Concerning intensity profiles.
The kinematical derivation of intensity profiles is considered. It is shown that the shapes of the profiles depend not only on the shape of the crystal but also on the crystal system and axial ratios of the unit cell and on the angles between the direction of the diffracted beam and the cell axes. For all crystal shapes, the widths of the profiles are determined by the Lorentz factor and the mean thickness of the crystal in the direction of the diffracted beam. The similarity of the intensity distributions of cubiform and spherical crystals is discussed. It is shown that almost identical results are obtained for the kinematical intensity profiles of a plane parallel plate having a large crystal edge ratio bathed in the beam and the dynamical profiles of thin plane parallel plates with infinite lateral extension. Extinction-corrected profiles of the plane parallel plate are compared with the results of the dynamical theory. In the case of a spherical crystal, the primary-extinction correction factor, y(p), obtained with extinction-corrected profiles is compared with y(p) commonly used in structure analysis.
Rossmanith
Elisabeth
E
Mineralogisch-Petrographisches Institut der Universität Hamburg, D-20146 Hamburg, Grindelallee 48, Germany. rossmanith@mineralogie.uni-hamburg.de