发表机构
Jawaharlal Nehru Centre for Advanced Scientific Research; University of Montpellier, CNRS（贾瓦哈拉尔·尼赫鲁高级科学研究中心; 蒙彼利埃大学，法国国家科学研究中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究提出四点相关函数，发现笼各向异性中程序在玻璃形成液体的两个动力学交叉温度处达到峰值，从而将结构变化与输运机制改变联系起来。
AI 中文摘要
在将液体冷却至其玻璃化转变温度的过程中，弛豫时间的急剧增加伴随着粒子动力学在两种不同温度下的变化：一个高温交叉，其中粒子暂时被其邻居笼蔽；以及一个低温交叉，其中笼逃逸机制发生变化。虽然有证据表明前者与局部粒子排列的变化有关，但迄今为止尚未在低温交叉中检测到结构修饰，这加剧了人们对结构在玻璃态动力学中相关性的怀疑。在此，我们引入了一种新的四点相关函数，该函数能够确定表征笼各向异性的结构长度尺度。广泛的分子动力学模拟表明，该尺度以及玻璃形成体的平均结构长度尺度延伸至中程，即显著超过粒子尺寸。引人注目的是，这两个尺度之间的差异——笼各向异性程度的度量——在两个交叉温度下均达到峰值。我们讨论了这些峰的存在如何有助于理解两种温度下微观输运机制变化的本质，从而将两个动力学交叉与单一结构可观测值——各向异性中程序——联系起来。这一基本见解表明，结构远远超出局部笼的范围，是理解深度过冷液体弛豫动力学的基本要素。
英文摘要
On cooling liquids towards their glass-transition temperature, the dramatic increase of their relaxation times is accompanied by changes in particle dynamics at two distinct temperatures: A high-T crossover, where particles become temporarily caged by their neighbors, and a low-T crossover, where the cage escape mechanism changes. While there is some evidence that the former is associated with a change in local particle arrangement, no structural modification has so far been detected across the low-T crossover, fueling scepticism about the relevance of structure for glassy dynamics. Here, we introduce a novel four-point correlation function which allows to determine a structural length scale characterizing cage anisotropy. Extensive molecular dynamics simulations reveal that this scale, as well as the mean structural length scale of the glass-former, extends into the medium range, i.e., significantly exceeds the particle size. Strikingly, the difference between these two scales - a measure of the degree of cage anisotropy - peaks at both crossover temperatures. We discuss how the presence of these peaks enables understanding the nature of the change in the microscopic transport mechanism at the two temperatures, thereby linking both dynamical crossovers to a single structural observable, the anisotropic medium-range order. This fundamental insight demonstrates that structure, extending well-beyond the local cage, is an essential ingredient for understanding the relaxation dynamics of deeply supercooled liquids.
