Electronic structure of perovskite LaMnO3 and CaMnO3

Perovskite structured lanthanum manganite (LaMnO3) can be made to exhibit both strong ferromagnetism and metallic conductivity by partial substitution of La ions (3+ valence) with 2+ valence ions such as Ca. The electronic structures of LaMnO3 and CaMnO3 were calculated using Hartree Fock-linear combination of atomic orbitals (LCAO) and Local Density-Molecular Dynamics programs. The band structure show that both are isolators. The valence energy bands are highly degenerated at Γ point in reciprocal space for LaMnO3. The conduction bands are partly degenerated in both structures. The dispersion of valence band of LaMnO3 is about 1.7 eV and the dispersion of conduction band is about 2.0 eV from Γ point to M point. The top two valence bonds of CaMnO3 are quite flat. The conduction band disperse down significantly, this behaviour could give some reasons why Ca doped LaMnO3 is metallic conductor. The energy gap was obtained but overestimated as expected. The total density of states was found and compared with experimental results. The electronic images show that the interactions between Mn, Ca and three O are stronger than that between La and O. The bonding of Mn-O is pdσ bond