Abstract
The crystal structure of the small alpha-phase of quinacridone was determined from non-indexed X-ray powder data by means of crystal structure prediction and subsequent Rietveld refinement. This small alpha-phase is another polymorph than the small alpha-phase reported by Lincke G. Lincke and H.-U. Finzel, 1996, , 441-452.. The crystal structures of the small beta and gamma polymorphs were determined from single crystal data. The knowledge of the crystal structures can be used for crystal engineering, , for targeted syntheses of pigments having desired properties, especially for the syntheses of new red pigments.