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HUG and SQUEEZE: using CRYSTALS to incorporate resonant-scattering in the SQUEEZE structure factor contributions to determine absolute structure

Abstract:

The resonant scattering contributions to single crystal X-ray diffraction data enables the absolute structure of crystalline materials to be determined.

Crystal structures can be determined even if they contain considerably disordered regions because a correction is available via a discrete Fourier transform of the residual electron density to approximate the X-ray scattering from the disordered region. However the corrected model can not normally account for resonant scattering from atoms in the disordered region. Straightforward determination of absolute structure from crystals where the strongly resonantly scattering atoms are not resolved has therefore not been possible.

Using an approximate resonant scattering correction to the X-ray scattering from the disordered regions we have developed and tested a procedure (HUG) to recover the absolute structure using conventional Flack x refinement or other post-refinement determination methods.

Results show that in favourable cases the HUG method works well and the absolute structure can be correctly determined. It offers no useful improvement in cases where the original correction for the disordered region scattering density is problematic, for example when a large fraction of the scattering density in the crystal is disordered, or when voids are not occupied equally by the disordered species. Crucially however, if the approach does not work for a given structure, the statistics for the absolute structure measures are not improved, meaning it is unlikely to lead to misassignment of absolute structure.

Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1107/S2053229617013304

Authors


More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Chemistry
Sub department:
Inorganic Chemistry
Role:
Author
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Chemistry
Sub department:
Inorganic Chemistry
Role:
Author

Contributors

Role:
Editor


More from this funder
Funding agency for:
Cooper, RI
Grant:
EP/K013009/1


Publisher:
International Union of Crystallography
Journal:
Acta Crystallographica Section C: Structural Chemistry More from this journal
Volume:
C73
Issue:
11
Pages:
845-853
Publication date:
2017-11-01
Acceptance date:
2017-09-18
DOI:
ISSN:
2053-2296


Keywords:
Pubs id:
pubs:729232
UUID:
uuid:f8cf5a21-02cd-4f24-9619-729a254e940e
Local pid:
pubs:729232
Source identifiers:
729232
Deposit date:
2017-09-18

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