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  • CHA zeolitescatalytic activitylocation of Cu2+synchrotron powder X-ray diffractionRietveld/maximum entropy method  (1)
  • biological crystallographyeditorialIUCrJ  (1)
  • charge-density researchmedicinal chemistrydrug designinvariomHansen–Coppens multipole modelquantum theory of atoms in molecules  (1)
  • International Union of Crystallography (IUCr)  (3)
  • Periodicals Archive Online (PAO)
  • 2010-2014  (3)
  • 1980-1984
Collection
Keywords
Publisher
  • International Union of Crystallography (IUCr)  (3)
  • Periodicals Archive Online (PAO)
Years
  • 2010-2014  (3)
  • 1980-1984
Year
  • 1
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    International Union of Crystallography (IUCr)
    In: IUCrJ
    Publication Date: 2014-04-08
    Keywords: biological crystallographyeditorialIUCrJ
    Electronic ISSN: 2052-2525
    Topics: Geosciences , Physics
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  • 2
    Publication Date: 2014-11-12
    Description: Accurate structural models of reaction centres in zeolite catalysts are a prerequisite for mechanistic studies and further improvements to the catalytic performance. The Rietveld/maximum entropy method is applied to synchrotron powder X-ray diffraction data on fully dehydrated CHA-type zeolites with and without loading of catalytically active Cu2+ for the selective catalytic reduction of NOx with NH3. The method identifies the known Cu2+ sites in the six-membered ring and a not previously observed site in the eight-membered ring. The sum of the refined Cu occupancies for these two sites matches the chemical analysis and thus all the Cu is accounted for. It is furthermore shown that approximately 80% of the Cu2+ is located in the new 8-ring site for an industrially relevant CHA zeolite with Si/Al = 15.5 and Cu/Al = 0.45. Density functional theory calculations are used to corroborate the positions and identity of the two Cu sites, leading to the most complete structural description of dehydrated silicoaluminate CHA loaded with catalytically active Cu2+ cations.
    Keywords: CHA zeolitescatalytic activitylocation of Cu2+synchrotron powder X-ray diffractionRietveld/maximum entropy method
    Electronic ISSN: 2052-2525
    Topics: Geosciences , Physics
    Location Call Number Expected Availability
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  • 3
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    International Union of Crystallography (IUCr)
    In: IUCrJ
    Publication Date: 2014-11-12
    Description: This article reviews efforts in accurate experimental charge-density studies with relevance to medicinal chemistry. Initially, classical charge-density studies that measure electron density distribution via least-squares refinement of aspherical-atom population parameters are summarized. Next, interaction density is discussed as an idealized situation resembling drug–receptor interactions. Scattering-factor databases play an increasing role in charge-density research, and they can be applied both to small-molecule and macromolecular structures in refinement and analysis; software development facilitates their use. Therefore combining both of these complementary branches of X-ray crystallography is recommended, and examples are given where such a combination already proved useful. On the side of the experiment, new pixel detectors are allowing rapid measurements, thereby enabling both high-throughput small-molecule studies and macromolecular structure determination to higher resolutions. Currently, the most ambitious studies compute intermolecular interaction energies of drug–receptor complexes, and it is recommended that future studies benefit from recent method developments. Selected new developments in theoretical charge-density studies are discussed with emphasis on its symbiotic relation to crystallography.
    Keywords: charge-density researchmedicinal chemistrydrug designinvariomHansen–Coppens multipole modelquantum theory of atoms in molecules
    Electronic ISSN: 2052-2525
    Topics: Geosciences , Physics
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