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首页> 外文期刊>The Journal of Chemical Physics >Multi-time density correlation functions in glass-forming liquids: Probing dynamical heterogeneity and its lifetime
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Multi-time density correlation functions in glass-forming liquids: Probing dynamical heterogeneity and its lifetime

机译：形成玻璃的液体中的多次密度相关函数：探测动态异质性及其寿命

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摘要

A multi-time extension of a density correlation function is introduced to reveal temporal information about dynamical heterogeneity in glass-forming liquids. We utilize a multi-time correlation function that is analogous to the higher-order response function analyzed in multidimensional nonlinear spectroscopy. Here, we provide comprehensive numerical results of the four-point, three-time density correlation function from longtime trajectories generated by molecular dynamics simulations of glass-forming binary soft-sphere mixtures. We confirm that the two-dimensional representations in both time and frequency domains are sensitive to the dynamical heterogeneity and that these reveal the couplings of correlated motions, which exist over a wide range of time scales. The correlated motions detected by the three-time correlation function are divided into mobile and immobile contributions that are determined from the particle displacement during the first time interval. We show that the peak positions of the correlations are in accord with the information on the non-Gaussian parameters of the van Hove self-correlation function. Furthermore, it is demonstrated that the progressive changes in the second time interval in the three-time correlation function enable us to analyze how correlations in dynamics evolve in time. From this analysis, we evaluated the lifetime of the dynamical heterogeneity and its temperature dependence systematically. Our results show that the lifetime of the dynamical heterogeneity becomes much slower than the α -relaxation time that is determined from the two-point density correlation function when the system is highly supercooled.
机译：引入了密度相关函数的多次扩展，以揭示有关玻璃形成液体中动态异质性的时间信息。我们利用了类似于多维非线性光谱中分析的高阶响应函数的多次相关函数。在这里，我们提供了由形成玻璃的二元软球混合物的分子动力学模拟产生的长期轨迹得出的四点，三倍密度相关函数的综合数值结果。我们确认时域和频域中的二维表示都对动态异质性敏感，并且这些揭示了相关运动的耦合，这些运动存在于很宽的时间范围内。由三时间相关函数检测到的相关运动分为移动和固定贡献，这是根据第一时间间隔内的粒子位移确定的。我们表明，相关的峰值位置与关于范霍夫自相关函数的非高斯参数的信息一致。此外，证明了三时间相关函数中第二时间间隔的逐步变化使我们能够分析动力学中的相关如何随时间演变。通过此分析，我们系统地评估了动态异质性的寿命及其温度依赖性。我们的结果表明，当系统高度过冷时，动态异质性的寿命变得比根据两点密度相关函数确定的α松弛时间要慢得多。

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