Feldhoff Armin
Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstraße 3A, D-30167 Hannover, Germany.
Entropy (Basel). 2022 Mar 29;24(4):479. doi: 10.3390/e24040479.
The term thermal capacity appears to suggest a storable thermal quantity. However, this claim is not redeemed when thermal capacity is projected onto "heat", which, like all energy forms, exits only in transit and is not a part of internal energy. The storable thermal quantity is entropy, and entropy capacity is a well-defined physical coefficient which has the advantage of being a susceptibility. The inverse of the entropy capacity relates the response of the system (change of temperature) to a stimulus (change of entropy) such as the fluid level responses to a change in amount of fluid contained in a vessel. Frequently, entropy capacity has been used implicitly, which is clarified in examples of the low-temperature analysis of phononic and electronic contributions to the thermal capacity of solids. Generally, entropy capacity is used in the estimation of the entropy of a solid. Implicitly, the thermoelectric figure of merit refers to entropy capacity. The advantage of the explicit use of entropy capacity comes with a descriptive fundamental understanding of the thermal behaviour of solids, which is made clear by the examples of the Debye model of phonons in solids, the latest thermochemical modelling of carbon allotropes (diamond and graphite) and not least caloric materials. An electrocaloric cycle of barium titanate close to its paraelectric-ferroelectric phase transition is analysed by means of entropy capacity. Entropy capacity is a key to intuitively understanding thermal processes.
热容量这个术语似乎暗示着一种可储存的热量。然而，当热容量被应用于“热”时，这种说法就站不住脚了，因为热像所有能量形式一样，只在传递过程中存在，而不是内能的一部分。可储存的热量是熵，熵容量是一个定义明确的物理系数，它具有磁化率的优势。熵容量的倒数将系统的响应（温度变化）与刺激（熵变化）联系起来，比如容器中液位对所含流体量变化的响应。通常，熵容量是被隐含使用的，这在对固体热容量的声子和电子贡献的低温分析示例中得到了阐明。一般来说，熵容量用于估算固体的熵。隐含地，热电优值指的就是熵容量。明确使用熵容量的优势在于对固体热行为有一个描述性的基本理解，这在固体中声子的德拜模型示例、碳的同素异形体（金刚石和石墨）的最新热化学建模以及尤其重要的是热质材料中都体现得很清楚。通过熵容量分析了接近其顺电 - 铁电相变的钛酸钡的电热循环。熵容量是直观理解热过程的关键。
