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1998 (1)
1996 (1)
1Author    Hiromitsu Terao, Tsutomu Okuda, Sachiyo Uyama, Hisao Negita, Shi-Qi Dou, Hartmut Fuess, Alarich WeissRequires cookie*
 Title    Crystal Structure Refinement and Single Crystal 81 Br Zeeman NQR Study of KHgBr 3 H 2 0  
 Abstract    Three 81 Br NQR resonance lines of KHgBr 3 H 2 0 were detected between 77 K and room temperature. From the Zeeman effect measurement on a single crystal the nuclear quadrupole coupling constants (e 2 qQ/h) and the asymmetry parameters (r/) were obtained, which are 228.42 MHz and 0.005, 226.24 MHz and 0.005, and 108.76 MHz and 0.465 for e'qQIh and rj at 295 K, respectively. Large deviations of the observed directions of electric field gradient tensors from the directions expected from previous X-ray results have been found. With the present X-ray redetermination, 1 Br NQR and structure are in good agreement. The structure and bonding in the compound are discussed. 
  Reference    Z. Naturforsch. 51a, 1197—1202 (1996); received June 14 1996 
  Published    1996 
  Keywords    KHgBr v H 2 0, X-Ray analysis, NQR, Crystal structure, Chemical bonding 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-1197.pdf 
 Identifier    ZNA-1996-51a-1197 
 Volume    51 
2Author    Hiromitsu Terao, Masao Hashimoto\, Tsutomu Okuda, Alarich WeissRequires 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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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0559.pdf 
 Identifier    ZNA-1998-53a-0559 
 Volume    53