Thermodynamic Potentials and Natural Variables

Abstract Most books on Thermodynamics explain what thermodynamic potentials are and how conveniently they describe the properties of physical systems. Certain books add that, to be useful, the thermodynamic potentials must be expressed in their “natural variables”. Here we show that, given a set of physical variables, an appropriate thermodynamic potential can always be defined, which contains all the thermodynamic information about the system. We adopt various perspectives to discuss this point, which to the best of our knowledge has not been clearly presented in the literature.

摘要 现有多数热力学专著均会阐释热力学势（thermodynamic potential）的定义，以及其在描述物理系统性质时的便捷性。部分著作还补充说明，热力学势若要具备实用价值，必须以其「自然变量」形式进行表述。本文证明：只要给定一组物理变量，总能定义出适用于该组变量的热力学势，且该势可完整涵盖系统的全部热力学信息。本文从多个视角对该观点展开论述——据我们所知，此前相关文献尚未对该内容作出清晰阐释。