Point charge model analysis of the quadrupole splitting in normal spinels

The point charge model analysis was used to gain a clear understanding of the primary contributions to the quadrupole splitting (Δ) in the normal spinels ZnFe₂O₄ and CdFe₂O₄. The large difference in Δ between zinc and cadmium ferrite is not able to be explained using a monopole/dipole model based solely on their varying lattice constants and oxygen parameters. It is suggested that a modification of the effective charges within each crystal and/or a subtle twisting of the oxygen sub-lattice is required to accurately predict Δ in these spinels.