Strong Correlation Between Atomic-Level Pressures and Viscous Shear Relaxations in Liquids
Strong Correlation Between Atomic-Level Pressures and Viscous Shear Relaxations in Liquids
复制标题
液体中原子级压力与粘性剪切弛豫之间的强相关性
DOI：
10.1007/s11837-019-03889-8
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发表时间：
2020
期刊：
影响因子：
2.6
通讯作者：
and S. Yamada
中科院分区：
文献类型：
--
作者：
T. Iwashita;H. Koga;and S. Yamada
液体无处不在，但由于结构无序和动力学复杂性，粘度的原子起源仍然未知。通过对液态铁的分子动力学模拟，我们发现原子级压力和原子级剪切应力的弛豫之间存在很强的局部相关性，而原子级剪切应力的弛豫与粘度直接相关。结果表明，在压缩状态下的原子位置比在拉伸状态下的原子位置对剪切更不稳定，这导致原子水平的剪切应力的快速弛豫。该结果表明液体中局部粘度的空间不均匀性。我们还发现了一个温度无关的局部剪切弛豫时间和原子级体积应变之间的关系，这表明在液体中的普遍结构动力学关系。为了解释我们的新发现，我们讨论了原子级压力和其他各种参数之间的关系，如原子级剪切应力，von Mises应力，局部配位数和原子的均方位移。
Liquids are ubiquitous, but the atomic origin of viscosity remains unknown because of structural disorder and dynamic complexities. By using molecular dynamics simulation for liquid iron, we find a strong local correlation between the atomic-level pressure and the relaxation of atomic-level shear stress that is directly connected to viscosity. The results show that atomic sites under compression are more unstable against shear than those under tension, which causes fast relaxation in atomic-level shear stress. This result indicates spatial heterogeneities in the local viscosity in a liquid. We also find a temperature-independent relation between the local shear relaxation time and atomic-level volume strain, which suggests a universal structure-dynamics relationship in liquids. To explain our new findings, we discuss the relationships between the atomic-level pressure and various other parameters, such as the atomic-level shear stress, von Mises stress, local coordination number, and mean-squared displacements of atoms.