从四点动态极化率近似和皮秒振动动力学比较动态关联长度
Comparing dynamic correlation lengths from an approximation to the four-point dynamic susceptibility and from the picosecond vibrational dynamics
摘要：
最近，基于慢（皮秒）振动动力学特性，提出了一种测定过冷液体动力学关联长度的新方法[L. Hong，V.N. Novikov和A.P.Sokolov，Phys.Rev.E83，061508（2011）]。尽管这些振动测量通常在远低于玻璃化转变温度Tg的温度下进行，但假设液体的结构在Tg下冻结，使得振动表征过冷液体状态下的动态不均匀性。我们比较从这种方法计算出的值使用近似的四点动态磁化率的的x2。对于26种不同的材料，我们发现这两种措施之间有很好的相关性，而且，压力依赖性是一致的大的实验误差。然而，来自玻色子峰值测量的Tg以上的温度具有不同的、不切实际的温度依赖性。
英文摘要：
Recently a new approach to the determination of dynamic correlation lengths, ξ, for supercooled liquids, based on the properties of the slow (picosecond) vibrational dynamics, was carried out [L. Hong, V.N. Novikov, and A.P. Sokolov, Phys. Rev. E 83, 061508 (2011)]. Although these vibrational measurements are typically conducted well below the glass transition temperature, Tg, the assumption is that the structure of the liquid is frozen at Tg, so that the ξ characterize dynamic heterogeneity in the supercooled liquid state. We compare ξ from this method to values calculated using an approximation to the four-point dynamic susceptibility. For 26 different materials we find good correlation between the two measures; moreover, the pressure dependences are consistent within the large experimental error. However, ξ from Boson peak measurements above Tg have a different, and unrealistic, temperature dependence.
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