Crystal structure of post-perovskite-type Cairo3 reinvestigated: New insights into atomic thermal vibration behaviors

Akihiko Nakatsuka, Kazumasa Sugiyama, Akira Yoneda, Keiko Fujiwara, Akira Yoshiasa

Research output: Contribution to journalArticle

Abstract

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 [010]. Chains formed by edge-sharing of IrO6 octahedra (point-group symmetry 2/m.) run along [100] and are interconnected along [001] 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 [100] and are interconnected along [001] 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 [100], 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.

Original languageEnglish
Pages (from-to)1109-1113
Number of pages5
JournalActa Crystallographica Section E: Crystallographic Communications
Volume71
DOIs
Publication statusPublished - Sep 1 2015

Keywords

  • Calcium iridium(IV) trioxide
  • Crystal structure
  • Post-perovskite
  • Redetermination
  • Thermal vibration

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Materials Science(all)
  • Chemistry(all)

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