Thermodynamic properties of NaCl on its P-V-T surface

Abstract

Various state equations derived by expanding energy as function of volume in a Taylor series and using the difference order Pade approximants have been combined with the quasi-harmonic approximation for free energy to reproduce the thermodynamic properties of the crystal on its P-V-T surface. The authors have used these state equations to compute the pressure-volume behaviour, the isothermal bulk modulus, the pressure derivative of bulk modulus and the Anderson-Gruneisen parameter of NaCl at high pressure (up to 80 kbar) and various temperatures (T=298, 550 and 800K). The results obtained are reasonably good, lending support to the state equations and the method used to extend their applicability at elevated temperatures. The significant results obtained in the present study include the unified reduced equation of state for NaCl which generates a single curve for the P-V behaviour at all temperatures.