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arXiv 1401.4485cond-mat.stat-mechcond-mat.dis-nn
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玻璃态的动力学异质结

Dynamical Heterogeneity in the Glassy State

Apiwat Wisitsorasak, Peter G. Wolynes

摘要:

我们比较了在平衡过冷液体和非平衡玻璃态的随机一级跃迁理论的框架内的动力学不均匀性。波动的迁移率的产生和运输的玻璃处理通过数值求解随机连续方程的迁移率和虚构的温度场,所产生的扩展模式耦合理论,包含激活事件。在老化和再生玻璃中的波动时空结构导致玻璃中的动态不均匀性,其特征不同于在平衡过冷液体中发现的那些。随着四点关联函数的非高斯分布的活化自由能,拉伸指数$β$,和特征长度的增长进行了研究。加热和冷却时的非对称热力学响应被预测为低于$T_g$的玻璃的非均匀性和非平衡行为的结果。数值计算结果与实验量热法一致。我们在数值上证实了Lubchenko和Wolynes在玻璃中的预测,即动力学不均匀性可以导致局部虚构温度出现明显的双峰分布,这以统一的方式解释了最近的实验观察结果,这些观察结果被解释为来自玻璃中的两种不同的平衡机制。

英文摘要:

We compare dynamical heterogeneities in equilibrated supercooled liquids and in the nonequilibrium glassy state within the framework of the random first order transition theory. Fluctuating mobility generation and transport in the glass are treated by numerically solving stochastic continuum equations for mobility and fictive temperature fields that arise from an extended mode coupling theory containing activated events. Fluctuating spatiotemporal structures in aging and rejuvenating glasses lead to dynamical heterogeneity in glasses with characteristics distinct from those found in the equilibrium supercooled liquid. The non-Gaussian distribution of activation free energies, the stretching exponent $β$, and the growth of characteristic lengths are studied along with the four-point correlation function. Asymmetric thermodynamic responses upon heating and cooling are predicted to be the results of the heterogeneity and the out-of-equilibrium behavior of glasses below $T_g$. Numerical results agree with experimental calorimetry. We numerically confirm the prediction of Lubchenko and Wolynes in the glass that the dynamical heterogeneity can lead to noticeably bimodal distributions of local fictive temperatures which explains in a unified way recent experimental observations that have been interpreted as coming from two distinct equilibration mechanisms in glasses.

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