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 insul ating (AFI) solutions are obtained for both compounds within the local -density approximation (LDA). For LaMnO3 the Jahn-Teller distortion, f ound necessary for the AFI solution, produces occupied Mn(z(2) - 1) or bitals pointed along the long, basal-plane Mn-O bonds. The large on-si te Coulomb U and exchange J, obtained from ''constrained'' LDA calcula tions, U approximate to 8-10 eV and J approximate to 0.9 eV, indicate important correlation effects and yield large redistribution of the sp ectral weight within the LDA + U approach.