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07:26
Synthesis and Microdiffraction at Extreme Pressures and Temperatures
Published on: October 8, 2013
Multipole electron densities and structural parameters from synchrotron powder X-ray diffraction data obtained with a
Bjarke Svane1, Kasper Tolborg1, Kenichi Kato2
1Department of Chemistry, Aarhus University, Aarhus, DK-8000, Denmark.
Summary
Powder X-ray diffraction (PXRD) offers advantages for electron density determination, especially for inorganic solids. While challenging for organic materials, advancements with microstrip detectors show promise for accurate structural parameter refinement from PXRD data.
Area of Science:
- Crystallography
- Materials Science
- Solid-State Chemistry
Background:
- Powder X-ray diffraction (PXRD) presents advantages over single-crystal methods for electron density and structural parameter determination, including lower sample crystallinity requirements and simpler corrections.
- Previous studies demonstrated PXRD's potential for electron density studies in organic materials, but limitations in equipment and data quality hindered widespread adoption.
- Fast microstrip detectors offer potential for improved PXRD studies, yet challenges like channel sensitivity differences have prevented their application in electron density research.
Purpose of the Study:
- To evaluate synchrotron PXRD data obtained with a novel total scattering measurement system (OHGI) for multipole electron density and structural parameter refinement.
- To assess the feasibility of electron density modeling using PXRD data, even with non-ideal samples and setups.
- To determine the suitability of PXRD for accurate electron density and structural analysis in both inorganic and organic materials.
Main Methods:
- Utilized synchrotron powder X-ray diffraction data collected with the OHGI system, comprising 15 MYTHEN microstrip modules.
- Applied multipole expansion models to refine electron densities and structural parameters (atomic positions, displacement parameters).
- Evaluated the quality and reliability of refined electron densities and structural parameters against known material properties.
Main Results:
- Electron density modeling is achievable on high-quality PXRD data, even without dedicated setups or perfect samples.
- The OHGI system with microstrip detectors demonstrated potential for accurate structural parameter refinement, including atomic positions and anisotropic displacement parameters.
- While PXRD is a superior alternative for small-unit-cell inorganic solids, obtaining reliable electron densities for general molecular crystals remains challenging due to data quality and required prior information.
Conclusions:
- Synchrotron PXRD data, particularly from advanced systems like OHGI, can yield accurate structural parameters for organic crystals if aspherical atomic scattering factors are available.
- PXRD is an excellent method for electron density studies of small-unit-cell inorganic solids, potentially surpassing single-crystal diffraction.
- Further development is needed to overcome limitations in data quality and prior information requirements for routine electron density studies of molecular crystals using PXRD.
Keywords:
electron densitymolecular crystalspowder diffractionstructural parameterssynchrotron radiationMore Related Videos
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