X-ray determination of polarity sense by anomalous scattering at an absorption edge

A technique is described for the determination of crystallographic polarity which is generally applicable to large polar crystals containing an element heavier than K. It is an extension and simplification of Cole & Stemple's method in which the intensities diffracted by (00 l) and (00) planes are compared at wavelengths close to an absorption edge of a constituent element. A definitive polarity determination may now be made without previously measuring or assuming values of Δf′ and Δf′′ at the edge.