Electron Density Study of Garnets:Z3Al2Si3O12(Z=Mg, Fe, Mn, Ca) and Ca3Fe2Si3O12

The crystal structures of seven crystals from five garnet mineral species have been studied through single-crystal X-ray diffraction methods incorporating scattering factor refinement procedures. The derived experimental scattering factors for each atomic species show similar scattering-angle-dependent patterns in their deviations from the theoretical factors. The Si–O distances remain virtually unchanged in the Ca garnets even though the cell constants and the other cation–oxygen distances change with composition. Electron density residuals indicating bonding electrons are seen in all seven crystals, with ~0.2 e/?3height between Si and oxygen. Two crystals containing divalent Fe show a characteristic electron density deformation indicating the orientation of thedorbital with paired electrons