Crystal structure and properties of barium thorate BaThO$_3$ from first principles

Abstract

The phonon spectrum of cubic BaThO$_3$ with the perovskite structure is calculated from first principles within the density functional theory. The analysis of unstable modes in the phonon spectrum enables to determine the symmetry of all possible distorted phases, calculate their energies, and show that the ground-state structure of barium thorate is $Pbnm$. For this structure, the static and optical dielectric constants, elastic moduli, heat capacity, Raman spectra, and the energy band gap in the LDA and $GW$ approximations are calculated. The possibility of the structural phase transitions in BaThO$_3$ is also discussed.