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Advances in space‐group determination from powder diffraction data
Author(s) -
Altomare Angela,
Camalli Mercedes,
Cuocci Corrado,
Giacovazzo Carmelo,
Moliterni Anna Grazia Giuseppina,
Rizzi Rosanna
Publication year - 2007
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889807027501
Subject(s) - extinction (optical mineralogy) , group (periodic table) , reflection (computer programming) , diffraction , space (punctuation) , set (abstract data type) , quality (philosophy) , interval (graph theory) , algorithm , order (exchange) , mathematics , powder diffraction , statistics , computer science , optics , crystallography , combinatorics , physics , chemistry , quantum mechanics , finance , economics , programming language , operating system
The space‐group determination process by powder diffraction data is not straightforward. The low accuracy of the reflection intensities may invalidate the calculation of the probability associated to each extinction group that is compatible with the crystal system determined in the indexation step. Here the combination of the z statistics with two new algorithms is reported: the first checks the quality of each 2θ interval in order to omit doubtful z estimates from the calculations; the second creates a list of reflections with peaks that weakly overlap with any other peak, in order to check if any of them violates the extinction rules of the extinction symbol. The new approach has been applied to a large set of test structures and proved to be much more efficient than the procedure based only on the z statistics.