SIR97 is the integration of two programs, SIR92 and CAOS, the ®rst devoted to the solution of crystal structures by direct methods, the second to re®nement via least-squares±Fourier procedures. Several new features have been introduced in SIR97 with respect to the previous version, SIR92: greater automatization, increased ef®ciency of the direct methods section, and a powerful graphics interface. The program also provides publication tables and CIF ®les.

EXPO2013, the heir of EXPO2009, has been enriched by a variety of new algorithms and graphical tools aiming at strengthening the individual steps of the powder structure solution pathway. Particular attention has been addressed to the procedures devoted to improving structural models provided by direct methods in ab initio approaches. In addition, a new procedure has been implemented, working in direct space, which may be chosen by the user as an alternative to the traditional simulated annealing algorithm.

EXPO is the integration of two programs, EXTRA and SIRPOW.92, the ®rst devoted to full powder pattern decomposition and the second to the solution and re®nement of crystal structures. The program is able to exploit the prior information obtained during the crystal structure solution process for improving the classical decomposition. EXPO also allows preliminary cycles of Rietveld re®nement.

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.

Extraction of structure-factor amplitudes from a powder diffraction pattern is not a straightforward procedure. Peak overlapping and background estimation are the main obstacles to the process: they may introduce strong correlations among reflection intensities and heavy errors in their estimates. The program EXTRA is described, which, on the basis of the Le Bail algorithm, is able reliably to estimate the structure-factor amplitudes in a fully automatic way.