Crystal structure of post-perovskite-type CaIrO3 reinvestigated: new insights into atomic thermal vibration behaviors

Acta Crystallographica Section E: Crystallographic Communications

Fujiwara, K.¹  Nakatsuka, A.¹  Yoshiasa, A.²  Sugiyama, K.³  Yoneda, A.⁴ 

[1] Graduate School of Science and Engineering, Yamaguchi University, Ube 755-8611, Japan;Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan;Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan;Institute for Study of the Earth's Interior, Okayama University, Misasa 682-0193, Japan

关键词: CRYSTAL STRUCTURE;    REDETERMINATION;    CALCIUM IRIDIUM(IV) TRIOXIDE;    POST-PEROVSKITE;    THERMAL VIBRATION;   

DOI  :  10.1107/S2056989015015649

学科分类：数学（综合）

来源: International Union of Crystallography

【 摘 要 】

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.

【 授权许可】

CC BY