Charge density measurement in MgH2 by synchrotron X-ray diffraction

2003 ◽  
Vol 356-357 ◽  
pp. 84-86 ◽  
Author(s):  
T. Noritake ◽  
S. Towata ◽  
M. Aoki ◽  
Y. Seno ◽  
Y. Hirose ◽  
...  
Keyword(s):  
Charge Density ◽  
Density Measurement ◽  
X Ray Diffraction ◽  
X Ray

A Combination Method of Charge Density Measurement in Hard Materials Using Accurate, Quantitative Electron and X-ray Diffraction: The α-Al2O3 Case

2003 ◽  
Vol 9 (5) ◽  
pp. 419-427 ◽  
Author(s):  
Victor A. Streltsov ◽  
Philip N.H. Nakashima ◽  
Andrew W.S. Johnson
Keyword(s):  
Charge Density ◽  
Multiple Scattering ◽  
Density Measurement ◽  
Bloch Wave ◽  
Combination Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hard Materials ◽  
Structure Factors ◽  
Free Data

Current X-ray diffraction techniques intended for “ideally imperfect” specimens provide structure factors only on a relative scale and ever-present multiple scattering in strong low-angle Bragg reflections is difficult to correct. Multiple scattering is implicit in the quantitative convergent beam electron diffraction (QCBED) method, which provides absolutely scaled structure factors. Conventional single crystal X-ray diffraction has proved adequate in softer materials where crystal perfection is limited. In hard materials, the highly perfect nature of the crystals is often a difficulty, due to the inadequacy of the conventional corrections for multiple scattering (extinction corrections). The present study on α-Al2O3 exploits the complementarity of synchrotron X-ray measurements for weak and medium intensities and QCBED measurement of the strong low-angle reflections. Two-dimensional near zone axis QCBED data from different crystals at various accelerating voltages, thicknesses, and orientations have been matched using Bloch-wave and multislice methods. The reproducibility of QCBED data is better than 0.5%. The low-angle strong QCBED structure factors were combined with middle and high-angle extinction-free data from synchrotron X-ray diffraction measurements. Static deformation charge density maps for α-Al2O3 have been calculated from a multipole expansion model refined using the combined QCBED and X-ray data.

Molecular tapes in the structure of isoguaninium chloride

2017 ◽  
Vol 74 (1) ◽  
pp. 108-112 ◽  
Author(s):  
Urszula Anna Budniak ◽  
Paulina Maria Dominiak
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Charge Density ◽  
Interaction Energy ◽  
Electrostatic Interaction ◽  
Electrostatic Interactions ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Structure

Isoguanine, an analogue of guanine, is of intrinsic interest as a noncanonical nucleobase. The crystal structure of isoguaninium chloride (systematic name: 6-amino-2-oxo-1H,7H-purin-3-ium chloride), C5H6N5O+·Cl−, has been determined by single-crystal X-ray diffraction. Structure analysis was supported by electrostatic interaction energy (E es) calculations based on charge density reconstructed with the UBDB databank. In the structure, two kinds of molecular tapes are observed, one parallel to (010) and the other parallel to (50\overline{4}). The tapes are formed by dimers of isoguaninium cations interacting with chloride anions. E es analysis indicates that cations in one kind of tape are oriented so as to minimize repulsive electrostatic interactions.

X-ray diffraction study of the transient structure of sliding charge density waves in NbSe3

2002 ◽  
Vol 12 (9) ◽  
pp. 181-182
Author(s):  
H. Requardt ◽  
D. Rideau ◽  
R. Danneau ◽  
A. Ayari ◽  
F. Ya Nad ◽  
...  
Keyword(s):  
Charge Density ◽  
Density Wave ◽  
Charge Density Waves ◽  
X Ray Diffraction ◽  
X Ray ◽  
Slowing Down ◽  
Current Contact ◽  
Decay Profile ◽  
Stretched Exponential Decay ◽  
Transient Structure

We present high resolution X-ray diffraction measurements on NbSe3 of the charge-density-wave (CDW) relaxation from the deformation created by the sliding of the CDW. The data are taken in the temperature range 75 K < T < 105 K in the upper-CDW phase of NbSe, and cover spatial positions up to $8OO~\mu$m from the current contact. Convenient fits to the data are obtained by a stretched exponential decay profile yielding exponents μ in the range of 0.4–0.7 and relaxation time-scales τ of the order of 1–150 ms. becoming faster with increasing sample temperature and slowing down with increasing distance from the current contact.

A single charge density wave dislocation observed by coherent X-ray diffraction

2005 ◽  
Vol 131 ◽  
pp. 143-146
Author(s):  
D. le Bolloc'h ◽  
S. Ravy ◽  
J. Dumas ◽  
J. Marcus ◽  
F. Livet ◽  
...  
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Single Charge ◽  
X Ray Diffraction ◽  
X Ray

Charge density distribution in aminomethylphosphonic acid

2010 ◽  
Vol 66 (5) ◽  
pp. 559-567 ◽  
Author(s):  
Rafał Janicki ◽  
Przemysław Starynowicz
Keyword(s):  
Density Distribution ◽  
Charge Density ◽  
Density Functional ◽  
X Ray Diffraction ◽  
Charge Density Distribution ◽  
Functional Theory ◽  
X Ray ◽  
Topological Features ◽  
Aminomethylphosphonic Acid ◽  
Experimental Charge Density

The experimental charge density distribution in aminomethylphosphonic acid has been determined from X-ray diffraction and its topological features have been analyzed. The results have shown that the P—O bonds are highly polarized, moreover the P—OH bond is weaker than the bonds to unprotonated O atoms. These facts have been confirmed by theoretical density functional theory (DFT) calculations, which have shown that the single, strongly polarized bonds within the phosphonate group are modified by hyperconjugation effects.

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