Vibrational Spectroscopic Studies of Layered Silicates

The FT-IR and FT-Raman spectra of three-layered silicates, magadiite, kenyaite, and ilerite have been measured. The correlation between vibrational spectra and the structural properties of silicates under investigation has been made. The unit cells of all three silicates appear to be centrosymmetric since the mutual exclusion rule applies. The factor group symmetries of magadiite and ilerite may be C2h. The unit cell symmetry of kenyaite is either C4h or D4h. All three silicates have multilayer structures with five- and six-membered rings. For magadiite and kenyaite, some Si−O−Si linkages with very large bond angles near 180° may exist. Hydrogen bonding occurs in all three silicates, but not all of the hydroxyl groups are involved. The structure of ilerite may not be related to those of magadiite and kenyaite as closely as previously thought since its vibrational spectra are distinctly different from those of magadiite and kenyaite in many aspects.