Space group determination: improvements in EXPO2004

In the ideal process for crystal structure solution, the determination of the space group usually follows the indexation step. When powder data are used, peak overlap, background definition and possible impurity peaks may hinder the identification of the correct extinction group. The recent automatic procedure implemented in EXPO2004 has been further developed; the modifications are based on additional statistical criteria, with new algorithms for a better definition of the background and for the removal of impurity peaks. The new version also offers a more powerful graphical interface. Failures occur rarely, as shown by examples.