| | 1 | Author
| Hiromitsu Terao, Masao Hashimoto\, Tsutomu Okuda, Alarich Weiss | Requires cookie* | | | Title
| Phase Transitions and Crystal Structure of Dimethylammonium Tribromomercurate(II), (CH 3 ) 2 NH 2 HgBr 3 , as Studied by 81 Br NQR and Single Crystal X-ray Diffraction  | | | | Abstract
| The temperature dependence of the 81 Br NQR frequencies of the title compound has revealed the presence of three phases (I, II and III, in the order of decreasing temperature): T cl (II -1) = (318 ± 10) K and T c2 (III -II) = (202 ± 1) K. The transitions were confirmed by thermal analysis (DTA). Both of the II-I and I-II transitions exhibited strong hysteresis (/. e., superheating and supercooling, respectively). The crystal data, determined by single crystal X-ray diffraction, are: monoclinic, space group P2/a, a = 1384.8(3), b = 934.7(4), c = 1452.0(2) pm, ß = 104.10(1)°, Z= 8, R = 0.076. The crystal has two crystallographically independent cations (CH 3) 2 NH 2 + and an infinite chain of anions almost in the c-direction. The anion chain is considered to consist of a HgBr 2 molecule and two different HgBr 4 2 ~ anions which are interconnected via weak intermolecular Hg-Br bonds. The splitting patterns of the 8 'Br NQR spectra indicate that rearrangements of the Hg-Br bonds are slight at the III-II transition but serious at the II-I transition. Some of the 81 Br NQR lines show anomalous temperature coefficients, attributable probably to thermal motions of cations. | | | |
Reference
| Z. Naturforsch. 53a, 559—567 (1998); received January 26 1998 | | | |
Published
| 1998 | | | |
Keywords
| (CH 3 ) 2 NH 2 HgBr 3, X-Ray Analysis, NQR, Phase Transition, Crystal Structure | | | |
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| default:Reihe_A/53/ZNA-1998-53a-0559.pdf | | | | Identifier
| ZNA-1998-53a-0559 | | | | Volume
| 53 | |
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