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Flexibility of Hydrogen Bond and Lowering of Symmetry in Proton Conductor
Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
Faculty of Science & Engineering, Setsunan University, Ikeda-Nakamachi, Neyagawa, Osaka 572-8508, Japan
* Author to whom correspondence should be addressed.
Received: 3 July 2012; in revised form: 31 July 2012 / Accepted: 10 August 2012 / Published: 23 August 2012
Abstract: In order to investigate why crystal symmetry lowers with increasing temperature by phase transition of TII–III (=369 K) in Cs3H(SeO4)2, in spite of the fact that crystal symmetry in the high-temperature phase of many ionic conductors becomes higher by the phase transition, we have studied the relation between the change in crystal symmetry and the appearance of proton motion. It was found from the analysis of domains based on crystal structure that the number of possible geometrical arrangement of hydrogen bond in phase II becomes two times larger than that in phase III, derived from the lowering of crystal symmetry with increasing temperature. These results indicate that the lowering of crystal symmetry in phase II appears by the increase of the number of geometrical arrangements and by the enhancement of the flexibility of hydrogen bond. Considering that the enhancement of the flexibility of hydrogen bond yields mobile proton in phase II, it is deduced that mobile proton in phase II appears in exchange for the lowering of crystal symmetry at II–III phase transition.
Keywords: phase transition; ionic conductor; hydrogen-bonded compound; ferroelasticity
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Yoshida, Y.; Hatori, J.; Kawakami, H.; Matsuo, Y.; Ikehata, S. Flexibility of Hydrogen Bond and Lowering of Symmetry in Proton Conductor. Symmetry 2012, 4, 507-516.
Yoshida Y, Hatori J, Kawakami H, Matsuo Y, Ikehata S. Flexibility of Hydrogen Bond and Lowering of Symmetry in Proton Conductor. Symmetry. 2012; 4(3):507-516.
Yoshida, Yukihiko; Hatori, Junko; Kawakami, Hinako; Matsuo, Yasumitsu; Ikehata, Seiichiro. 2012. "Flexibility of Hydrogen Bond and Lowering of Symmetry in Proton Conductor." Symmetry 4, no. 3: 507-516.