Analysis based on equation of state for sodium halides Original Research Article

The modification in the Shanker formulation by Kumar and Kumar (J. Phys. Chem. Sol. 68 (2007) 670) for describing high-pressure behaviour of sodium halides has been shown here to be mathematically inconsistent. It has been emphasized in the present study that the correct way of describing the equation of state is based on the thermodynamics of solids in the limit of infinite pressure as formulated by Stacey. The pressure–volume relationships for NaF, NaCl, NaBr and NaI determined from the Stacey equations are found to present good agreement with experimental data. The ratio View the MathML sourceK∞′/K0′=3/5 predicted empirically from the geophysical data by Stacey makes his equations quite powerful as they become usable with one lesser fitted parameter.