Multiple diffraction in spinel and the space‐group ambiguity

The elimination of the ambiguity in the assignment of a space group for the spinel structure depends upon the detection of very weak `forbidden reflexions' in the presence of substantial multiple diffraction. Attention is drawn to the importance of the latter in the case of neutron diffraction when the wavelength is suitable for revealing structural detail. Practical experience shows that single-crystal electron diffraction has distinct advantages for the observation of the forbidden reflexions from spinels, although high-order intensity data are essential for a proper structure-parameter refinement.