Frequency dependence and equilibration of the specific heat of glass-forming liquids.
Frequency dependence and equilibration of the specific heat of glass-forming liquids.
复制标题
玻璃形成液体的比热的频率依赖性和平衡。
DOI：
10.1103/physreve.69.051201
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Carruzzo,HervéM
中科院分区：
文献类型：
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作者：
Yu,ClareC;Carruzzo,HervéM
我们已经进行了分子动力学模拟的玻璃形成液体组成的三维二元混合物的软球。我们表明，在比热与温度的峰值可以发生，因为玻璃系统，没有老化的迹象，通过能源景观进展缓慢，需要获得准确的热力学平均值的最小采样时间超过了观察时间。我们开发了一个系统的技术来确定比热的平衡值和最小采样时间。在比热峰温度以下，最小取样时间比弛豫时间长几个数量级。我们发现，一个平衡的系统，不经历结构松弛或老化有一个频率依赖的比热，随着频率的降低而上升。上升发生在对应于周期的频率处，该周期足够长以使系统对统计上独立的能量进行采样。当周期与最小采样时间相当时，频率依赖比热达到平台。因此，比热具有频率依赖性，其频率数量级低于反向弛豫时间所暗示的频率数量级。
We have performed molecular dynamics simulations on a glass-forming liquid consisting of a three-dimensional binary mixture of soft spheres. We show that a peak in the specific heat versus temperature can occur because a glassy system that shows no signs of aging progresses so slowly through the energy landscape that the minimum sampling time needed to obtain accurate thermodynamic averages exceeds the observation time. We develop a systematic technique to determine the equilibrium value of the specific heat and the minimum sampling time. Below the temperature of the specific heat peak, the minimum sampling time is orders of magnitude longer than therelaxation time. We find that an equilibrium system that is not undergoing structural relaxation or aging has a frequency dependent specific heat that rises as the frequency decreases. The rise occurs at frequencies corresponding to periods that are long enough for the system to sample statistically independent energies. When the period is comparable to the minimum sampling time, the frequency dependent specific heat reaches a plateau. As a result, the specific heat has a frequency dependence at frequencies orders of magnitude lower than is implied by the inverserelaxation time.