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Phase transition of pyridinium tetrachloroiodate(III), PyHICl4, studied by a single crystal X-ray analysis and dielectric and heat capacity measurements |
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| Authors: | Tetsuo Asaji Kazuo Eda Toshinobu Adachi Masaharu Oguni |
| Institution: | a Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan b Department of Chemistry, Faculty of Science, Kobe University, Nada-ku, Kobe 657-8501, Japan c Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8551, Japan |
| Abstract: | Change of a local environment of a polar pyridinium ion, which is associated with the phase transition of crystalline pyridinium tetrachloroiodate(III) at Tc = 217 K, was investigated by a single crystal X-ray analysis and dielectric and heat capacity measurements. The site symmetry 2/m of the ion at T > Tc indicates an orientational disorder in the high-temperature phase (HTP). The energy difference ΔE between the stable and meta-stable orientations of the pyridinium ion at the 2/m site was estimated to be ΔE/R ? 560 K at 280 K in the HTP. Below the Tc, an antiferroelectric ordering of the ions was revealed. |
| Keywords: | Phase transition Crystal structure Heat capacity NQR |
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