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Using phases retrieved from two‐dimensional projections to facilitate structure solution from X‐ray powder diffraction data
Author(s) -
Xie Dan,
Baerlocher Christian,
McCusker Lynne B.
Publication year - 2011
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889811030214
Subject(s) - high resolution transmission electron microscopy , powder diffraction , diffraction , resolution (logic) , electron diffraction , x ray crystallography , crystallography , transmission electron microscopy , phase (matter) , electron crystallography , x ray , electron density , materials science , chemistry , electron , physics , optics , computer science , artificial intelligence , organic chemistry , quantum mechanics
A single‐crystal charge‐flipping algorithm has been applied to two‐dimensional projections derived from X‐ray powder diffraction data to retrieve structure‐factor phases. These phases proved to be as reliable as those obtained from high‐resolution transmission electron microscopy (HRTEM) images or from precession electron diffraction data. In particular, the stronger reflections tend to be correctly phased. The two‐dimensional electron‐density `images' obtained in this way show the same features as the corresponding HRTEM images, but with higher resolution. Application of the powder charge‐flipping algorithm to the full three‐dimensional powder diffraction data in conjunction with phases derived from several such (arbitrarily selected) projections was found to have a significant and beneficial effect on the structure solution. The approach was first developed using data collected on the complex zeolite TNU‐9, and was then tested further using data for IM‐5 and SSZ‐74, two similarly complex zeolites. All three of these structures were originally solved by combining X‐ray powder diffraction and electron microscopy data, because X‐ray diffraction data alone were not sufficient. In all three cases, the phase information derived from two‐dimensional subsets of the X‐ray powder diffraction data resulted in a significant improvement in the electron‐density maps generated by the powder charge‐flipping algorithm. The inclusion of this phase information allowed all three structures to be determined from the X‐ray data alone. This two‐dimensional X‐ray powder diffraction approach appears to offer a remarkably simple and powerful method for solving the structures of complex polycrystalline materials.