Electronic structure of the perovskite oxides: La1-xCaxMnO3

The electronic structures of the perovskite oxides, LaMnO3 and CaMnO3, are studied using density-functional methods. Antiferromagnetic insulating (AFI) solutions are obtained for both compounds within the local-density approximation (LDA). For LaMnO3 the Jahn-Teller distortion, found necessary for the AFI solution, produces occupied Mn(z(2) - 1) orbitals pointed along the long, basal-plane Mn-O bonds. The large on-site Coulomb U and exchange J, obtained from ''constrained'' LDA calculations, U approximate to 8-10 eV and J approximate to 0.9 eV, indicate important correlation effects and yield large redistribution of the spectral weight within the LDA + U approach.