School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
Nat Commun. 2013;4:2331. doi: 10.1038/ncomms3331.
Since their discovery in 1822, supercritical fluids have been of enduring interest and have started to be deployed in many important applications. Theoretical understanding of the supercritical state is lacking and is seen to limit further industrial deployment. Here we study thermodynamic properties of the supercritical state and discover that specific heat shows a crossover between two different regimes, an unexpected result in view of currently perceived homogeneity of supercritical state in terms of physical properties. We subsequently formulate a theory of system thermodynamics above the crossover, and find good agreement between calculated and experimental specific heat with no free-fitting parameters. In this theory, energy and heat capacity are governed by the minimal length of the longitudinal mode in the system only, and do not explicitly depend on system-specific structure and interactions. We derive a power law and analyse supercritical scaling exponents in the system above the Frenkel line.
自 1822 年被发现以来，超临界流体一直引起人们的持久兴趣，并开始在许多重要的应用中得到应用。对超临界状态的理论理解是缺乏的，这被认为限制了进一步的工业应用。在这里，我们研究了超临界状态的热力学性质，发现比热显示出两种不同模式之间的交叉，这是一个出人意料的结果，因为目前认为超临界状态在物理性质方面是同质的。随后，我们制定了一个超越交叉点的系统热力学理论，并发现计算出的比热与实验结果吻合良好，没有自由拟合参数。在这个理论中，能量和热容量只受系统中纵向模式的最小长度的控制，而不明确地依赖于系统特定的结构和相互作用。我们推导了一个幂律，并分析了弗伦克尔线以上系统中的超临界标度指数。
