A comparison of Weissenberg and diffractometer methods for the measurement of diffuse scattering from disordered molecular crystals

Diffuse X-ray scattering from a disordered molecular crystal [1,4-dibromo-2,5-diethyl-3,6-dimethylbenzene (BEMB1)] has been measured by diffractometer and conventional Weissenberg-film techniques, and a detailed comparison of the two sets of data has been made. An interexperimental agreement factor between the two sets of intensities was about 22%. Statistical tests on the data revealed that a substantial part of this discrepancy was mainly due to systematic differences attributable to alignment problems associated with the need to use large (> 0.5 mm diameter) crystals. It is stressed that X-ray diffuse scattering can be easily and rapidly measured on a diffractometer as part of the normal process of structure determination.