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首页> 外文期刊>The Journal of Chemical Physics >Analysis of structural correlations in a model binary 3D liquid through the eigenvalues and eigenvectors of the atomic stress tensors
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Analysis of structural correlations in a model binary 3D liquid through the eigenvalues and eigenvectors of the atomic stress tensors

机译：通过原子应力张量的特征值和特征向量分析模型二元3D液体中的结构相关性

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It is possible to associate with every atom or molecule in a liquid its own atomic stress tensor. These atomic stress tensors can be used to describe liquids' structures and to investigate the connection between structural and dynamic properties. In particular, atomic stresses allow to address atomic scale correlations relevant to the Green-Kubo expression for viscosity. Previously correlations between the atomic stresses of different atoms were studied using the Cartesian representation of the stress tensors or the representation based on spherical harmonics. In this paper we address structural correlations in a 3D model binary liquid using the eigenvalues and eigenvectors of the atomic stress tensors. This approach allows to interpret correlations relevant to the Green-Kubo expression for viscosity in a simple geometric way. On decrease of temperature the changes in the relevant stress correlation function between different atoms are significantly more pronounced than the changes in the pair density function. We demonstrate that this behaviour originates from the orientational correlations between the eigenvectors of the atomic stress tensors. We also found correlations between the eigenvalues of the same atomic stress tensor. For the studied system, with purely repulsive interactions between the particles, the eigenvalues of every atomic stress tensor are positive and they can be ordered: lambda(1) >= lambda(2) >= lambda(3) >= 0. We found that, for the particles of a given type, the probability distributions of the ratios (lambda(2)/lambda(1)) and (lambda(3)/lambda(2)) are essentially identical to each other in the liquids state. We also found that lambda(2) tends to be equal to the geometric average of lambda(1) and lambda(3). In our view, correlations between the eigenvalues may represent "the Poisson ratio effect" at the atomic scale. (C) 2016 AIP Publishing LLC.
机译：可以与液体中的每个原子或分子关联自己的原子应力张量。这些原子应力张量可用于描述液体的结构，并研究结构和动态特性之间的联系。特别地，原子应力允许解决与Green-Kubo表达式有关的原子粘度相关性。以前，使用应力张量的笛卡尔表示法或基于球谐函数的表示法研究了不同原子的原子应力之间的相关性。在本文中，我们使用原子应力张量的特征值和特征向量来解决3D模型二元液体中的结构相关性。这种方法允许以简单的几何方式解释与Green-Kubo表达式有关的粘度相关性。随着温度的降低，不同原子之间相关应力相关函数的变化比对密度函数的变化明显得多。我们证明了此行为源自原子应力张量的特征向量之间的取向相关性。我们还发现了相同原子应力张量的特征值之间的相关性。对于研究的系统，在粒子之间具有纯排斥相互作用的情况下，每个原子应力张量的特征值均为正，可以将它们排序：lambda（1）> = lambda（2）> = lambda（3）> =0。我们发现对于给定类型的粒子，比率（lambda（2）/ lambda（1））和（lambda（3）/ lambda（2））的概率分布在液体状态下基本上彼此相同。我们还发现lambda（2）趋于等于lambda（1）和lambda（3）的几何平均值。我们认为，特征值之间的相关性可能表示原子尺度上的“泊松比效应”。 （C）2016 AIP出版有限责任公司。

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