"Overlap" Contributions to the Electric-Field-Gradient Components at theFe3+Site in FeOCl

Abstract

Using the simple Sawatzky model, we have made an evaluation of the "overlap" contributions to the electric-field-gradient (EFG) components at the non-axially-symmetric ${\mathrm{Fe}}^{3+}$ site in FeOCl. The modifications to the EFG components calculated previously by lattice-sum methods are considerable. For ${\mathrm{O}}^{2-}$ and ${\mathrm{Cl}}^{-}$ polarizibility $\alpha$ values of 1.0 ${\mathrm{\AA }}^3$, it was possible both to match the experimental asymmetry parameter $\eta$ value of 0.32 and to get a $Q\left({\mathrm{Fe}}^{57m}\right)$ value of 0.19 b, close to the ferrous consensus.