Structural Evolution under Pressure of BiMnO3

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• 作者：Gianluca Calestani ; Fabio Orlandi ; Francesco Mezzadri ; Lara Righi ; Marco Merlini ; Edmondo Gilioli
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：August 18, 2014
• 年：2014
• 卷：53
• 期：16
• 页码：8749-8754
• 全文大小：357K
• ISSN：1520-510X

文摘

The structural behavior of BiMnO₃ under pressure was studied in a quantitative way by single-crystal synchrotron X-ray diffraction up to 36 GPa. Two phase transitions were observed at moderate pressures (1 and 6 GPa, respectively), leading the system at first to the P2₁/c and then to the Pnma symmetry. The breaking of C-centering in the first transition does not affect significantly Jahn鈥揟eller (JT) distortion and orbital order (OO) but determines a significant change in the cooperative tilting of the MnO₆ octahedra. The second transition increases the symmetry to orthorhombic, leading to a Pnma structure similar to the O鈥?structure of LaMnO₃, characterized by a > c > b/鈭?. No symmetry change was observed above 7.1 GPa, but the different compressibility of the lattice parameters (in particular, the b axis) leads at first to a pseudocubic phase (鈮?0 GPa) and then to different parameter ratios (b/鈭? > c > a). Even if the JT distortion is continuously reduced with increasing pressure, it is retained, together with the resulting OO, until the highest measured pressure, pointing out the relevant role of the distortion induced by the Bi³⁺ lone pair in stabilizing the JT distortion.