Development of computational methods for single crystal structure solution

 

TITLE

Development of computational methods for single crystal structure solution

STAFF

Benedetta Carrozzini
Giovanni Luca Cascarano
Carmelo Giacovazzo*
[*] Personale associato

CNR MODULE

Commessa PM.P06.015: Crystallographic Methodologies
Modulo II: Development and application of crystallographic methodologies for single-crystal structure determination

KEYWORDS

Crystallographic methods, structure solution, X-ray diffraction, electron diffraction

COLLABORATIONS
M.C. Burla and G. Polidori, University of Perugia, Italy
E. Mugnaioli and U.Kolb, University of Mainz, Germany
DESCRIPTION

Innovative theories and methods are developed and the related algorithms are implemented in a user-friendly automatic program (Sir2008), making the ab-initio solution of crystal structures more robust and effective, even at non-atomic resolution. X-ray data as well as electron diffraction data can be used. Sir2008, integrated in the package IlMilione, is distributed freely for non-commercial applications from the web site http://wwwba.ic.cnr.it


The research activities are devoted to:
- Resolution Bias Minimization, to reduce the effects of limited experimental data. The procedure involves changes in the profile of electron density peaks and the extrapolation of unobserved high-resolution reflections, in order to improve the phasing process and the quality of the electron density maps.
- Model completion and refinement by CEDM (Cross-correlation Electron Density Modification) technique. This algorithm combines the information contained in an approximate structural model with the experimental information (diffraction data) in order to reconstruct the final correct model.
- Methods to improve the crystal structure solution using electron diffraction data. A new algorithm called BEA (Best Equivalent Amplitude) has been developed in order to overcome the problems related to strong differences among equivalent reflections due to dynamical effects. The use of BEA improves the completeness of the final model.

 

Development of computational methods for single crystal structure solution  - IMG

Crystal structure of SOUA, C28H38O19, space group P212121, before and after the application of the Resolution Bias Correction procedure implemented in Sir2008 (Caliandro et al., 2009, J. Appl. Cryst., 42, 302-307).

 

Development of computational methods for single crystal structure solution  - IMG

Crystal structure of charoite, (K,Sr,Ba,Mn)15-16(Ca,Na)32[(Si70(O,OH)180)](OH,F)4.0*nH2O, space group P21/m, solved by Sir2008 using electron diffraction data (Rozhdestvenskaya et al., 2010, Min. Mag., 74, 159-177).

 

CONTACTS

 

Carrozzini Benedetta
Email : benedetta.carrozziniATic.cnr.it
Tel : +39/080/5929147

 

Last Updated (Tuesday, 07 December 2010 10:41)