New insights into the effects of covalency on the ligand field parameters: a DFT study

A new, non-empirical, DFT based ligand field (LF) model is proposed. The calculation involves two steps: (i) an average of configuration (AOC), with equal occupation of the d-orbitals is carried out, (ii) with these Kohn–Sham orbitals kept frozen, the energies of all single determinants (SD) within the whole LF-manyfold is performed. These energies are then used to estimate all the Racah- and LF-parameters needed in a conventional LF-calculation. The results of this first-principle prediction are in very good agreement with the experimental values. Test calculation of tetrahedral Cr(IV) and Ni(II) complexes are used to validate the new model and to analyze the parameters of the LF.