Extra electron reflections in concentrated alloys may originate from planar defects, not short-range order

In many concentrated alloys of current interest, the observation of diffuse superlattice intensities by transmission electron microscopy has been attributed to the presence of chemical short-range order. This interpretation is questioned on the basis of crystallographic considerations and theoretical predictions of ordering. The work of Xiao and Daykin [Ultramicroscopy 53 (1994)], which shows how planar defects can produce the exact set of observed peaks, is highlighted as an alternative explanation that would impact the conclusions of a number of recent studies.