Single crystals of the title compound, the post-perovskite-type Cairo3 [calcium iridium(IV) trioxide], have been grown from a CaCl2 flux at atmospheric pressure. The crystal structure consists of an alternate stacking of IrO6 octahedral layers and CaO8 hendecahedral layers along . Chains formed by edge-sharing of IrO6 octahedra (point-group symmetry 2/m.) run along  and are interconnected along  by sharing apical O atoms to build up the IrO6 octahedral layers. Chains formed by face-sharing of CaO8 hendecahedra (point-group symmetry m2m) run along  and are interconnected along  by edge-sharing to build up the CaO8 hendecahedral layers. The IrO6 octahedral layers and CaO8 hendecahedral layers are interconnected by sharing edges. The present structure refinement using a high-power X-ray source confirms the atomic positions determined by Hirai et al. (2009) [Z. Kristallogr. 224, 345-350], who had revised our previous report [Sugahara et al. (2008). Am. Mineral. 93, 1148-1152]. However, the displacement ellipsoids of the Ir and Ca atoms based on the present refinement can be approximated as uniaxial ellipsoids elongating along , unlike those reported by Hirai et al. (2009). This suggests that the thermal vibrations of the Ir and Ca atoms are mutually suppressed towards the Ir⋯Ca direction across the shared edge because of the dominant repulsion between the two atoms.
|Number of pages||5|
|Journal||Acta Crystallographica Section E: Crystallographic Communications|
|Publication status||Published - 2015 Sept 1|
- Calcium iridium(IV) trioxide
- Crystal structure
- Thermal vibration