t2gversus all 3dlocalization in LaMO3

Using the LDA+U method (where LDA is local-density approximation) we show that a separate treatment of ${\mathit{t}}_{2\mathit{g}}$ and ${\mathit{e}}_{\mathit{g}}$ electrons on transition-metal sites as localized and itinerant, respectively, gives an appropriate description for the band structure of LaM${\mathrm{O}}_{3}$ perovskites (M=Ti--Cu) and systematically improves results of the local-spin-density approximation (LSDA) for the ground-state and single-electron excited-state properties. The analysis is based on comparison with experimental magnetic, optical, and photoemission data. Parameters of the effective Coulomb interaction estimated for ${\mathit{t}}_{2\mathit{g}}$ electrons and a role of ${\mathit{e}}_{\mathit{g}}$ screening are discussed. The present approach accounts well for the insulating natures of ${\mathrm{LaTiO}}_{3}$, ${\mathrm{LaVO}}_{3}$, and ${\mathrm{LaCoO}}_{3}$, for which the LSDA predicts metallic states. Changes of the LSDA band structure for ${\mathrm{LaMnO}}_{3}$ and ${\mathrm{LaNiO}}_{3}$ are almost negligible due to the very efficient screening of on-site ${\mathit{t}}_{2\mathit{g}}$ interactions by ${\mathit{e}}_{\mathit{g}}$ electrons. \textcopyright{} 1996 The American Physical Society.