Structure and Electron Density Analysis of Lithium Manganese Oxides by Single-crystal X-ray Diffraction

2003 ◽  
Vol 72 (6) ◽  
pp. 1483-1490 ◽  
Author(s):  
Yasuhiko Takahashi ◽  
Junji Akimoto ◽  
Yoshito Gotoh ◽  
Kaoru Dokko ◽  
Matsuhiko Nishizawa ◽  
...  
Keyword(s):  
Single Crystal ◽  
Electron Density ◽  
Manganese Oxides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lithium Manganese Oxides ◽  
Lithium Manganese ◽  
Density Analysis ◽  
Electron Density Analysis

scholarly journals Crystallographic features of ammonium fluoroelpasolites: dynamic orientational disorder in crystals of (NH4)3HfF7 and (NH4)3Ti(O2)F5

2017 ◽  
Vol 73 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Anatoly A. Udovenko ◽  
Alexander A. Karabtsov ◽  
Natalia M. Laptash
Keyword(s):  
Single Crystal ◽  
Electron Density ◽  
Diffraction Data ◽  
Central Atom ◽  
X Ray Diffraction ◽  
Dynamic Nature ◽  
Orientational Disorder ◽  
High Quality ◽  
Structural Units ◽  
X Ray

A classical elpasolite-type structure is considered with respect to dynamically disordered ammonium fluoro-(oxofluoro-)metallates. Single-crystal X-ray diffraction data from high quality (NH4)3HfF7 and (NH4)3Ti(O2)F5 samples enabled the refinement of the ligand and cationic positions in the cubic Fm \bar 3 m (Z = 4) structure. Electron-density atomic profiles show that the ligand atoms are distributed in a mixed (split) position instead of 24e. One of the ammonium groups is disordered near 8c so that its central atom (N1) forms a tetrahedron with vertexes in 32f. However, a center of another group (N2) remains in the 4b site, whereas its H atoms (H2) occupy the 96k positions instead of 24e and, together with the H3 atom in the 32f position, they form eight spatial orientations of the ammonium group. It is a common feature of all ammonium fluoroelpasolites with orientational disorder of structural units of a dynamic nature.

scholarly journals Model-independent structure factors from powder X-ray diffraction: a novel approach

2013 ◽  
Vol 21 (1) ◽  
pp. 119-126 ◽  
Author(s):  
Tine Straasø ◽  
Ann-Christin Dippel ◽  
Jacob Becker ◽  
Jens Als-Nielsen
Keyword(s):  
Density Functional ◽  
Diamond Powder ◽  
X Ray Diffraction ◽  
Pxrd Pattern ◽  
Functional Theory ◽  
X Ray ◽  
Novel Approach ◽  
Structure Factors ◽  
Density Analysis ◽  
Electron Density Analysis

Under the experimental condition that all Bragg peaks in a powder X-ray diffraction (PXRD) pattern have the same shape, one can readily obtain the Bragg intensities without fitting any parameters. This condition is fulfilled at the P02.1 beamline at PETRA III using the seventh harmonic from a 23 mm-period undulator (60 keV) at a distance of 65 m. For grain sizes of the order of 1 µm, the Bragg peak shape in the PXRD is entirely determined by the diameter of the capillary containing the powder sample and the pixel size of the image plate detector, and consequently it is independent of the scattering angle. As an example, a diamond powder has been chosen and structure factors derived which are in accordance with those calculated from density functional theory methods of theWIEN2kpackage to within an accuracy that allows a detailed electron density analysis.

A synchrotron X-ray study of the electron density in Y2BaCuO5

1996 ◽  
Vol 52 (4) ◽  
pp. 569-575 ◽  
Author(s):  
R. Hsu ◽  
E. N. Maslen ◽  
N. Ishizawa
Keyword(s):  
Synchrotron Radiation ◽  
Single Crystal ◽  
Electron Density ◽  
Mirror Plane ◽  
X Ray Diffraction ◽  
Structural Geometry ◽  
X Ray ◽  
Deformation Density ◽  
State Involvement ◽  
Limited Degree

The deformation density (Δρ) for Y2BaCuO5, barium diyttrium cuprate, determined by single-crystal X-ray diffraction with synchrotron radiation, is affected to only a limited degree by the bonding interactions involving the O anions. Electron density is strongly depleted along the cation–cation contacts within the mirror plane in the structure and is transferred to regions between mirror planes that do not lie along short cation–cation vectors. The structural geometry for the CuO5 moiety, with the Cu atom in the +2 state, closely resembles that of the Cu2O5 group in YBa2Cu3O7−δ , for which the +3 state involvement for Cu has been suggested. Space group Pnma, orthorhombic, Mr = 458.68, a = 12.1793 (7), b = 5.6591 (5), c = 7.1323 (4) Å, V = 491.6 Å3, Z = 4, Dx = 6.197 Mg m−3, λ = 0.9 Å, μ 0.9 = 28.893 mm−1, F(000) = 812, T = 293 K, R = 0.020, wR = 0.020, S = 3.09 (5) for 2225 unique reflections.

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