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'81 Br NQR' in keywords Facet   Publication Year 1996  [X]
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1Author    Tsutomu Okuda, Shusaku Gotou, Toshirou Takahashi, Hiromitsu Terao, Koji YamadaRequires cookie*
 Title    Structure and Successive Phase Transitions of RGeBr 3 (R = Alkylammonium) Studied by Means of NQR  
 Abstract    A series of tribromogermanate(II) complexes RGeBr 3 (R = CH 3 NH 3 , (CH 3) 2 NH 2 , (CH 3) 4 N, C 2 H 5 NH 3 , (C 2 H 5) 4 N) have been synthesized and characterized by 81 Br NQR, AC conductivity, DTA, and X-rax diffraction. These measurements revealed the presence of successive phase transi-tions in these complexes. The crystal structures of Phases I and II in (NH 3) 4 NGeBr 3 were derived from the Rietveld analysis of powder X-ray diffraction. The electric conductivity was considerably high in CH 3 NH 3 GeBr 3 and (NH 3) 4 NGeBr 3 . The conduction mechanism is discussed on the basis of 81 Br NQR spin-lattice relaxation times and crystal structures. 
  Reference    Z. Naturforsch. 51a, 686—692 (1996); received October 10 1995 
  Published    1996 
  Keywords    81 Br NQR, T x, Phase Transition, Ionic Motion, Ionic Conductivity 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0686.pdf 
 Identifier    ZNA-1996-51a-0686 
 Volume    51 
2Author    K. Yamada, T. Ohtani, S. Shirakawa, H. Ohki, T. Okuda, T. Kamiyama, K. OikawaRequires cookie*
 Title    Phase Transition of C 5 H 5 NHSbBr 4 Having a Hypervalent Bond: A 2 H NMR and X-Ray Diffraction Study* [Phase Transition of C 5 H 5 NHSbBr 4 l  
 Abstract    The second order phase transition at 253 K of pyridinium tetrabromoantimonate(III), C 5 H 5 NHSbBr 4 , has been characterized by means of X-ray diffraction and 2 H NMR. As was suggested from the 81 Br NQR spectra, the Rietveld refinements of the X-ray diffraction patterns at 297 K and 116 K confirm the structural change of the anion from SbBr 4 to SbBr 3 • Br -. The line shape analysis of the 2 H NMR using the deuterated analog revealed that the librational amplitude of the pyridinium ring about the axis normal to the plane increased with temperature and its rms amplitude reaching ca. 25° at T c . The librational motion may induce the phase transition breaking the hydrogen bonds of the type N-H -Br. However, nearest-neighbor 2n/6 jump or reorientation such as seen in benzene were not observed even at 350 K. 
  Reference    Z. Naturforsch. 51a, 739—744 (1996); received October 11 1995 
  Published    1996 
  Keywords    2 H NMR, 81 Br NQR, Rietveld analysis, Phase transition, Hypervalent bond 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0739.pdf 
 Identifier    ZNA-1996-51a-0739 
 Volume    51