X-Ray Determination of Site Occupation Parameters in Ordered Ternaries Cu(Aux.M1x.)M = Ni,Pd

1990 ◽  
Vol 213 ◽  
Author(s):  
R. Kumar ◽  
C. J. Sparks ◽  
T. Shiraishi ◽  
E.D. Specht ◽  
P. Zschack ◽  
...  
Keyword(s):  
Rietveld Method ◽  
Scattering Data ◽  
X Rays ◽  
X Ray ◽  
Site Occupation ◽  
Intensity Measurements ◽  
X Ray Scattering ◽  
Chemical Phase ◽  
Multiple Wavelengths ◽  
Scattering Factor

ABSTRACTX-ray scattering data obtained for multiple wavelengths with synchrotron radiation were analyzed by the Rietveld method to determine Ni and Pd distributions on the Cu(000) and Au(½½½) sites in the CuAuI tetragonal P4/mmm structure. Alloys of CuAuxM1-x containing 6 at. % Ni or 10 and 25 at. % Pd were processed to obtain maximum ordering. Nickel is predominantly found on the Cu site and most all the Pd is found on the Au site. The uncertainty in site occupation parameters is discussed for various contributions which affect powder intensity measurements. For highly absorbing materials, an observed powder roughness effect decreases the low angle (2θ) intensities relative to the high 2θ intensities. This effect reduces the reliability of the thermal parameters and obscures a proper description of the thermal motion of the two sublattices. Corrections to the X-ray intensity data for surface roughness/porosity effects reduce uncertainties to about ±1 at. % on the refined value of the site occupations. This use of variable wavelength X-rays with simultaneous refinement of the corresponding data is capable of distinguishing site occupations even between two elements of almost equal scattering factor as, for example, Cu and Ni atoms in this investigation. Chemical phase stability is related to the site occupation parameters.

Specular and Off-Specular X-Ray Scattering as Quantitative Structural Probes of Multilayers. Application to MN/IR(111) Superlattices

1995 ◽  
Vol 382 ◽  
Author(s):  
H.M. Fischer ◽  
H.E. Fischer ◽  
M. Bessiere ◽  
J.-F. Bobo ◽  
O. Lenoble ◽  
...  
Keyword(s):  
Deposition Temperature ◽  
Surface Defects ◽  
Single Layer ◽  
Scattering Data ◽  
Length Scale ◽  
X Rays ◽  
Interfacial Roughness ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

ABSTRACTDiffuse scattering of X rays is a particularly useful tool for studying interface and surface defects in single layer films. We have extended this technique to the study of multilayers. The samples are Mn/Ir(111) superlattices where Mn is pseudomorphic to Ir. We have studied three typical samples prepared at different substrate temperatures. Using theoretical analyses and simulations of both specular and off-specular X-ray scattering data at small angles as well as large angles, we show that large length-scale interfacial roughness is mainly due to the formation of terraces during growth at low deposition temperature, whereas small length-scale interfacial roughness occurs preferably at high deposition temperature and is mainly due to an atomic interdiffusion (i.e. the formation of an interface alloy) which manages to maintain a high degree of crystallographic order.

Calculation of scattering curves for macromolecules in solution and comparison with results of methods using effective atomic scattering factors

1983 ◽  
Vol 16 (1) ◽  
pp. 74-82 ◽  
Author(s):  
J. J. Müller
Keyword(s):  
Scattering Data ◽  
Structure Parameters ◽  
Wide Angle ◽  
X Ray ◽  
Rna Molecules ◽  
Dna And Rna ◽  
X Ray Scattering ◽  
Atomic Scattering Factor ◽  
Atomic Scattering ◽  
Scattering Factor

An improved cube method was developed for the computation of X-ray scattering curves of macromolecules in solution. For double-helical DNA and RNA molecules the efficiency of this method is shown. The results are compared with curves calculated by effective atomic scattering factor methods. In the small-angle and in the wide-angle regions the improved cube method is superior to the effective atomic scattering factor methods. This was proved by the calculation of structure parameters and by a comparison with experimental scattering data. On the basis of the improved cube method, models with a reduced structure resolution are deduced for DNA and RNA molecules. The models consisting of the three scattering centres phosphate, sugar and base per nucleotide are equivalent in scattering to the real structure up to a scattering angle of about 0.15 rad for copper radiation.

scholarly journals The reflection of X-rays from anthracene crystals

1933 ◽  
Vol 142 (847) ◽  
pp. 422-447 ◽  
Keyword(s):  
Relative Intensity ◽  
X Rays ◽  
Ray Method ◽  
X Ray ◽  
Intensity Measurements ◽  
X Ray Scattering ◽  
Inorganic Substances ◽  
The Absolute ◽  
Absolute Measurements

The importance of absolute, as opposed to relative, intensity measurements in X-ray crystal analysis has often been stressed, and such measurements may lead, with compounds where one sort of atom is of dominant importance, to a direct and unequivocal determination of the structure. Their value in the analysis of organic compounds, where usually no atoms are predominant in X-ray scattering power, is perhaps not so immediate; nevertheless, the absolute X-ray reflection of a given substance is at least as important a constant as, say, its thermal conductivity, and its determination is a necessary preliminary to any detailed study by the X-ray method. Hitherto such absolute measurements have been confined to inorganic substances e. g. , rock-salt, usually occurring in large crystals. It seemed to be worth while to make a determination of the absolute reflecting power of a typical organic crystal in conditions similar to those employed in the analysis of such crystals, i. e. , using a small crystal completely bathed in a monochromatic pencil of X-rays. A very suitable substance for such a measurement is anthracene , since it is easily obtained pure and in crystals which are reasonably permanent and simple to adjust, but more particularly because its structure is already known in considerable detain and relative intensity measurements described in this paper will enable workers with other crystals to standardize series of relative intensity measurements with the minimum of labour, by comparing directly one of their observed reflections with the (001) reflection from a small weighed crystal of anthracene. The comparison can be made without difficulty, either photographically using an integrating microphotometer or by the ionization method on an ordinary spectrometer.

scholarly journals Structure of the amorphous titania precursor phase of N-doped photocatalysts

RSC Advances ◽  
2021 ◽  
Vol 11 (15) ◽  
pp. 8619-8627
Author(s):  
I. E. Grey ◽  
P. Bordet ◽  
N. C. Wilson
Keyword(s):  
Thermal Analyses ◽  
Real Space ◽  
Ammonia Solution ◽  
Scattering Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Amorphous Titania ◽  
Precursor Phase ◽  
Titania Precursor ◽  
Titanyl Sulphate

Amorphous titania samples prepared by ammonia solution neutralization of titanyl sulphate have been characterized by chemical and thermal analyses, and with reciprocal-space and real-space fitting of wide-angle synchrotron X-ray scattering data.

Mesoscopic structure of SiC fibers by neutron and x-ray scattering

1996 ◽  
Vol 11 (5) ◽  
pp. 1169-1178 ◽  
Author(s):  
Kentaro Suzuya ◽  
Michihiro Furusaka ◽  
Noboru Watanabe ◽  
Makoto Osawa ◽  
Kiyohito Okamura ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Volume Fraction ◽  
X Rays ◽  
X Ray ◽  
Sic Fibers ◽  
X Ray Scattering ◽  
Mesoscopic Structure ◽  
Angle Scattering ◽  
Momentum Transfer Range ◽  
First Time

Mesoscopic structures of SiC fibers produced from polycarbosilane by different methods were studied by diffraction and small-angle scattering of neutrons and x-rays. Microvoids of a size of 4–10 Å in diameter have been observed for the first time by neutron scattering in a medium momentum transfer range (Q = 0.1–1.0 Å−1). The size and the volume fraction of β–SiC particles were determined for fibers prepared at different heat-treatment temperatures. The results show that wide-angle neutron scattering measurements are especially useful for the study of the mesoscopic structure of multicomponent materials.

Resonant Inelastic X-ray Scattering at the ESRF: Hard and Soft X-rays

2012 ◽  
Vol 25 (4) ◽  
pp. 9-15 ◽  
Author(s):  
L. Braicovich ◽  
N. B. Brookes ◽  
G. Ghiringhelli ◽  
M. Minola ◽  
G. Monaco ◽  
...  
Keyword(s):  
X Rays ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals Global Small-Angle X-ray Scattering Data Analysis of Triacylglycerols in the Molten State (Part I)

2018 ◽  
Vol 122 (45) ◽  
pp. 10320-10329 ◽  
Author(s):  
Amin Sadeghpour ◽  
Marjorie Ladd Parada ◽  
Josélio Vieira ◽  
Megan Povey ◽  
Michael Rappolt
Keyword(s):  
Data Analysis ◽  
Small Angle ◽  
Scattering Data ◽  
Molten State ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

A multi-length-scale USAXS/SAXS facility: 10–50 keV small-angle X-ray scattering instrument

2013 ◽  
Vol 46 (5) ◽  
pp. 1508-1512 ◽  
Author(s):  
Byron Freelon ◽  
Kamlesh Suthar ◽  
Jan Ilavsky
Keyword(s):  
Small Angle ◽  
Soft Matter ◽  
High Energy ◽  
X Rays ◽  
X Ray ◽  
X Ray Scattering ◽  
Wide Range ◽  
And Performance ◽  
New Facility ◽  
Ray Scattering

Coupling small-angle X-ray scattering (SAXS) and ultra-small-angle X-ray scattering (USAXS) provides a powerful system of techniques for determining the structural organization of nanostructured materials that exhibit a wide range of characteristic length scales. A new facility that combines high-energy (HE) SAXS and USAXS has been developed at the Advanced Photon Source (APS). The application of X-rays across a range of energies, from 10 to 50 keV, offers opportunities to probe structural behavior at the nano- and microscale. An X-ray setup that can characterize both soft matter or hard matter and high-Zsamples in the solid or solution forms is described. Recent upgrades to the Sector 15ID beamline allow an extension of the X-ray energy range and improved beam intensity. The function and performance of the dedicated USAXS/HE-SAXS ChemMatCARS-APS facility is described.

Reconstruction of viruses from solution x-ray scattering data

1995 ◽  
Author(s):  
Yibin Zheng ◽  
Peter C. Doerschuk ◽  
John E. Johnson
Keyword(s):  
Scattering Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering
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