Automation and efficiency in the powder structure solution by EXPO package (Abstract/Comunicazione in rivista)

Type
Label
  • Automation and efficiency in the powder structure solution by EXPO package (Abstract/Comunicazione in rivista) (literal)
Anno
  • 2011-01-01T00:00:00+01:00 (literal)
Alternative label
  • A. Altomare, C. Cuocci, C. Giacovazzo, A. Moliterni and R. Rizzi (2011)
    Automation and efficiency in the powder structure solution by EXPO package
    (literal)
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  • A. Altomare, C. Cuocci, C. Giacovazzo, A. Moliterni and R. Rizzi (literal)
Pagina inizio
  • C204 (literal)
Pagina fine
  • C205 (literal)
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  • A67 (literal)
Rivista
Note
  • Comunicazione (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • Istituto di Cristallografia (IC-CNR) (literal)
Titolo
  • Automation and efficiency in the powder structure solution by EXPO package (literal)
Abstract
  • The EXPO package [1] is a computing program able to successfully provide the structure solution by starting from minimal information: the experimental powder diffraction pattern and the chemical formula of the compound to investigate. EXPO can be used for solving organic, inorganic, metalorganic structures for a large variety of applications. Automation and efficiency are suitably combined in EXPO for performing all the steps of the solution process: indexation, space group determination, intensity extraction, structure solution, model optimization, Rietveld refinement. Automation. Default strategies, identified as the most effective, are selected for carrying out the solution process automatically and quickly. They may fail when the experimental data resolution is bad and/or the structure complexity is remarkable. In these cases, EXPO can promptly switch to appropriate strategies by profiting by a user friendly graphical interface. Efficiency. Innovative theories and computing procedures aiming at making straightforward all the steps of the solution process are integrated in EXPO and widely tested. EXPO is continuously updated and optimized in terms of both computing efficiency and graphical performances. In EXPO the two stages based ab initio approach (in the first stage the intensities are extracted; in the second, the reflections are phased by Direct Methods) [2] is the automatic choice. The model provided by Direct Methods is usually partial and approximate because of well known unavoidable problems in powder diffraction (overlapping, background, preferred orientation). It can be optimized by default [3], [4] and/or non-default strategies [5], [6] which are able to reduce the errors depending on the limited experimental resolution. A very recent study has regarded a new and more effective figure of merit [7], alternative to the classical one. It is able to pick up the phasing trial corresponding to the best solution among several feasible ones. Non ab initio method, requesting the knowledge of the expected molecular geometry and based on Simulated Annealing technique [8, 9], can optionally be attempted particularly in case of solution of organic compounds. Examples of successful automatic runs by EXPO will be discussed in addition to available special strategies. (literal)
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