Rietveld refinement of a wrong crystal structure

Acta Cryst. (2007). B63, 926-932 [doi:10.1107/S0108768107050823)]

Rietveld refinements are used to confirm crystal structures solved from powder diffraction data. The Rietveld refinement of the X-ray powder pattern of γ-quinacridone with the crystal structure of β-quinacridone gives a good fit, and a reasonable looking crystal structure. However, the lattice parameters, molecular conformation and packing are wrong. This example shows that a successful Rietveld refinement is not always final proof of the correctness of a crystal structure.

C. Buchsbaum and M.U. Schmidt