Loci of extrema of thermodynamic response functions for the Lennard–Jones fluid

Abstract

Lines of extrema along isotherms and isobars for the residual isochoric heat capacity, the residual isobaric heat capacity, the isobaric thermal expansivity, and the isothermal compressibility of the Lennard–Jones fluid have been studied from popular equations of state due to Johnson et al. [Mol. Phys. 78, 591 (1993)], Kolafa and Nezbeda [Fluid Phase Equilib. 100, 1 (1994)], and Mecke et al. [Int. J. Thermophys. 17, 391 (1996)]. On depicting such loci in the pressure–temperature plane, the characteristic behaviour of thermodynamic response functions in the ideal-gas limit (at high enough temperatures or low enough pressures), the close-packed-fluid limit (at low enough temperatures or high enough pressures) as well as in the liquid, critical, and supercritical regions is identified. The present analysis is informative itself, but it also stimulates further work in order to tackle more complicated cases of study including associated fluids.