Two innovative equivalent statements of the third law of thermodynamics

• Published in: Chinese physics B Vol. 33; no. 6; pp. 60504 - 327
• Main Authors: Chen, Xiaohang, Zhou, Yinghui, Chen, Jincan
• Format: Journal Article
• Language: English
• Published: Chinese Physical Society and IOP Publishing Ltd 01.06.2024
• Subjects: absolute zero temperature; heat capacity statement; Nernst statement; Nernst theorem; the third law of thermodynamics; Nernst theorem; the third law of thermodynamics; heat capacity statement; Nernst statement; absolute zero temperature
• ISSN: 1674-1056; 2058-3834
• DOI: 10.1088/1674-1056/ad39c8

It is found from textbooks and literature that there are three different statements for the third law of thermodynamics, i.e., the Nernst theorem, the unattainability statement of absolute zero temperature, and the heat capacity statement. It is pointed out that such three statements correspond to three thermodynamic parameters, which are, respectively, the entropy, temperature, and heat capacity, and can be obtained by extrapolating the experimental results of different parameters at ultra-low temperatures to absolute zero. It is expounded that because there is no need for additional assumptions in the derivation of the Nernst equation, the Nernst theorem should be renamed as the Nernst statement. Moreover, it is proved that both the Nernst statement and the heat capacity statement are mutually deducible and equivalent, while the unattainability of absolute zero temperature is only a corollary of the Nernst statement or the heat capacity statement so that it is unsuitably referred to as one statement of the third law of thermodynamics. The conclusion is that the Nernst statement and the heat capacity statement are two equivalent statements of the third law of thermodynamics.