First-principles calculations of the electronic structure and spectra of strongly correlated systems: the LDA+ U method

A generalization of the local density approximation (LDA) method for systems with strong Coulomb correlations is described which gives a correct description of the Mott insulators. The LDA+U method takes into account orbital dependence of the Coulomb and exchange interactions which is absent in the LDA. The scheme can be regarded as a `first-principles' method because there are no adjustable parameters. When applied to the transition metal and rare-earth metal compounds, the LDA+U method gives a qualitative improvement compared with the LDA not only for excited-state properties such as energy gaps but also for ground-state properties such as magnetic moments and interatomic exchange parameters. The orbital-dependent rotationally invariant LDA+U potential gives a correct orbital polarization and a corresponding Jahn - Teller distortion as well as polaron formation.