scholarly journals Disorder in pentachloronitrobenzene, C6Cl5NO2: a diffuse scattering study

2007 ◽  
Vol 63 (4) ◽  
pp. 663-673 ◽  
Author(s):  
Lynne H. Thomas ◽  
T. Richard Welberry ◽  
Darren J. Goossens ◽  
Aidan P. Heerdegen ◽  
Matthias J. Gutmann ◽  
...  
Keyword(s):  
Diffuse Scattering ◽  
Short Range ◽  
Scattering Data ◽  
X Ray ◽  
Monte Carlo Computer Simulation ◽  
X Ray Scattering ◽  
Scattering Study ◽  
The Mean ◽  
Diffraction Patterns ◽  
Local Relaxation

Monte Carlo computer simulation has been used to interpret and model observed single-crystal diffuse X-ray scattering data for pentachloronitrobenzene, C6Cl5NO2. Each site in the crystal contains a molecule in one of six different basic orientations with equal probability. However, no short-range order amongst these different orientations has been detected. The strong, detailed and very distinctive diffraction patterns can be accounted for almost entirely on the assumption of random occupancy of each molecular site, but with very large local relaxation displacements that tend to increase the neighbouring distances for contacts involving NO2...NO2 and NO2...Cl with a corresponding reduction for those involving Cl...Cl. The results show that the mean NO2...NO2 distance is increased by ∼ 0.6 Å, compared with that given by the average structure determination.

A High-Energy Monochromatic Laue (MonoLaue) X-ray Diffuse Scattering Study of KMnF3 using an Image Plate

1997 ◽  
Vol 30 (1) ◽  
pp. 16-20 ◽  
Author(s):  
A. Gibaud ◽  
D. Harlow ◽  
J. B. Hastings ◽  
J. P. Hill ◽  
D. Chapman
Keyword(s):  
Diffuse Scattering ◽  
High Energy ◽  
Experimental Conditions ◽  
X Ray ◽  
Image Plate ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Diffraction Patterns ◽  
Ray Scattering

The technique of high-energy monochromatic Laue X-ray scattering using image plates to record the diffraction patterns is presented. A tunable wiggler beamline is used as an X-ray source. It is shown that such experimental conditions present many advantages over conventional tube sources and photographic films. A study of diffuse scattering in the perovskite compound KMnF3 is presented to illustrate this in a qualitative way.

Structure of oak wood from the Swedish warship Vasa revealed by X-ray scattering and microtomography

Holzforschung ◽  
2012 ◽  
Vol 66 (3) ◽  
Author(s):  
Kirsi Svedström ◽  
Ingela Bjurhager ◽  
Aki Kallonen ◽  
Marko Peura ◽  
Ritva Serimaa
Keyword(s):  
Cellular Structure ◽  
Short Range ◽  
Average Length ◽  
Cellulose Microfibrils ◽  
Crystalline Cellulose ◽  
Oak Wood ◽  
X Ray ◽  
X Ray Scattering ◽  
The Mean ◽  
Ray Scattering

Abstract The degradation of oak wood of the historical warship Vasa was studied, focusing on cellular structure by X-ray microtomography (μCT) and on the nanostructure of the cell wall by wide- and small-angle X-ray scattering (WAXS, SAXS). Solid samples [polyethylene glycol (PEG)-, impregnated and PEG-extracted] were submitted to X-ray analysis and the results compared to those of recent oak. The cellular structure of the Vasa oak was surprisingly well preserved at the micrometer level, according to the μCT images. As revealed by WAXS, the fraction of crystalline cellulose was lower in the Vasa samples compared with recent oak, but the average length and width of cellulose crystallites (25±2 nm and 3.0±0.1 nm, respectively), and the mean microfibril angles (4–9°), showed no significant differences. Accordingly, the crystalline parts of cellulose microfibrils are well preserved in the Vasa oak. The SAXS results indicated a declined short-range order between the cellulose microfibrils and a higher porosity of the Vasa oak compared with recent oak, which may be explained by modification of the hemicellulose-lignin matrix.

Temperature and Coverage Dependence of the Surface Roughness for the Growth of Cu on Cu(001): An X-ray Scattering Study

2001 ◽  
Vol 672 ◽  
Author(s):  
Cristian E. Botez ◽  
William C. Elliott ◽  
Paul F. Miceli ◽  
Peter W. Stephens
Keyword(s):  
Surface Roughness ◽  
Mean Square ◽  
X Ray ◽  
Homoepitaxial Growth ◽  
Coverage Dependence ◽  
X Ray Scattering ◽  
Roughness Exponent ◽  
Scattering Study ◽  
The Mean ◽  
Ray Scattering

ABSTRACTSynchrotron X-ray scattering was used to study the temperature and coverage dependence of the root-mean-square (rms) surface roughness, σ, during the homoepitaxial growth on Cu(001). At temperatures between 370 and 160K, the rms roughness was found to increase as a power law, σ =Θβ, with the coverage Θ. The roughness exponent, β, amounts to ∼1/2 for T≤200K, and it monotonically decreases with increasing T, reaching β∼1/3 at T=370K. The mean-square roughness measured at a constant coverage of 15ML, σ2 15 ML, also depends on the temperature of the substrate: between 370 and 200K, σ2 15 ML becomes progressively larger at lower temperatures, but at 110K a reentrant smoother growth is observed.

scholarly journals Interpretation of diffuse scattering in the high-Tcsuperconductor HgBa2CuO4+δ

IUCrJ ◽  
2016 ◽  
Vol 3 (5) ◽  
pp. 309-318 ◽  
Author(s):  
T. R. Welberry ◽  
D. J. Goossens
Keyword(s):  
Diffuse Scattering ◽  
Primary Source ◽  
Original Model ◽  
Previous Conclusion ◽  
New Model ◽  
X Ray ◽  
Linear Defects ◽  
X Ray Scattering ◽  
Diffraction Patterns ◽  
Displacement Patterns

Published diffuse X-ray scattering from the high-Tcsuperconductor HgBa2CuO4+δhas been reexamined with a view to developing a model that more satisfactorily accounts for the observed patterns. The present work agrees with the previous conclusion that the doping oxygen atoms form long and isolated interstitial chains that run in both tetragonal directions. However, a distinctly different model is proposed for the accompanying displacement patterns of the atoms surrounding these linear defects. In this new model it is proposed that it is the correlated shifts of the Ba atoms along the length of the defect chains that are the primary source of the observed scattering, and that the variations of intensity in the generated diffuse streaks of scattering originate from lateral shifts of both Hg and Ba atoms away from defects. The new model yields diffraction patterns that are in much more convincing agreement with the observations than the original model.

An X-Ray Scattering Study of Amorphous Hydrogenated Carbon

1992 ◽  
Vol 270 ◽  
Author(s):  
T.M. Burke ◽  
D.W. Huxley ◽  
R.J. Newport ◽  
G. Bushnell-Wye ◽  
J. Franks
Keyword(s):  
Thin Film ◽  
Diffuse Scattering ◽  
Critical Angle ◽  
Diamond Like Carbon ◽  
X Ray ◽  
Amorphous Systems ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Amorphous Hydrogenated Carbon

ABSTRACTThe structure of “diamond-like” carbon, a-C:H has been studied using the Xray diffraction facilities available at the Synchrotron Radiation Source (Daresbury Lab, UK). The principle advantage of using the SRS is that high fluxes are available at short wavelengths (λ ∼ 0.6Å): it is therefore possible to extract the “diffuse” scattering profile associated with all amorphous systems with considerable precision over a very wide K-range. A novel diffraction technique is also described in which the X-ray beam is incident on an as-deposited thin film at or near the critical angle. In this geometry we demonstrate that it is possible to gather diffraction data on -1μm films in-situ.

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