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arXiv 0902.3255cond-mat.mtrl-scicond-mat.dis-nncond-mat.stat-mech
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玻璃形成液体中动力学倾向的空间相关性

Spatial Correlation of the Dynamic Propensity in a Glass-Forming Liquid

M. Shajahan G. Razul, Gurpreet S. Matharoo, Peter H. Poole

摘要:

我们提出了关于动态倾向的计算机模拟结果[如Widmer-Cooper,Harrowell和Fynewever,Phys. Rev. Lett. 93,135701(2004)]在由8788个粒子组成的Kob-Andersen二元Lennard-Jones液体系统中。我们计算的空间关联函数的动态倾向作为一个函数的约化温度T,和时间尺度上的粒子位移进行测量。对于T \leq 0.6,我们发现,非零相关性发生在我们的系统中可访问的最大长度尺度。我们还表明,一个集群大小分析的动态倾向,以及3D可视化的极值粒子,揭示了空间相关的区域,接近我们的系统的大小作为T减少,与空间关联函数的行为一致。接下来,我们定义并研究了“配位倾向”,即围绕多数A粒子的少数B粒子的配位数的等构型平均值。我们发现,一个显着的相关性之间存在的空间波动的动态和协调倾向。此外,我们发现非零相关的协调倾向发生在我们的系统中可访问的最大长度尺度的所有T在范围0.466<T<1.0。我们讨论了这些结果的影响,了解玻璃形成液体的动态不均匀性的长度尺度。

英文摘要:

We present computer simulation results on the dynamic propensity [as defined by Widmer- Cooper, Harrowell, and Fynewever, Phys. Rev. Lett. 93, 135701 (2004)] in a Kob-Andersen binary Lennard-Jones liquid system consisting of 8788 particles. We compute the spatial correlation function of the dynamic propensity as a function of both the reduced temperature T, and the time scale on which the particle displacements are measured. For T\leq0.6, we find that nonzero correlations occur at the largest length scale accessible in our system. We also show that a cluster-size analysis of particles with extremal values of the dynamic propensity, as well as 3D visualizations, reveal spatially correlated regions that approach the size of our system as T decreases, consistent with the behavior of the spatial correlation function. Next, we define and examine the "coordination propensity", the isoconfigurational average of the coordination number of the minority B particles around the majority A particles. We show that a significant correlation exists between the spatial fluctuations of the dynamic and coordination propensities. In addition, we find non-zero correlations of the coordination propensity occurring at the largest length scale accessible in our system for all T in the range 0.466<T<1.0. We discuss the implications of these results for understanding the length scales of dynamical heterogeneity in glass-forming liquids.

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