用三重关联函数研究液态和玻璃态简谐排斥体系的结构
Structure of the simple harmonic-repulsive system in liquid and glassy states studied by the triple correlation function
摘要：
一个有效的描述的结构的液体，特别是，结构的变化，发生与液体过冷仍然是一个挑战。在这种情况下，由软粒子组成的系统特别有趣，因为它们经常表现出不允许引入最近邻壳的概念的非平凡局部序。由于这个原因，一些用于原子液体结构分析的方法在软粒子体系中的应用是值得怀疑的。在这里，我们报告了我们的调查的结构简单的谐波排斥液体在3D使用三重关联函数（TCF），即，不依赖于最近邻概念的方法。该液体被认为处于减压（$P=1.8$）下，在该减压下，它表现出显著的抗冷却结晶的稳定性。它表明，TCF允许解决的结构，不允许从键取向序参量的研究得出明确的结论的取向相关性的发展。我们的研究结果表明，取向的相关性，如果测量的TCF中的峰的高度，显着增加冷却。这种取向有序的上升并没有被柯克伍德的叠加近似正确地捕捉到。对TCF中峰的形状的详细考虑表明取向有序和系统动力学的减慢之间存在联系。我们的研究结果支持这样的观点，即液体中的取向相关性的发展可能在液体的动力学中起着重要的作用，并且对分布函数的考虑可能不足以直观地理解液体在过冷时发生的所有结构变化。
英文摘要：
An efficient description of the structures of liquids and, in particular, the structural changes that happen with liquids on supercooling remains to be a challenge. The systems composed of soft particles are especially interesting in this context because they often demonstrate non-trivial local orders that do not allow to introduce the concept of the nearest-neighbor shell. For this reason, the use of some methods, developed for the structure analysis of atomic liquids, is questionable for the soft-particle systems. Here we report about our investigations of the structure of the simple harmonic-repulsive liquid in 3D using the triple correlation function (TCF), i.e., the method that does not rely on the nearest neighbor concept. The liquid is considered at reduced pressure ($P=1.8$) at which it exhibits remarkable stability against crystallization on cooling. It is demonstrated that the TCF allows addressing the development of the orientational correlations in the structures that do not allow drawing definite conclusions from the studies of the bond-orientational order parameters. Our results demonstrate that the orientational correlations, if measured by the heights of the peaks in the TCF, significantly increase on cooling. This rise in the orientational ordering is not captured properly by the Kirkwood's superposition approximation. Detailed considerations of the peaks' shapes in the TCF suggest the existence of a link between the orientational ordering and the slowdown of the system's dynamics. Our findings support the view that the development of the orientational correlations in liquids may play a significant role in the liquids' dynamics and that the considerations of the pair distribution function may not be sufficient to understand intuitively all the structural changes that happen with liquids on supercooling.
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