ANALYSIS OF PRESSURE-VOLUME RELATIONS FOR NACL CRYSTAL AT HIGH-TEMPERATURES

Some of the most widely used phenomenological forms of equation of sta te, viz. Murnaghan equation of state, the Birch equation of state and the universal equation of state, are modified by taking into account t he effect of thermal pressure. The variation of the product of thermal expansion coefficient a and the isothermal bulk modulus;BT With volum e is estimated using the thermodynamic relations investigated recently . The modified forms of equation of state are used to obtain P-V-T rel ations for NaCl crystal up to a pressure of 35 kbar and in the tempera ture range 298-773 K. The results are found to present reasonably good agreement with experimental data.