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arXiv 0808.2138cond-mat.stat-mechcond-mat.mtrl-sci
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玻璃成型系统中的Specific Heat理论

Theory of Specific Heat in Glass Forming Systems

H. G. E. Hentschel, Valery Ilyin, Itamar Procaccia, Nurith Schupper

摘要:

玻璃形成系统中比热的实验测量揭示了比热的温度依赖性的异常,包括在玻璃化转变附近的所谓的“比热峰”。本文的目的是提供这些异常的理论解释一般和定量理论的情况下,一个简单的模型的玻璃形成。我们首先提出了新的模拟结果的比热在一个经典的二元混合物模型。我们发现,除了以前观察到的比热峰,在较低的温度下,这是在早期的模拟中观察不到的第二个峰。其次,我们提出了比热和体积模量之间的一般关系,从而提供了液体和非晶态固体状态之间的平滑连接。本文的中心结果是在系统中的团簇的微熔化和比热峰的出现之间的连接。我们将这两个峰与体积模量和剪切模量的变化联系起来。我们认为玻璃的形成伴随着体模量和剪切模量的快速变化,但这些快速变化发生在不同的温度范围内。最后,我们演示了如何构建一个理论的频率依赖性复杂的比热,预计从异质集群在液态的玻璃形成。一个具体的例子是在我们的甘油动力学模型的上下文中提供的。与频率相关的比热理论与甘油的实验测量结果吻合得很好。最后,我们指出,在玻璃成型机中,比热的温度依赖性并不普遍-不幸的是,人们需要了解每种情况。

英文摘要:

Experimental measurements of the specific heat in glass-forming systems reveal anomalies in the temperature dependence of the specific heat, including the so called "specific heat peak" in the vicinity of the glass transition. The aim of this paper is to provide theoretical explanations of these anomalies in general and a quantitative theory in the case of a simple model of glass-formation. We first present new simulation results for the specific heat in a classical model of a binary mixture. We show that in addition to the formerly observed specific heat peak there is a second peak at lower temperatures which was not observable in earlier simulations. Second, we present a general relation between the specific heat and the bulk modulus and thus offer a smooth connection between the liquid and amorphous solid states. The central result of this paper is a connection between the micro-melting of clusters in the system and the appearance of specific heat peaks. We relate the two peaks to changes in the bulk and shear moduli. We propose that the phenomenon of glass-formation is accompanied by a fast change in the bulk and the shear moduli, but these fast changes occur in different ranges of the temperature. Lastly, we demonstrate how to construct a theory of the frequency dependent complex specific heat, expected from heterogeneous clustering in the liquid state of glass formers. A specific example is provided in the context of our model for the dynamics of glycerol. The theoretical frequency dependent specific heat agrees well with experimental measurements on glycerol. We conclude the paper by stating that there is nothing universal about the temperature dependence of the specific heat in glass formers - unfortunately one needs to understand each case by itself.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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