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  • Articles: DFG German National Licenses  (2)
  • 1985-1989  (2)
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  • Articles: DFG German National Licenses  (2)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Evaluation of single-crystal X-ray diffraction data from a position-sensitive detector (1988)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 21 (1988), S. 916-924 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A Fortran program has been developed for the reduction of single-crystal diffraction data from a sequence of adjacent rotation pictures recorded at a fixed X-ray wavelength by an electronic area detector. The electronic pictures (data frames) covering the first 5° of crystal rotation are used to locate strong diffraction spots and to estimate the background. The orientation of the crystal is derived automatically from the list of observed spots and all parameters describing the diffraction pattern are refined. The only input required from the user is the specification of the space group, approximate cell dimensions and detector setting. When the initialization step is finished the program goes back to the first picture and evaluates all data frames in the order they arrive from the measurement. Each element of an electronic picture (pixel) is labelled by the indices of the nearest reflection using the current refined parameters describing the diffraction geometry. If the pixels close to its nearest reflection the counts contribute to the three-dimensional profile; otherwise the counts are used to update the background. Each profile is represented as if the reflection had followed the shortest path through the Ewald sphere and had been recorded on the surface of the sphere. Reflections close to the Ewald sphere are kept in a hash table to allow rapid access for updating the profiles. Reflections which have completely passed through the Ewald sphere are removed from the table and saved for further processing. Intensities are estimated by fitting their profiles to an average shape learned from strong neighbouring reflections. Smoothly varying scaling factors are applied to the Lp-corrected intensities which minimize discrepancies between symmetry-related reflections and fit to a reference data set if available.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889888007903
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Automatic indexing of rotation diffraction patterns (1988)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 21 (1988), S. 67-72 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A method is described which assigns indices to a set of single-crystal reflections recorded by the rotation-oscillation technique using a fixed X-ray wavelength. It is assumed that the space group and approximate unit-cell parameters are known. The unknown crystal orientation is determined directly from the observed diffraction pattern of one or several oscillation data records. A local indexing procedure is described which tolerates large initial errors in the parameters controlling the diffraction pattern. These parameters are refined subsequently, thereby satisfying the constraints imposed by the space-group symmetry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889887009737
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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