Reinvestigation of cadmium diphosphate

The crystal structure of the title compound, Cd2P2O7, has been reinvestigated by means of an image‐plate diffraction system. The study confirms the previously determined structure [Calvo & Au (1969). Can. J. Chem.47, 3409–3417], but provides a less biased model and higher precision. The structure consists of alternating layers of isolated P2O7 groups and edge‐sharing CdO6 octa­hedra forming corrugated chains along [10]. The layers and the parallel chains inter­connect by means of corner‐sharing. This room‐temperature structure is actually the average of a modulated structure, which might partly rectify the unusual bond valences.