Space-group determination from powder diffraction data: a probabilistic approach

Experimental powder diffraction diagrams, once indexed and decomposed into single diffraction intensities, can be submitted to statistical analysis for the determination of space-group symmetry. A new algorithm is illustrated, which is able to provide, on a quantitative basis, a probability value for each extinction symbol compatible with the previously established lattice symmetry. The algorithm has been implemented in EXPO2004 [Altomare, Caliandro, Camalli, Cuocci, Giacovazzo, Moliterni & Rizzi ( 2004). J. Appl. Cryst. 37, 1025 - 1028] and has been successfully tested using a large set of experimental data.