Berthier L, Biroli G, Bouchaud J-P, Kob W, Miyazaki K, Reichman D R
Laboratoire des Colloïdes, Verres et Nanomatériaux, UMR 5587, Université Montpellier II-CNRS, 34095 Montpellier, France.
J Chem Phys. 2007 May 14;126(18):184503. doi: 10.1063/1.2721554.
We study theoretically and numerically a family of multipoint dynamic susceptibilities that quantify the strength and characteristic length scales of dynamic heterogeneities in glass-forming materials. We use general theoretical arguments (fluctuation-dissipation relations and symmetries of relevant dynamical field theories) to relate the sensitivity of averaged two-time correlators to temperature and density to spontaneous fluctuations of the local dynamics. Our theoretical results are then compared to molecular dynamics simulations of the Newtonian, Brownian, and Monte Carlo dynamics of two representative glass-forming liquids, a fragile binary Lennard-Jones mixture, and a model for the strong glass-former silica. We justify in detail the claim made by Berthier et al. [Science 310, 1797 (2005)] that the temperature dependence of correlation functions allows one to extract useful information on dynamic length scales in glassy systems. We also discuss some subtle issues associated with the choice of microscopic dynamics and of statistical ensemble through conserved quantities, which are found to play an important role in determining dynamic correlations.
我们从理论和数值上研究了一类多点动态磁化率，这类磁化率量化了玻璃形成材料中动态不均匀性的强度和特征长度尺度。我们使用一般理论论据（涨落耗散关系和相关动力学场论的对称性），将平均二次关联函数对温度和密度的敏感性与局部动力学的自发涨落联系起来。然后，我们将理论结果与两种代表性玻璃形成液体（一种是脆性二元 Lennard-Jones 混合物，另一种是强玻璃形成体二氧化硅的模型）的牛顿动力学、布朗动力学和蒙特卡罗动力学进行分子动力学模拟相比较。我们详细论证了 Berthier 等人 [《科学》310, 1797 (2005)] 提出的观点，即关联函数的温度依赖性使人们能够提取有关玻璃态系统中动态长度尺度的有用信息。我们还讨论了一些与通过守恒量选择微观动力学和统计系综相关的微妙问题，发现这些问题在确定动态关联方面起着重要作用。
