Vibrational spectrum of A1B3O2 and AIBIIIO2 compounds with the rhombohedral α-NaFeO2 structure

The Raman and i.r. spectra of AIBIIIX2 (X = O or S) compounds with the α-NaFeO2 rhombohedral structure are reported and discussed on the basis of a group theoretical analysis. Most of the sulfur compounds exhibit the two predicted Raman-active frequencies; they are shown to be independent of the mass of both AI and BIII cations and correspond to motions of the anionic lattice. The origin of the 4 i.r. active fundamentals is more complex. The relative influence of AI, BIII and X on these frequencies is discussed on the basis of appropriate experimental data. © 1972.