Thermoelastic properties of CaO under high hydrostatic pressure using equations of state

Using four equations of state: Vinet EOS, Birch Murnaghan EOS, Bardeen EOS, and Brennan Stacey EOS, under high pressure and ambient temperature. This study investigates the thermoelastic characteristics of B1-CaO material, including Debye temperature, compression ratio, lattice constant, Grüneisen parameter, and isothermal bulk modulus. Calcium oxide (CaO) was selected due to its fundamental role in geophysics, materials science, and high-pressure research, particularly in understanding oxides behavior in extreme environments. The experiment showed a decrease in compression ratio with increasing expanding pressure, a finding consistent with previous EOS data, especially at pressures below 45 GPa. The isothermal bulk modulus increases with pressure, though a divergence appears between experimental data and the (B-M EOS, Vinet EOS, and Bardeen EOS) beyond 30 GPa. The thermal expansion coefficient of CaO decreases with pressure, becoming pressure-independent at high pressures. Lattice constant and Grüneisen parameter decline with pressure, highlighting atomic compression's impact on CaO's vibrational properties.