OM 4 Tetrahedra linkages and the cationic group (M0) n n+ in rare earth oxides and oxysalts

Abstract

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 OM 4 tetrahedra sharing edges. In A-M 2O 3, B-M 2O 3, and the oxysalts, the packed tetrahedra appear as an infinite polymeric complex cation (MO) n n+ . Possible implications for the unknown structures of nonstoichiometric oxides are discussed. The results suggest that the oxygen atoms are involved in a directional bonding.