An Investigation of the Equation of State of NaCl at High Pressure by Use of Gordon-Kim Model

Pair-potentials of ions in the NaCl crystal are calculated by using Gordon-Kim model and numerical solutions of Hartree-Fock wave functions for free ions. Results show that short range interactions have different properties for different pairs of ions, the cation-anion pair interaction potential is repulsive, but the cation-cation and anion-anion pair interaction potentials are attractive in the separation range of interest here. Different functional forms of these potentials are adopted and the parameters are determined by the least-square-fit. The Gruneisen parameter and the equation of state of NaCl are calculated by using the theory of lattice dynamics. Agreements between the calculated results and the experimental data are satisfactory.