Ab initio calculations of the thermodynamic parameters of lithium, sodium, and potassium oxides under pressure

Abstract

The parameters of the equation of state and Gruneisen parameters for lithium, sodium, and potassium oxides have been calculated in the generalized gradient approximation of the density functional theory using a linear combination of atomic orbitals with the CRYSTAL09 software package. The frequencies of long-wavelength normal mode vibrations have also been calculated and the dependence of these frequencies on the pressure has been established. The Debye temperature has been determined from the elastic characteristics of the compounds. The dependences of the Debye temperature, compressibility, thermodynamic potential, entropy, specific heat, thermal expansion coefficient, and thermal conductivity coefficient on the pressure in the range from −3 to −15 GPa and on the temperature have been calculated in the quasi-harmonic Debye model. The results obtained are in satisfactory agreement with the available reference and experimental data.