Comment on “A new equation of state based on Grover, Getting and Kennedy’s empirical relation between volume and bulk modulus. The high pressure thermodynamics of MgO ” by M. H. G. Jacobs and H. A. J. Oonk, Phys. Chem. Chem. Phys., 2000, 2, 2641

Abstract

This Comment discusses certain interesting implications of the new equation of state (EoS) proposed recently by Jacobs and Oonk (Phys. Chem. Chem. Phys., 2000, 2, 2641). In essence, the physical significance of the temperature independent thermoelastic parameter ‘ b’ appearing in their key equation is clarified by relating it to the more popular isothermal Anderson–Grüneisen parameter (δ_T). A novel quantification of the isobaric temperature dependence of δ_T is also established in this way. The similarity of the Jacobs–Oonk relation to the one proposed earlier by Tallon (J. Phys. Chem. Solids, 1980, 41, 837) is also pointed out. In addition it is shown that the validity of the Jacobs–Oonk relation for the temperature dependence of bulk modulus implies that the product of isothermal bulk modulus (B_T) and thermal expansivity (α_V) is temperature independent. Further, it also leads to an exponential scaling for the isothermal volume dependence of thermal expansivity.