OM4 TETRAHEDRA LINKAGES AND CATIONIC GROUP (MO)NN+ IN RARE EARTH OXIDES AND OXYSALTS

Consideration of the coordination of the oxygen atoms in rare-earth oxide and oxysalt structures shows that these are generally surrounded by a tetrahedron of metal atoms. All known structures can therefore be described as tri-dimensional or bi-dimensional packing of such OM4 tetrahedra sharing edges. In A-M2O3, B-M2O3, and the oxysalts, the packed tetrahedra appear as an infinite polymeric complex cation (MO)nn+. Possible implications for the unknown structures of nonstoichiometric oxides are discussed. The results suggest that the oxygen atoms are involved in a directional bonding. © 1968.