Crystal Field in Rare-Earth Trichlorides. V. Estimation of Ligand–Ligand Overlap Effects

Ab initio calculations of certain ligand–ligand overlap contributions to the crystal field in the complex (PrCl₉)⁶⁻ are described. Estimates are made of those terms which have not been calculated directly. Contributions of third order in the overlap integrals are shown to be about 15% of the total $\text{n\hspace{0.17em}=\hspace{0.17em}6}$ crystal field parameters for this complex and thus provide an effective limitation to the use of the superposition approximation in analyzing experimental data.