Isolating long-wavelength fluctuation from structural relaxation in two-dimensional glass: cage-relative displacement
Isolating long-wavelength fluctuation from structural relaxation in two-dimensional glass: cage-relative displacement
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DOI：
10.1088/1361-648x/aaa8b8
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发表时间：
2018-02
期刊：
影响因子：
--
通讯作者：
H. Shiba;P. Keim;T. Kawasaki
中科院分区：
文献类型：
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作者：
H. Shiba;P. Keim;T. Kawasaki
最近的研究表明，二维（2D）玻璃态系统中存在长波长波动，其起源与二维晶体固体的 Mermin-Wagner 定理给出的起源相同。在本文中，我们讨论了如何定量表征轻度过冷液体分子动力学模拟中的长波长波动。我们采用笼相对均方位移 (MSD)（定义为其笼的相对位移）来定量地将长波长波动与原始 MSD 分开。对于增加系统尺寸，声长波长波动的幅度不仅增加，而且转移到较晚的时间，导致与笼蔽颗粒的结构弛豫交叉。我们使用笼相关量进一步分析动态相关长度。随着温度降低，结构弛豫变得更慢，它会增长，揭示了由于长波长波动而导致的四点相关函数的高估。这些发现促使使用笼相关 MSD 作为分析 2D 玻璃动力学的起点。
It has recently been revealed that long-wavelength fluctuation exists in two-dimensional (2D) glassy systems, having the same origin as that given by the Mermin–Wagner theorem for 2D crystalline solids. In this paper, we discuss how to characterise quantitatively the long-wavelength fluctuation in a molecular dynamics simulation of a lightly supercooled liquid. We employ the cage-relative mean-square displacement (MSD), defined on relative displacement to its cage, to quantitatively separate the long-wavelength fluctuation from the original MSD. For increasing system size the amplitude of acoustic long wavelength fluctuations not only increases but shifts to later times causing a crossover with structural relaxation of caging particles. We further analyse the dynamic correlation length using the cage-relative quantities. It grows as the structural relaxation becomes slower with decreasing temperature, uncovering an overestimation by the four-point correlation function due to the long-wavelength fluctuation. These findings motivate the usage of cage-relative MSD as a starting point for analysis of 2D glassy dynamics.