Properties of Materials at High Pressures and High Tempratures Using the Stacey Reciprocal K Primed Equation of State

Abstract

newline We have pointed out the constraints required for an equation of state (EOS) to be newlinephysically acceptable and universally applicable for the entire range of compressions for a newlinematerial at high pressures. We have discussed the boundary conditions valid at zero pressure newlineand infinite pressure. The concept of infinite pressure behavior has been discussed. It has been newlineemphasized that the Stacey reciprocal K- primed EOS satisfies the entire necessary criterion newlinefor the validity of EOS. On the other hand, equations of state reported previously do not newlinesatisfy the condition of physical acceptability of an equation of state. newlineIn this study, we used the Stacey reciprocal K-primed EOS to determine the newlinerelationships with pressure, volume, and temperature for NaCl up to a temperature of 900K newlineand pressure of 25 GPa. The bulk modulus values and pressure derivative (PD) were also newlineobtained for the entire range of temperatures and pressures considered in this study. We newlineinvestigated the thermoelastic properties of NaCl at high temperatures and high pressures newlineusing the results based on the EOS. The pressure dependences of the thermal expansivity and newlineGrüneisen parameter were both determined using the formulations, which satisfied the newlinethermodynamic constraints at infinite pressure. The values of the higher-order Grüneisen newlineparameters were obtained upto fourth order for NaCl at high pressures. The thermal newlineexpansivity values for NaCl at high pressures and high temperatures were calculated using the newlineAnderson-Grüneisen formulation. The results obtained using the two methods were compared newlineand discussed. The Grüneisen parameter values determined at different pressures were used to newlinepredict the melting curve for NaCl. The melting temperatures obtained at different pressures newlineusing the Lindemann-Gilvarry law agreed with the experimental data within 10 %. newlineWe have obtained volume dependence of the Grüneisen parameter for MgO and hcp newlineiron using the formulations due to Stacey and Davis based on the third-order ofGrüneisen newlineparameter. Values of higher order of Grüneisen parameters up to fourth order have also been newlineobtained with the help of the Shanker reciprocal gamma relationship satisfying the newlinethermodynamic constraints at extreme compression in the limit of infinite pressure(LOIP). newlineThe results obtained from the Stacey-Davisformulation present close agreement with those newlinedetermined from the Shanker formulation. newlineix