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arXiv 0903.1933cond-mat.softcond-mat.dis-nn
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致密胶态硬球激活区的动态光散射测量

Dynamic light scattering measurements in the activated regime of dense colloidal hard spheres

Djamel El Masri, Giovanni Brambilla, Matteo Pierno, George Petekidis, Andrew Schofield, Ludovic Berthier, Luca Cipelletti

摘要:

我们使用动态光散射和数值模拟研究的方法来平衡和平衡动力学系统的胶体硬球在很宽的密度范围内,从稀释系统非常集中的悬浮液进行玻璃态动力学。我们讨论了几个实验问题(沉降,热控制,非平衡老化效应,动态异质性)时产生的非常大的弛豫时间进行测量。当分析超过七十年的时间,我们发现,平衡弛豫时间,τ_alpha,我们的系统是由模式耦合理论预测的代数发散超过约三十年的窗口。在较高密度下,τ_alpha随距离呈指数增加,达到临界体积分数phi_0,该临界体积分数phi_0远大于模式耦合奇点。这让人想起了分子玻璃形成者在活化状态下的行为。我们将这些结果与以前的工作进行比较,仔细讨论结晶和尺寸多分散性的影响。我们的研究结果表明,一个真正的代数发散τ_α胶体硬球的情况下。

英文摘要:

We use dynamic light scattering and numerical simulations to study the approach to equilibrium and the equilibrium dynamics of systems of colloidal hard spheres over a broad range of density, from dilute systems up to very concentrated suspensions undergoing glassy dynamics. We discuss several experimental issues (sedimentation, thermal control, non-equilibrium aging effects, dynamic heterogeneity) arising when very large relaxation times are measured. When analyzed over more than seven decades in time, we find that the equilibrium relaxation time, tau_alpha, of our system is described by the algebraic divergence predicted by mode-coupling theory over a window of about three decades. At higher density, tau_alpha increases exponentially with distance to a critical volume fraction phi_0 which is much larger than the mode-coupling singularity. This is reminiscent of the behavior of molecular glass-formers in the activated regime. We compare these results to previous work, carefully discussing crystallization and size polydispersity effects. Our results suggest the absence of a genuine algebraic divergence of tau_alpha in colloidal hard spheres.

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