General Information

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        EXPO2014

       The program  EXPO2014 (Altomare et al., 2013) is the evolution of EXPO2009 (Altomare et al., 2009).  EXPO2014 performs all the steps of the ab-initio structure solution by powder data: indexing, space group determination, estimation of the reflection integrated intensities, structure solution by Direct/Patterson methods or/and by direct space/hybrid approaches, model refinement by Rietveld technique

The program has been designed to:


Program specification

       X-ray, synchrotron or neutron diffraction data can be used. There are no limits on the number of counts in the pattern. The maximum number of reflections is 3000.

The background of system

        EXPO2014,  the updated version of EXPO2009 is able to solve crystal structures from unindexed powder diffraction pattern. Its main steps are (select the topic for more details):

Indexing

       An automatic peak search routine generates a list of "d" values corresponding to the experimental peaks. The values are processed for providing the cell parameters.

Space Group Determination

       A statistical analysis is performed by using the experimental diffraction intensities compatible with the identified crystal system. The procedure is able to provide a list of all the possible extinction symbols ranked according to their probability value. For each of them, the corresponding list of compatible space groups is supplied via graphic interface.

Structure Solution

       Structure solution can be carried out by the two alternative following methods:

Rietveld Refinement

       The structure model is refined by Rietveld method.

Files generated by EXPO2014

       EXPO2014 creates the following files (in the work directory):
- a direct access file to preserve data and results (name.bin);
- an ascii file containing the Miller indices (hkl) and integrated intensities of the generated reflections (name.hkl);
- an ascii file to store peak positions if the indexing process has been carried out (name.pea);

- output file containing information about all the steps of structure determination (name.out).

Authors

A. Altomare(*),C. Cuocci(*), C. Giacovazzo(*),  A. Moliterni(*), R. Rizzi(*).

(*) Institute of Crystallography CNR, (Bari) - Italy

Support

sirmail@ic.cnr.it
http://www.ic.cnr.it/

Acknowledgements

The authors are indebted to Giovanni Luca Cascarano and Mariarosaria Mallamo for their help in the development of the graphic environment.

Main References

       

Altomare, A., Camalli, M.,  Cuocci, C., Giacovazzo, C., Moliterni, A. &  Rizzi, R. (2009). J. Appl. Cryst. 42, 1197-1202.

Altomare, A., Cuocci, C., Giacovazzo, C., Moliterni, A., Rizzi, R., Corriero, N. & Falcicchio, A. (2013). J. Appl. Cryst., Submitted.









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