NaIrO3 - A pentavalent post-perovskite

Sodium iridium(V) oxide, NaIrO3, was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO3, the much-studied structural analogue of the high-pressure post-perovskite phase of MgSiO3. Among the oxide post-perovskites, NaIrO3 is the first example with a pentavalent cation. The structure consists of layers of corner- and edge-sharing IrO6 octahedra separated by layers of NaO8 bicapped trigonal prisms. NaIrO3 shows no magnetic ordering and resistivity measurements show non-metallic behavior. The crystal structure, electrical and magnetic properties are discussed and compared to known post-perovskites and pentavalent perovskite metal oxides.Comment: 22 pages, 5 figures. Submitted to Journal of Solid State Chemistr

Ab initio investigation of perovskite and post-perovskite CaPtO3

For the recently synthesized post-perovskite (PPV) CaPtO3 we investigate the electronic band structure properties in connection with hypothetical perovskite PV–CaPtO3 within density functional theory using pseudo-potential and all electron methods. Both systems are found insulating in agreement with a tetravalent Pt(IV) low spin d6 state. The equilibrium values of the volume and energy point to a stabilization of the PPV versus PV oxide with a smaller volume in agreement with other homologue systems within Earth lower mantle such as PPV–MgSiO3. This is also addressed from the analysis of the chemical bonding focusing on the change of the Pt–O bonding upon going from PV and PPV systems whereby the covalent Pt–O bonds are differentiated and reinforced within PPV system with respect to PV