DENSITY-FUNCTIONAL THEORY AND STRONG-INTERACTIONS - ORBITAL ORDERING IN MOTT-HUBBARD INSULATORS

Evidence is presented that within the density-functional theory orbital polarization has to be treated on an equal footing with spin polarization and charge density for strongly interacting electron systems. Using a basis-set independent generalization of the LDA+U functional, we show that electronic orbital ordering is a necessary condition to obtain the correct crystal structure and parameters of the exchange interaction for the Mott-Hubbard insulator KCuF3.