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  • 1975-1979  (3)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    On the significance of 'non-significant' reflexions (1979)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 35 (1979), S. 497-499 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The information content of so-called 'unobserved', or 'non-significant' reflexions obtained by diffractometer measurements has been experimentally studied, using data and input parameters for three previously deter- mined crystal structures. It can be concluded that even those reflexions having the largest σ(I)/I values contain significant information about both thermal and positional atomic parameters. It has been possible to carry out an acceptable refinement of one structure on the basis of only the set of structure factors discarded by the original investigator. Inclusion of the weakest reflexions in the refinements lowers the standard deviations, and so should be standard practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739479001133
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Crystal perfection in a noncentrosymmetric alloy. Refinement and test of twinning of the γ-Cu9Al4 structure (1978)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 34 (1978), S. 399-404 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of Cu9Al4 has been refined on the basis of 114 independent structure factors, averaged from a set of 2416 intensity measurements with a diffractometer on a spherical crystal of 0.05 mm diameter. Graphite-monochromatized Cu Kα radiation was used. The final R value was 2.4% when corrections for absorption and extinction had been applied. Anisotropic thermal parameters were introduced and shown to be significant. The occurrence of coherently scattering antiphase domains was found to be less than I%. All equivalent reflections and Friedel pairs were recorded with graphite-monochromatized Mo Kα radiation for ten selected index combinations. Observed and calculated anomalous dispersion effects were found to match closely, indicating that incoherent twinning was also practically non-existent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739478000807
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Spherical monocrystals for X-ray work obtained by plasma remelting of alloy powder (1978)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 11 (1978), S. 148-150 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Spherical crystals of alloy phases too hard and brittle for grinding can be obtained by partial remelting and solidification of a powder sample. The alloy powder is blown through an argon-plasma jet melting the surface material of individual fragments, which solidify again as nearly perfect spheres. The yield is a mixture of different materials in which it is possible, however, after heat treatment to find good single crystals of the original composition. Spherical single crystals of Cu9Al4 have been produced by this method and used for a high-precision X-ray investigation described elsewhere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889878012923
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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