Gjonnes-Moodie lines

For the space group determination it is necessary to use the information given by the lines of absent intensity (named dynamic absences , Gjonnes Moodie lines or black crosses ) [18] in the reflections which would be completely absent in the weak scattering. In order to distinguish these lines, the following recommendations must be followed ... 

Space group determination is based on the observation of the Gjonnes - Moodie lines [173] in certain forbidden diffraction disks. Reflections that are kinematically forbidden may appear as a result of double diffraction under multibeam dynamic diffraction conditions. If such forbidden spots are produced along pairs of different symmetry-related diffraction paths that are equally excited, the interfering beams may be exactly in antiphase for certain angles of incidence if the structure factors have opposite signs. Since the convergent beam disks are formed by beams with con-... 

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