Automated Crystal Structure Determination Has its Pitfalls: Correction to the Crystal Structures of Iodine Azide

Previously published crystal structure determinations of two modifications of iodine azide (IN₃ ) are corrected. In the original determinations, the very weak X-ray reflections with odd k Miller indices had been discarded, resulting in too small unit cells and models with misordered, partly occupied atomic positions. Using the original diffraction data, refinements with the correct unit cells yield structures of polymeric (-I-N₃ -)_n chains that are interlocked to layers. A skilled look at the primary X-ray data is always recommended to overcome the lack of crystallographic expertise of computers at automated structure determinations.