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arXiv 2512.12759cond-mat.stat-mech
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从频率依赖的比热到玻璃液体的拟温度

From Frequency Dependent Specific Heat to Fictive Temperature of a Glassy Liquid

Biman Bagchi

AI总结:

本文通过线性响应理论,将拟温度的时间依赖性与记忆函数联系起来,揭示了玻璃液体在淬火过程中的非平衡态行为,并通过自洽计算分析了二氧化硅中弛豫函数与比热的关系。

摘要:

在快速淬火温度下,玻璃形成液体的系统由于其有限的弛豫时间而离开平衡状态。此外,随着时间的推移,弛豫过程变得越来越慢。所创建的非平衡状态可以通过引入一个拟温度来方便地描述,该拟温度提供了非平衡系统的即时状态。拟温度T_f(t)是时间依赖的。在冷却过程中,拟温度高于实际温度。在冷却或淬火停止后,拟温度以依赖于液体弛豫性质的速率接近最终温度。在本工作中,我们利用线性响应理论将拟温度的时间依赖性与记忆函数联系起来,后者已被证明与频率依赖的比热有关,而比热本身又依赖于拟温度T_f(t)。因此,需要进行自洽计算以捕捉弛豫率和结构响应函数之间的相互依赖性。我们提出了一个数值计算,其中我们将关系应用于二氧化硅,其中描述频率依赖比热的弛豫函数被建模为威廉-瓦茨(WW)函数,而弛豫时间被建模为沃格尔-弗勒奇-塔曼(VFT)函数。我们自洽地计算了拟温度。T_f(t)随着时间(t)的推移表现出从实际温度的下降。

英文摘要:

Upon rapid quenching of temperature of a glass forming liquid, the system falls out of equilibrium due its finite relaxation time. Additionally, the relaxation becomes progressively slower with time. The created nonequilibrium state of the glassy system is conveniently described by introducing a fictive temperature which provides the instantaneous state of the nonequilibrium system. The fictive temperature $T_{f} (t)$ is time dependent. During cooling, the fictive temperature is higher than the actual temperature. After the cooling or quenching has ceased, the fictive temperature approaches the final temperature at a rate that depends on the relaxation properties of the liquid. In this work we use linear response theory to connect the time dependence of the fictive temperature to memory function which is shown to be related to the frequency dependent specific heat which itself depends on the fictive temperature $T_{f} (t)$. Thus, one requires { \it a self-consistent calculation} to capture the interdependence of relaxation rate and structural response function. We present a numerical calculation where we apply our relations to silica where the relaxation function that describes the frequency dependent specific heat and is modeled as a stretched exponential William-Watts (WW) function, while the relaxation time is modeled as a Vogel-Fulcher-Tammann (VFT). We calculate the fictive temperature self-consistently. $T_{f}(t)$ exhibits the fall out from actual temperature as time (t) progresses.

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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