Theoretical analysis of the ligand field spectrum of K 3CoF 6

Abstract

We present a detailed ab initio study of the ligand field spectrum of the CoF 3− 6 cluster in the K 3CoF 6 crystal. The crystal environment around the octahedral CoF 3− 6 cluster is accounted for by a Madelung potential. The ground and ligand field excited states of K 3CoF 6 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 CASSF level while the spin-forbidden quintet-triplet transitions require the inclusion of dynamical correlation.