• crystal structure solution;
  • EXPO2009;
  • powder diffraction data

The program EXPO2009 is the evolution of EXPO2004 [Altomare, Caliandro, Camalli, Cuocci, Giacovazzo, Moliterni & Rizzi (2004). J. Appl. Cryst. 37, 1025–1028]. EXPO2009 performs all the steps of ab initio structure solution by powder data: indexing, space-group determination, estimation of the reflection integrated intensities, structure solution by direct/Patterson methods and/or by a direct-space/hybrid approach, and model refinement by the Rietveld technique. New procedures have been introduced in EXPO2009 for enhancing the structure solution process, particularly in the case of low-resolution data and/or organic compounds, when traditional approaches like direct methods may fail. The EXPO2009 graphical interface has been optimized and made very user friendly.