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  • International Union of Crystallography (IUCr)  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Angle Calculations for a `2+2' Surface X-ray Diffractometer (1995)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 318-326 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Angle calculations are presented for a new type of diffractometer, which has two degrees of freedom for the sample and two degrees of freedom for the detector. The sample and detector motions are mechanically uncoupled. This geometry is used to implement a surface diffractometer and the corrections necessary to extract integrated intensities in two of the most useful modes are presented. The relative merits of this geometry and further extensions to it are discussed. Experimental data, showing the existence of an interfacial microstructure at the Si/SiO2 interface, are also presented to illustrate the advantage of this geometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889894011131
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative determination of phases of X-ray reflections from three-beam diffraction. II. Experiments for perfect crystals (1988)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 44 (1988), S. 1073-1078 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The method proposed by Chang & Tang [Acta Cryst. (1988). A44, 1065-1072] of quantitative determination of X-ray reflection phases from multiple diffraction profiles is applied to nearly perfect crystals of gallium arsenide. The detailed intensity-profile-analysis procedures are given. Multiple diffraction profiles obtained with a conventional X-ray source and synchrotron radiation are subjected to this analysis. It is found that, for this particular diffraction example, errors as small as 15° in phase determination are achieved. Errors due to the theoretical approximation, peak position measurement and scaling factor are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767388008189
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of the enantiomorph from intensity measurements of three-beam Bragg-surface diffraction of X-rays (1989)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 45 (1989), S. 703-708 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: An analytical expression for the intrinsic peak width of three-beam Bragg diffraction involving a surface reflection is derived on the basis of the dynamical theory of X-ray diffraction. Utilization of this expression in peak intensity measurements is proved to lead to direct determination of the enantiomorph of the triplet structure-factor invariant involved in a three-beam Bragg-surface diffraction. Effects of polarization on the kinematical peak intensity and on the intrinsic peak width are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767389006008
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative determination of phases of X-ray reflection from three-beam diffraction. III. Experiments on mosaic crystals (1989)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 45 (1989), S. 870-878 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The method proposed by Chang & Tang [Acta Cryst. (1988), A44, 1065-1072] for quantitative determination of phases of X-ray reflection from three-beam diffraction profiles is applied to an organic crystal of (2R, 3 R)-3-acetoxy-5,7-dihydroxy-6-methylflavanone, with a mosaic spread of 0.08°. The expression for the kinematical diffraction intensities is modified according to the kinematical theory of X-ray diffraction in the multibeam regime. Three-beam Umweganregung and Aufhellung diffraction profiles are analyzed. With the help of the modified intensity expression, the crystal symmetry imposed by the space group and the three-beam diffraction geometry, four acentric phases and fourteen centric phases of structure-factor triplets are determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767389009293
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  • 5
    Electronic Resource
    Electronic Resource
    Quantitative determination of phases of X-ray reflections from three-beam diffraction. I. Theoretical considerations (1988)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 44 (1988), S. 1065-1072 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A method of quantitative determination of X-ray reflection phases using three-beam multiple diffraction is described. This method is derived from the dynamical theory of X-ray diffraction. First-order approximation is employed to take care of the multi- beam diffraction situation. Polarization and excitation of wave fields and the Lorentz factor of crystal rotation are considered. For practical purposes, instrumental broadening and crystal mosaicity are included in calculating the diffraction intensity profiles. It is found that in the theoretical formulation the phase-dependent (dynamical) diffraction distribution can be separated from the phase-independent (kinematical) diffraction background. This makes possible the quantitative determination of reflection phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767388008177
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