根据能垒的这种分布仔细地计算传输特性的频率依赖性，还可以用相同的参数表示非指数参数β。两者的分析计算（在已建立的近似方案内）允许对m和beta进行定量比较。使用实验中的典型频率和时间评估分析结果。实验和计算之间的协议是公平的。但是，由于计算对实验得出的参数值的不确定性具有敏感性，因此必须谨慎查看对应关系。初步得出结论，随着温度降低，粘度曲率的主要成分确实是运输类型的改变，而不是结构的改变。需要理论上的进步以及数值方法的应用来帮助减少结论的不确定性。 （C）2000 Elsevier Science B.V.保留所有权利。 [参考：37]

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