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  • 1
    Electronic Resource
    Electronic Resource
    Rietveld analysis of powder patterns obtained by TOF neutron diffraction using cold neutron sources (1987)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 20 (1987), S. 411-418 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A computer program has been developed for the Rietveld analysis of time-of-flight neutron diffraction data taken on a high-resolution powder diffractometer, HRP, at the pulsed spallation neutron source, KENS. A new profile shape function is implemented which is optimized for a solid-methane moderator at 20 K. The program has several convenient features such as single-pass operation, multiphase capability, automatic successive refinements and constrained minimization. The results of Rietveld refinements of Si and α-Al2O3 show that the profile shape function fits neutron diffraction patterns taken on the HRP very well, and that very precise crystal-structure parameters can be obtained with this program.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889887086382
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  • 2
    Electronic Resource
    Electronic Resource
    Single-crystal X-ray diffraction study on the hydrogen ordering in Ta2H (1978)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 11 (1978), S. 681-683 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A crystal of Ta2H with a single ordered domain has been prepared by the reaction of hydrogen gas with a tantalum single-crystal. Precession and Weissenberg photographs show the superlattice reflections which are indexed in terms of an orthorhombic unit cell with lattice parameters A = a[2(1 +cos γ)]1/ 2, B = c and C = a[2(1−cos γ)]1/2, where a(= b) = 3.359, c = 3.398 Å and γ = 90.3° are the parameters of the host monoclinic tantalum lattice. Quantitative intensity measurements indicate that these reflections arise mostly from the systematic displacement of metal atoms caused by the ordered hydrogen arrangement. The amount of displacement has been determined as 0.086 Å, which is a little larger than a previous neutron diffraction result (0.057 Å) on Ta2D.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889878014260
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  • 3
    Electronic Resource
    Electronic Resource
    Precise structure analysis by neutron diffraction for RNbO4 and distortion of NbO4 tetrahedra (1993)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 595-600 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Precise crystal structure analysis by neutron powder diffraction is performed for rare-earth orthoniobates (RNbO4: R = La, Nd, Ho and Yb) and the distortion of NbO4 tetrahedra is estimated with the normal-coordinate method. Displacement of the cubic symmetry mode is large and increases with decreasing ionic radius of VIIIR3+. This displacement produces a regular tetrahedron of NbO4. The mean value of Nb–O distances in the regular tetrahedron of RNbO4 crystals is 1.834 Å. This value is nearly equal to the mean bond length for s = 5/4, \overline R = 1.828 Å, estimated by the bond-valence method. Displacements of the other symmetry modes slightly decrease or are almost constant with decreasing ionic radius.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767392013035
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