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arXiv 1202.1127cond-mat.dis-nn
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玻璃态动力学中的弛豫机制:Arbidius和Fragile区

Relaxation Mechanisms in Glassy Dynamics: the Arrhenius and Fragile Regimes

H. George E. Hentschel, Smarajit Karmakar, Itamar Procaccia, Jacques Zylberg

摘要:

一般的玻璃形成体在其松弛行为中表现出至少两种特征性变化,首先是在某一特征温度下的Arrhenius型松弛,然后是在较低的特征温度下的超Arrhenius(脆性)行为。我们通过研究不同温度和空间维度下不同系统的自由能垒的统计数据来解决这些转变。我们提出了一个明确的证据的动力学行为的变化,在过渡到Arrhenius,然后超Arrhenius行为。提出了一个简单的模型,基于单粒子和合作动力学之间的竞争的想法。我们认为,只要有足够的自由体积完成一个简单的$T_1$弛豫过程,阿克里乌斯行为可以发生。一旦没有自由体积,就需要一种合作机制来“收集”足够的自由体积。我们表明,该模型捕捉到所有的定性行为在整个考虑的温度范围内的模拟中观察到的。

英文摘要:

Generic glass formers exhibit at least two characteristic changes in their relaxation behavior, first to an Arrhenius-type relaxation at some characteristic temperature, and then at a lower characteristic temperature to a super-Arrhenius (fragile) behavior. We address these transitions by studying the statistics of free energy barriers for different systems at different temperatures and space dimensions. We present a clear evidence for changes in the dynamical behavior at the transition to Arrhenius and then to a super-Arrhenius behavior. A simple model is presented, based on the idea of competition between single-particle and cooperative dynamics. We argue that Arrhenius behavior can take place as long as there is enough free volume for the completion of a simple $T_1$ relaxation process. Once free volume is absent one needs a cooperative mechanism to `collect' enough free volume. We show that this model captures all the qualitative behavior observed in simulations throughout the considered temperature range.

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