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Neutron and X-ray scattering studies of structural phase transitions and soft modes in Rb_2ZnBr_4

Journal of physics. Condensed matter Volume 10 Issue 26 Page 5861-5874
published_at 1998
2008010366.pdf
[fulltext] 408 KB
Title
Neutron and X-ray scattering studies of structural phase transitions and soft modes in Rb_2ZnBr_4
Creators Shigematsu H.
Creators Mashiyama H.
Creators Oohara Y.
Creators Ohsima K.
The low-temperature phase transitions of rubidium tetrabromozincate have been investigated with the use of neutron and X-ray scattering techniques to clarify the mechanism of the transitions and to determine the space groups of the low-temperature phases. The low-frequency excitations which soften at the phase transition T_3 = 112 K have been measured by the inelastic neutron scattering technique. On the other hand, no soft phonon mode which makes a contribution to the phase Ⅳ-to-Ⅴ transition at T_4 = 76 K has been observed. Both in phases Ⅳ and Ⅴ, superlatticereflections appear at the position (h)/(2) (k)/(2) (l)/(3), where the Miller indices h, k and l are referred to the lattice constants of phase Ⅰ. In phase Ⅴ, new Bragg reflections emerge at the positon hk0: h + k = 2n + 1 and increase continuously with decreasing temperature. The space groups are considered to be P11b with Z = 24 for phase Ⅳ and C1c1 with Z = 48 for phase Ⅴ according to general group theoretical considerations. Furthermore, structural models for phase Ⅳ are proposed to explain the extra extinction rule, the antiferroelectricity and other observed character of the crystal.
Languages eng
Resource Type journal article
Publishers Institute of Physics
Date Issued 1998
File Version Author’s Original
Access Rights open access
Relations
[ISSN]0953-8984
[NCID]AA10672168
https://doi.org/10.1088/0953-8984/10/26/014
[isPartOf] [URI]http://www.iop.org/EJ/journal/JPhysCM
Schools 大学院理工学研究科(理学)