Elastically cooperative activated barrier hopping theory of relaxation in viscous fluids. II. Thermal liquids
Elastically cooperative activated barrier hopping theory of relaxation in viscous fluids. II. Thermal liquids
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DOI：
10.1063/1.4874843
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发表时间：
2014-05-21
影响因子：
4.4
通讯作者：
Schweizer, Kenneth S.
中科院分区：
文献类型：
--
作者：
Mirigian, Stephen;Schweizer, Kenneth S.
基于本文中硬球的弹性集体非线性Langevin方程理论，通过无量纲压缩性将热液体映射到有效硬球流体，提出并实现了热液体α弛豫的准普适理论。其结果是零可调参数理论，可以定量地解决在一个统一的方式超过14个或更多的几十年的α弛豫时间。该理论在零开尔文以上没有奇点，并且在平衡低温极限中的弛豫被预测为大致的Arrhenius形式。两个障碍（本地笼和远程集体弹性）的描述结果在一个丰富的动态行为，包括明显的Arrhenius，窄交叉，深过冷制度，和多个特征或交叉时间和温度的明确的物理意义。应用该理论的非极性分子，醇类，稀有气体和液体金属进行。总的来说，与实验的协议是相当好的温度依赖性的α时间，平台剪切模量，和玻色子样的峰值频率为货车德瓦耳斯液体，虽然不那么氢键分子。该理论预测多个增长的长度尺度冷却后，这反映了耦合的本地跳跃和合作的弹性物理的不同方面。计算的增长与冷却的激活体积，这是强烈相关的动态协同性的措施，同意定量与实验。与弹性，熵危机，动态促进，和其他方法进行比较，并建立了经验提取的交叉温度的基本依据。目前的工作为解决聚合物熔体中独特的玻璃化现象和强约束下的各种液体奠定了基础。(C)2014 AIP Publishing LLC.
Building on the elastically collective nonlinear Langevin equation theory developed for hard spheres in Paper I, we propose and implement a quasi-universal theory for the alpha relaxation of thermal liquids based on mapping them to an effective hard sphere fluid via the dimensionless compressibility. The result is a zero adjustable parameter theory that can quantitatively address in a unified manner the alpha relaxation time over 14 or more decades. The theory has no singularities above zero Kelvin, and relaxation in the equilibrium low temperature limit is predicted to be of a roughly Arrhenius form. The two-barrier (local cage and long range collective elastic) description results in a rich dynamic behavior including apparent Arrhenius, narrow crossover, and deeply supercooled regimes, and multiple characteristic or crossover times and temperatures of clear physical meaning. Application of the theory to nonpolar molecules, alcohols, rare gases, and liquids metals is carried out. Overall, the agreement with experiment is quite good for the temperature dependence of the alpha time, plateau shear modulus, and Boson-like peak frequency for van der Waals liquids, though less so for hydrogen-bonding molecules. The theory predicts multiple growing length scales upon cooling, which reflect distinct aspects of the coupled local hopping and cooperative elastic physics. Calculations of the growth with cooling of an activation volume, which is strongly correlated with a measure of dynamic cooperativity, agree quantitatively with experiment. Comparisons with elastic, entropy crisis, dynamic facilitation, and other approaches are performed, and a fundamental basis for empirically extracted crossover temperatures is established. The present work sets the stage for addressing distinctive glassy phenomena in polymer melts, and diverse liquids under strong confinement. (C) 2014 AIP Publishing LLC.