A comparative study of Birch and Kumar equations of state under high pressure - NaCl as an example

A comparative study of the Birch and Kumar equations of state is presented to demonstrate their validity for a wide range of pressure, viz, from atmospheric pressure up to the structural transition pressure. It is found that these equations of state are equally good in the low pressure range and deviations occur under the effect of high pressures. The comparison demonstrates that the results obtained by the Kumar equation of state are in better agreement with the experimental data as compared with the Birch equation of state. The application of Kumar's equation of state is also discussed at high temperatures, viz. from room temperature up to the melting temperature. The good agreement between theory and experiment demonstrates the validity of the Kumar equation of state recently proposed for the entire range of pressure and temperature.