Crystal-field polarization and the insulating gap in FeO, CoO, NiO, andLa2CuO4

An orbital polarization correction to local spin density (LSD) theory is developed in a crystal field basis, and applied to FeO, CoO, NiO, and ${\mathrm{La}}_2$ ${\mathrm{CuO}}_4$. The result is a substantial enhancement of the LSD band gap for NiO, and the creation of an insulating ground state for FeO, CoO, and ${\mathrm{La}}_2$ ${\mathrm{CuO}}_4$.