Quantitative determination of phases of X-ray reflection from three-beam diffraction. III. Experiments on mosaic crystals

摘要

[[abstract]]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.