Structural characterisation of industrially relevant polymorphic materials from powder diffraction data

To fully characterize a polymorphic system, it is necessary to know the structural properties of all polymorphs formed by the molecule of interest. Traditionally, single-crystal X-ray diffraction techniques have been used for this purpose, although different polymorphic forms of a given molecule can differ significantly in crystal quality and in many cases only one or a few of the polymorphs yield single crystals that are suitable for investigation by single-crystal X-ray diffraction. Structural characterization of the other polymorphs must be carried out using powder X-ray diffraction. Fortunately, recent years have seen significant developments in techniques for determining crystal structures of molecular solids directly from powder diffraction data. This article highlights the current scope of these techniques and highlights some examples involving studies of polymorphic materials of industrial relevance.