Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Sugahara, M. Articles by Ohtaka, O. GeoRef GeoRef Citation

Single-crystal X-ray diffraction study of CaIrO₃

¹ Graduate School of Science, Kumamoto University, Kumamoto 860-8555, Japan
² Institute for Study of the Earth’s Interior, Okayama University, Misasa 682-0193, Japan
³ Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8502, Japan
⁴ Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
⁵ Graduate School Science and Engineering, Yamaguchi University, Ube 755-8611, Japan

Correspondence: ^* E-mail: blackherejp{at}yahoo.co.jp

Single crystals of CaIrO₃ were prepared via flux growth method. Crystal structure parameters, including the anisotropic displacement parameters, are determined based on a single-crystal X-ray diffraction experiment. The unit-cell dimensions are a = 3.147(2), b = 9.866(6), and c = 7.302(5) Å. The structure is a three-dimensional dense structure with small vacant spaces. The CaIrO₃ structure can be described as a pseudo-one-dimensional oxide and is compared with Ca₄IrO₆ structure. The IrO₆ octahedra are significantly distorted, in contrast to other octahedral Ir⁴⁺ compounds. The O-O distances for faces and edges shared between polyhedra are shorter than other non-shared edge distances. These effects are explained by Pauling’s rules and occur to decrease the repulsion between the cations. Thermal vibrations of Ca and Ir atoms are significantly anisotropic. Thermal vibrations of Ca and Ir atoms are restricted in orientation toward the shared face, shared edges, and shortest cation-cation directions. The single-crystal experiment shows that CaIrO₃ crystals grow fastest along the a axis and that they assume a prism or needle shape. Strongly preferred orientation of such prism shaped CaIrO₃-type post perovskite MgSiO₃ crystals may develop under the shear flow in the Earth’s mantle.

Key Words: Post-perovskite • CaIrO₃ • single crystal • X-ray diffraction • lower mantle • D’ layer