通过原子尺度格林-库珀应力相关函数对粘滞性的贡献。

Technological Design Institute of Scientific Instrument Engineering, Novosibirsk 630058, Russia.

J Chem Phys. 2017 Nov 14;147(18):184502. doi: 10.1063/1.4991310.

We studied the connection between the structural relaxation and viscosity for a binary model of repulsive particles in the supercooled liquid regime. The used approach is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the correlation functions between the atomic level stresses. Previously we used the approach to study an iron-like single component system of particles. The role of vibrational motion has been addressed through the demonstration of the relationship between viscosity and the shear waves propagating over large distances. In our previous considerations, however, we did not discuss the role of the structural relaxation. Here we suggest that the contribution to viscosity from the structural relaxation can be taken into account through the consideration of the contribution from the atomic stress auto-correlation term only. This conclusion, however, does not mean that only the auto-correlation term represents the contribution to viscosity from the structural relaxation. Previously the role of the structural relaxation for viscosity has been addressed through the considerations of the transitions between inherent structures and within the mode-coupling theory by other authors. In the present work, we study the structural relaxation through the considerations of the parent liquid and the atomic level stress correlations in it. The comparison with the results obtained on the inherent structures also is made. Our current results suggest, as our previous observations, that in the supercooled liquid regime, the vibrational contribution to viscosity extends over the times that are much larger than the Einstein's vibrational period and much larger than the times that it takes for the shear waves to propagate over the model systems. Besides addressing the atomic level shear stress correlations, we also studied correlations between the atomic level pressure elements.

我们研究了过冷液体状态下排斥粒子二元模型的结构弛豫与粘性之间的关系。所采用的方法基于将宏观格林-库珀应力相关函数分解为原子级应力之间的相关函数。我们之前曾使用该方法研究过类似于铁的单一成分粒子系统。通过证明粘性与远距离传播的剪切波之间的关系，已经研究了振动运动的作用。然而，在我们之前的考虑中，我们没有讨论结构弛豫的作用。在这里，我们建议仅通过考虑原子应力自相关项，就可以考虑结构弛豫对粘性的贡献。但是，这个结论并不意味着只有自相关项代表结构弛豫对粘性的贡献。先前，其他作者已经通过考虑本征结构之间的转变以及模式耦合理论来研究结构弛豫对粘性的作用。在目前的工作中，我们通过考虑母体液体及其原子级应力相关来研究结构弛豫。还与从本征结构获得的结果进行了比较。我们当前的结果表明，与我们之前的观察结果一样，在过冷液体状态下，粘性的振动贡献扩展到远大于爱因斯坦振动周期的时间，并且大于剪切波在模型系统中传播的时间。除了研究原子级剪切应力相关性外，我们还研究了原子级压力元素之间的相关性。