Simultaneous reflexion: its detection and correction for intensity perturbation

The geometrical condition under which simultaneous reflexions occur with a general setting of a crystal has been formulated in three equations in terms of reciprocal-lattice vectors. A procedure is described to correct the intensity data for structure analysis for the intensity perturbation due to simultaneous reflexion. The following practical experimental conditions were taken into account: the effect due to the circumstance that the primary and secondary reflexions do not always occur exactly at the same time, the divergence and insufficient monochromatization of the incident beam, and a finite size and mosaicity of crystal specimen. The correction for simultaneous reflexion was applied to the X-ray intensity data from diformylhydrazine. It was shown that non-equal intensities among equivalent reflexions could be corrected reasonably by this method.