标题： 液体和玻璃比热的总能量方法 显示英文标题

标题： The total energy approach for calculating the specific heat of liquids and glasses

摘要： 近年来，通过第一性原理分子动力学（MD）模拟计算液体和玻璃体的比热（$C$）的进展得到了回顾。 液体和玻璃态具有共同的性质，即没有周期性，原子弛豫在其热力学性质中起着重要作用。 长期以来，这些性质阻碍了为这些状态构建适当的$C$理论。 基于密度泛函理论（DFT）的总能量方法提供了一种通用的方法来计算$C$，而不论材料的状态如何。 然而，除了收敛问题之外，即使基于 DFT 的 MD 模拟也会根据 MD 模拟的设置，对液体和玻璃的热力学性质给出不同的值。 根本的问题是原子弛豫，它影响能量与温度$T$之间的关系。 温度由平衡状态决定，但玻璃有许多亚稳态。 亚稳态在其弛豫时间内是稳定的。 我们遇到了滞后现象的困难问题，这是不可逆性的最深刻后果。 不可逆性甚至发生在准静态过程中。 这是热力学文献中最困难和令人困惑的点。 在这里，通过考虑多时间尺度，在绝热 MD 模拟中给出了对平衡性质和不可逆性的一致处理，该模拟没有摩擦项。 热力学第二定律提供了确定平衡的基本原理。 介绍了总能量方法在实际计算中的基本思想和实用性。 显示英文摘要

摘要： The recent development of the calculation of specific heat ($C$) of liquids and glasses by first-principles molecular dynamics (MD) simulations is reviewed. Liquid and glass states have common properties in that there is no periodicity and the atom relaxation has an important role in their thermodynamic properties. These properties have, for a long time, hindered the construction of an appropriate theory of $C$ for these states. The total energy approach based on the density-functional theory (DFT) provides a universal method to calculate $C$, irrespective of the material states. However, aside from the convergence problem, even DFT-based MD simulations give different values for a thermodynamic property of liquids and glasses, depending on the setup of MD simulations. The essential problem is atom relaxation, which affects the relationship between the energy and temperature $T$. The temperature is determined by the equilibrium state, but there are many metastable states for glasses. Metastable states are stable within their relaxation times. We encounter the difficult problem of hysteresis, which is the most profound consequence of irreversibility. Irreversibility occurs even for quasistatic processes. This is the most difficult and confusing point in the thermodynamics literature. Here, a consistent treatment of both equilibrium properties and irreversibility in adiabatic MD simulations, which has no frictional term, is given by taking multi-timescales into account. A leading principle to determine the equilibrium is provided by the second law of thermodynamics. The basic ideas and the usefulness of the total energy approach in real calculations are presented.