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1997[X]
1Author    Hiroyuki Ishida, Hiroshi Ono, Ryuichi IkedaRequires cookie*
 Title    Crystal Structure of the High-temperature Solid Phases of Choline Tetrafluoroborate and Iodide  
 Abstract    The crystal structure of the highest-and second highest-temperature solid phases of choline tetrafluoroborate and iodide was determined by X-ray powder diffraction. The structure in the highest-temperature phase of both salts is NaCl-type cubic (a = 10.16(2) Ä, Z = 4 for tetrafluorobo-rate; a = 10.08(2) A, Z = 4 for iodide). The second highest-temperature phase of tetrafluoroborate and iodide is CsCl-type cubic (a = 6.198(6) Ä and Z = 1) and tetragonal (a = 8.706(2) A, c = 6.144(6) Ä, and Z = 2), respectively. DSC was carried out for the iodide, where the presence of three solid-solid phase transitions was confirmed. Enthalpy and entropy changes of these transitions were evaluated. 
  Reference    Z. Naturforsch. 52a, 679—680 (1997); received June 17 1997 
  Published    1997 
  Keywords    Crystal structure, Powder X-ray diffraction, Phase transition 
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 TEI-XML for    default:Reihe_A/52/ZNA-1997-52a-0679_n.pdf 
 Identifier    ZNA-1997-52a-0679_n 
 Volume    52 
2Author    Hiroyuki Ishida, Masakazu Kato, Hiroshi Ono, Ryuichi IkedaRequires cookie*
 Title    Cationic Self-diffusion in Solid Choline Perchlorate Studied by NMR  
 Abstract    The 1 H spin-lattice and spin-spin relaxation times, and the second moment of the 1 H NMR linewidth of choline Perchlorate, [(Cff^NCfFCHiOHJClC^, were measured in its highest-temperature solid phase, i. e. above 275 K. X-ray powder patterns taken at ca. 380 K revealed that in this phase the crystal has a CsCl-type cubic structure (a = 6.326(4) A and Z = 1). From *H NMR experiments it was found that the cations in this phase undergo isotropic rotation and translational self-diffusion. From the 1 H T, measurements, the activation energies of the cationic rotation and self-diffusion were evaluated to be 21.4 ± 0.4 and 62 ± 3 kJ mol -1 , respectively. 
  Reference    Z. Naturforsch. 52a, 637—639 (1997); received May 28 1997 
  Published    1997 
  Keywords    Ionic plastic phase, Self-diffusion, Crystal structure, Nuclear magnetic resonance 
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 TEI-XML for    default:Reihe_A/52/ZNA-1997-52a-0637.pdf 
 Identifier    ZNA-1997-52a-0637 
 Volume    52 
3Author    A. R. Ofial, S.-Q Dou, V. G. Krishnan, H. Paulus, H. Fuess, Al WeissRequires cookie*
 Title    X-Ray and 35 C1 NQR Studies on the Trichloroacetyl Group in Covalent and Ionic Compounds of L-Valine and DL-Valine  
 Abstract    The crystal structures and 35 C1 NQR of trichloroacetyl-DL-valine (1), trichloroacetyl-L-valine (2), as well as the salts of trichloroacetic acid with DL-valine (3) and L-valine (4) have been investigated. Crystal data are for (1): Monoclinic, C2/c, a= 15.835(4) Ä, b= 10.481 (3) Ä, c = 14.046(4) A, /? = 103.28(1), Z = 8; (2): Orthorhombic, P2 1 2 1 2 1 , a = 12.117(3) Ä, 6=10.896(3) Ä, c= 8.718(2) Ä, Z = 4; (3): Triclinic, PI, a= 17.269(3) Ä, 6 = 8.504(3) Ä, c = 10.427(4) A, a = 105.38(2), £ = 96.98(2), y = 96.24(2), Z = 2; (4): Monoclinic, P2 1? a = 10.378(4) A, 6 = 20.349(8) A, c= 11.890(5) A, B = 95.28(2), Z = 8. The onset of rotational motion within the trichloroacetyl groups bleaches out 35 C1 NQR lines between 115 K and 185 K for (l)-(4). While TCA-L-valine (1), TCA-DL-valine (2), and TCA*) • DL-valine (+) (3) do not show any phase transition in the temperature range 77 K to 295 K, TCA <_) • L-valine (+) (4) shows more than one phase transition above 77 K before the three NQR signals bleach out at 164 K. 
  Reference    Z. Naturforsch. 52a, 249—258 (1997); received August 30 1996 
  Published    1997 
  Keywords    35 C1 NQR study, trichloroacetyl, valine, crystal and molecular structure 
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 TEI-XML for    default:Reihe_A/52/ZNA-1997-52a-0249.pdf 
 Identifier    ZNA-1997-52a-0249 
 Volume    52