Kinematic diffraction on a structure with periodically varying scattering function

A theory is developed to describe the kinematic diffraction response of a crystal when it is subjected to a periodically varying external perturbation. It is shown that if a part of the local electron density varies linearly with an external stimulus, the diffracted signal is not only a function of...

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Veröffentlicht in:Acta crystallographica. Section A, Foundations of crystallography Jg. 67; H. 4; S. 327 - 335
Hauptverfasser: Chernyshov, Dmitry, van Beek, Wouter, Emerich, Hermann, Milanesio, Marco, Urakawa, Atsushi, Viterbo, Davide, Palin, Luca, Caliandro, Rocco
Format: Journal Article
Sprache:Englisch
Veröffentlicht: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01.07.2011
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Schlagworte:
Crystal structure
Crystallography
Crystals
Demodulation
Diffraction
Electron density
Filtering
Kinematics
modulation-enhanced diffraction
phase problem
Scattering
Scattering functions
Stimulation
theory
ISSN:0108-7673, 1600-5724, 1600-5724, 2053-2733
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Zusammenfassung:A theory is developed to describe the kinematic diffraction response of a crystal when it is subjected to a periodically varying external perturbation. It is shown that if a part of the local electron density varies linearly with an external stimulus, the diffracted signal is not only a function of the stimulation frequency Ω, but also of its double 2Ω. These frequency components can provide, under certain conditions, selective access to partial diffraction contributions that are normally summed up in the interference pattern. A phasing process applied to partial diffraction terms would allow recovery of the substructure actively responding to the stimulus. Two ways of frequency filtering are discussed (demodulation and correlation) with respect to extracting information from such an experiment. Also considered is the effect of the variation of different structural parameters on the diffraction intensity that have to be accounted for while planning modulation‐enhanced experiments. Finally, the advantages and limitations of the proposed concept are discussed, together with possible experiments.
Bibliographie:ark:/67375/WNG-P4G041DB-T
ArticleID:AYADM5016
istex:D306E9E57486066BC0B8253F9A9E4C3EDB646280
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ISSN:0108-7673
1600-5724
1600-5724
2053-2733
DOI:10.1107/S0108767311010695