Chemical Physics Letters vol:224 issue:1-2 pages:207-212
We present a detailed ab initio study of the ligand field spectrum of the CoF63- cluster in the K3CoF6 crystal. The crystal environment around the octahedral CoF63- cluster is accounted for by a Madelung potential. The ground and ligand field excited states of K3CoF6 have been studied with the inclusion of correlation effects. Each state was first optimized separately in a complete active space self-consistent field (CASSCF) calculation, including ten active electrons occupying the bonding e(g) and anti-bonding e(g)* and t(2g)* shells. Further correlation was incorporated by using the averaged coupled pair functional approach (ACPF) with the CASSCF configuration space as reference space and where the maximum number of correlated electrons was up to twenty. The one quintet-quintet transition is already described well at the CASSCF level while the spin-forbidden quintet-triplet transitions require the inclusion of dynamical correlation.