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Tolborg K, Iversen BB. Electron Density Studies in Materials Research. Chemistry 2019; 25:15010-15029. [DOI: 10.1002/chem.201903087] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Revised: 08/13/2019] [Indexed: 11/07/2022]
Affiliation(s)
- Kasper Tolborg
- Center for Materials CrystallographyDepartment of Chemistry and iNANOAarhus University Langelandsgade 140 8000 Aarhus C Denmark
| | - Bo B. Iversen
- Center for Materials CrystallographyDepartment of Chemistry and iNANOAarhus University Langelandsgade 140 8000 Aarhus C Denmark
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Tolborg K, Jørgensen MRV, Christensen S, Kasai H, Becker J, Walter P, Dippel AC, Als-Nielsen J, Iversen BB. Accurate charge densities from powder X-ray diffraction - a new version of the Aarhus vacuum imaging-plate diffractometer. ACTA CRYSTALLOGRAPHICA SECTION B, STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS 2017; 73:521-530. [PMID: 28762964 DOI: 10.1107/s2052520617006357] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 04/27/2017] [Indexed: 06/07/2023]
Abstract
In recent years powder X-ray diffraction has proven to be a valuable alternative to single-crystal X-ray diffraction for determining electron-density distributions in high-symmetry inorganic materials, including subtle deformation in the core electron density. This was made possible by performing diffraction measurements in vacuum using high-energy X-rays at a synchrotron-radiation facility. Here we present a new version of our custom-built in-vacuum powder diffractometer with the sample-to-detector distance increased by a factor of four. In practice this is found to give a reduction in instrumental peak broadening by approximately a factor of three and a large improvement in signal-to-background ratio compared to the previous instrument. Structure factors of silicon at room temperature are extracted using a combined multipole-Rietveld procedure and compared with ab initio calculations and the results from the previous diffractometer. Despite some remaining issues regarding peak asymmetry, the new diffractometer yields structure factors of comparable accuracy to the previous diffractometer at low angles and improved accuracy at high angles. The high quality of the structure factors is further assessed by modelling of core electron deformation with results in good agreement with previous investigations.
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Affiliation(s)
- Kasper Tolborg
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Mads R V Jørgensen
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Sebastian Christensen
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Hidetaka Kasai
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Jacob Becker
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Peter Walter
- PETRA III, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Ann Christin Dippel
- PETRA III, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Jens Als-Nielsen
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Bo B Iversen
- Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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Kasai H, Nishibori E. Spatial distribution of electrons near the Fermi level in the metallic LaB 6 through accurate X-ray charge density study. Sci Rep 2017; 7:41375. [PMID: 28120900 PMCID: PMC5264647 DOI: 10.1038/srep41375] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 12/20/2016] [Indexed: 11/09/2022] Open
Abstract
Charge densities of iso-structural metal hexaborides, a transparent metal LaB6 and a semiconductor BaB6, have been determined using the d > 0.22 Å ultra-high resolution synchrotron radiation X-ray diffraction data by a multipole refinement and a maximum entropy method (MEM). The quality of the experimental charge densities was evaluated by comparison with theoretical charge densities. The strong inter-octahedral and relatively weak intra-octahedral boron-boron bonds were observed in the charge densities. A difference of valence charge densities between LaB6 and BaB6 was calculated to reveal a small difference between isostructural metal and semiconductor. The weak electron lobes distributed around the inter B6 octahedral bond were observed in the difference density. We found the electron lobes are the conductive π-electrons in LaB6 from the comparison with the theoretical valence charge density. We successfully observed a spatial distribution of electrons near the Fermi level from the X-ray charge density study of the series of iso-structural solids.
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Affiliation(s)
- Hidetaka Kasai
- Division of Physics, Faculty of Pure and Applied Sciences, Center for Integrated Research in Fundamental Science and Engineering &Tsukuba Research Center for Interdisciplinary Materials Science, University of Tsukuba. 1-1-1, Tennodai, Tsukuba, Ibaraki, 305-8571, Japan
| | - Eiji Nishibori
- Division of Physics, Faculty of Pure and Applied Sciences, Center for Integrated Research in Fundamental Science and Engineering &Tsukuba Research Center for Interdisciplinary Materials Science, University of Tsukuba. 1-1-1, Tennodai, Tsukuba, Ibaraki, 305-8571, Japan
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