Phonons and thermal properties of α-, β-, δ-, and κ-Ga2O3 polymorphs from first principles studies

The influence of Ga2O3 polymorphism on lattice vibrations and the temperature dependence of thermodynamic properties is investigated within the framework of density functional theory, employing an exchange-correlation functional with generalized gradient corrections. The atomic structures and binding energies of four polymorphs are predicted, along with their energetic stability and pressure dependence. The dynamic stability of α-, β-, δ-, and κ-Ga2O3 is assessed through the dispersion of acoustic phonon branches. Phonon band structures and densities of states are computed to analyze their effects on thermodynamic properties and heat capacity as a function of temperature. The results, including Debye temperatures, are compared with other ab initio calculations and experimental data.