Effects of Ba substitution on stability and electronic structure of perovskite CaMnO₃ oxide

The stability and electronic structure of the heavy element Ba substituted perovskite type oxide CaMnO₃ have been studied by the psudo-potential approximation density functional theory calculation method. The results show that the lattice distortion has been induced by Ba substitution and the distortion is anisotropic. The Ba substituted perovskite type oxide CaMnO₃ exhibits semiconductor character and the stability decreases. The indirect band gap has been remained by Ba substitution for Ca site for the perovskite type oxide CaMnO₃ yet, the band gaps of the spin up electrons and the spin down electrons have been slightly decreased to 0.659 eV and 0.655 eV, respectively. The semiconductor to conductor transition has also been found. The electrons of the Ba substituted perovskite type oxide CaMnO₃ form energy bands near -37.5 eV, -18 eV, -16 eV, -5 eV ∼ 0 eV and 1 eV, and the peak values of the density of states curve decreases along with the energy regions of -18 eV, -16 eV and -0.7 eV. The dispersion characters of the bands within the valance bands and the conduction bands are much different, which indicate their diverse effective mass. The Mn p, O p and the Mn d electrons have contribution to the density of states at the Fermi level, these electrons determine the conduction process of the titled oxide materials. (authors)