Ab initio SCF and limited CI calculations of the d-d transitions in cobalt oxide

Ab initio calculations using an extended set of gaussian-type orbitals have been performed for the CoO₆ ^10- cluster in the Hartree-Fock approximation and with a limited configuration interaction. The results have been compared with those of crystal-field theory. CoO is found to be a very ionic system with localized d-electrons. The excited d-states may be described using a simple configuration interaction scheme, which is found to be almost equivalent to a crystal-field parameterized configuration interaction built on Hartree-Fock results. Localization and delocalization phenomena in openshell systems have been discussed.