The Value of X-ray Powder Diffraction Patterns, and the Structure of the Manganese-Aluminum Alloys with Apparent Icosahedral Symmetry

1986 ◽  
Vol 1 (1) ◽  
pp. 14-15 ◽  
Author(s):  
Linus Pauling
Keyword(s):  
Powder Diffraction ◽  
Bragg Reflection ◽  
Icosahedral Symmetry ◽  
X Rays ◽  
X Ray ◽  
California Institute Of Technology ◽  
Tetragonal Crystal ◽  
Institute Of Technology ◽  
Diffraction Patterns ◽  
Angle Of Reflection

I have made use of X-ray powder diffraction patterns for over sixty years. In the summer of 1922, in anticipation of my becoming a graduate student in chemistry, I read the book “X-Rays and Crystal Structure,” by W. H. and W. L. Bragg. Then in September 1922 I arrived in Pasadena, and immediately began to learn how to determine the structure of a crystal by a study of the X-ray diffraction pattern from Roscoe Gilkey Dickinson, who was the first person to have received a Ph.D. degree from the California Institute of Technology (1920). The procedure in use in Pasadena started with the preparation of a photograph showing lines obtained by Bragg reflection from a developed face of a large crystal with monochromatic radiation, usually molybdenum K alpha and beta. Measurement of the angle of reflection gave a set of possible values for the length of the edges of the unit of structure, usually of a cubic, hexagonal, or tetragonal crystal, since the methods were not powerful enough to permit the evaluation of more than two or three parameters. The next step was the preparation of Laue photographs, and their analysis. This was a powerful method, which often led to the correct structures.

Full-field energy-dispersive powder diffraction imaging using laboratory X-rays

2015 ◽  
Vol 48 (1) ◽  
pp. 269-272 ◽  
Author(s):  
Christopher K. Egan ◽  
Simon D. M. Jacques ◽  
Matthew D. Wilson ◽  
Matthew C. Veale ◽  
Paul Seller ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Texture Mapping ◽  
Friction Stir Weld ◽  
Field Energy ◽  
X Rays ◽  
Full Field ◽  
X Ray ◽  
Friction Stir ◽  
Diffraction Imaging ◽  
Diffraction Patterns

A laboratory instrument with the ability to spatially resolve energy-dispersed X-ray powder diffraction patterns taken in a single snapshot has been developed. The experimental arrangement is based on a pinhole camera coupled with a pixelated spectral X-ray detector. Collimation of the diffracted beam is defined by the area of the footprint of a detector pixel and the diameter of the pinhole aperture. Each pixel in the image, therefore, contains an energy-dispersed powder diffraction pattern. This new X-ray imaging technique enables spatial mapping of crystallinity, crystalline texture or crystalline phases from within a sample. Validation of the method has been carried out with a back-to-back comparison with crystalline texture mapping local to a friction stir weld in an aluminium alloy taken using synchrotron radiation.

X-ray powder diffraction and electron diffraction studies of the thortveitite-related L phase, (Zn,Mn)2V2O7

2009 ◽  
Vol 65 (2) ◽  
pp. 160-166 ◽  
Author(s):  
Kevin M. Knowles ◽  
Mary E. Vickers ◽  
Anjan Sil ◽  
Yung-Hoe Han ◽  
Périne Jaffrenou
Keyword(s):  
Electron Diffraction ◽  
Powder Diffraction ◽  
System Analysis ◽  
Bravais Lattice ◽  
Second Phase ◽  
X Rays ◽  
X Ray ◽  
The Difference ◽  
Diffraction Patterns ◽  
A Minor

The phase designated γ-Zn3(VO4)2 reported as a minor second phase in zinc oxide-based varistor materials doped with vanadium oxide and manganese oxide is shown to be the L phase, (Zn1 − x Mn x )2V2O7 (0.188 < x < 0.538), in the pseudo-binary Mn2V2O7–Zn2V2O7 system. Analysis of X-ray powder diffraction patterns and electron diffraction patterns of this phase shows that the previously published a, c and β values for this thortveitite-related phase are incorrect. Instead, Rietveld refinement of the X-ray powder pattern of the L phase shows that it has a monoclinic C lattice with Z = 6, with a  =  10.3791 (1), b = 8.5557 (1), c = 9.3539 (1) Å and β = 98.467 (1)°. Although prior convergent-beam electron diffraction work of `γ-Zn3(VO4)2' confirmed the C Bravais lattice, the space group was found to be Cm rather than C2/m, the difference perhaps arising from the inability of the X-rays to detect small displacements of oxygen. Attempts to refine the structure in Cm did not produce improved R factors. The relationship between the crystal structure of the L phase and the high-temperature C2/m β′-Zn2V2O7 thortveitite-type solid solution is discussed.

Sub-nanosecond X-ray powder diffraction

1990 ◽  
Vol 23 (5) ◽  
pp. 441-443 ◽  
Author(s):  
N. C. Woolsey ◽  
J. S. Wark ◽  
D. Riley
Keyword(s):  
Powder Diffraction ◽  
Laser Light ◽  
Polycrystalline Materials ◽  
Spectral Brightness ◽  
X Rays ◽  
Single Exposure ◽  
Time Resolved ◽  
X Ray ◽  
Titanium Target ◽  
Diffraction Patterns

The X-rays emitted from a laser-produced plasma have been used to obtain powder diffraction patterns with exposures of less than a nanosecond. The X-rays were produced by focusing approximately 50 J of 0.53 μm laser light in a 600 ps (FWHM) pulse to a tight (~100 μm diameter) spot on a solid titanium target. The spectral brightness of the resonance line of the helium-like titanium thus produced was sufficient to record diffraction from LiF powder in a single exposure using the Seemann–Bohlin geometry. These results indicate that time-resolved measurements of the lattice parameters of polycrystalline materials can be made with sub-nanosecond temporal resolution.

scholarly journals Modeling X-ray diffractomerers using ray tracing and parallel coprocessors

2014 ◽  
Vol 70 (a1) ◽  
pp. C1078-C1078
Author(s):  
Xim Bokhimi ◽  
Carlos Gonzalez
Keyword(s):  
Diffraction Pattern ◽  
Ray Tracing ◽  
Powder Diffraction ◽  
X Rays ◽  
Optical Components ◽  
X Ray ◽  
Crystalline Structures ◽  
Fundamental Parameters ◽  
Diffraction Patterns ◽  
Computer Facility

In X-ray powder diffraction, the use of the Rietveld technique to refine crystalline structures requires modeling the diffractometer. Some of the codes using this technique incorporate simple models for it. These codes do not affect the refined parameters only when the X-ray source is a synchrotron with enough X-ray optic to reduce the associated aberrations. When the diffractometer belongs to a standard laboratory, however, the optic associated to it gives rise to large aberrations; for example, asymmetric and shifted peaks that depend on the diffraction angle. When the above codes are used to refine crystalline structures, the refined parameters are non-confident, because they are partially modeling these aberrations. If in the code, the effect of the optical components on the diffraction pattern is modeled correctly, the obtained refined parameters will be more confident. This kind of modeling has been done in the codes that use the fundamental parameters model for the diffractometer. There are two ways to perform this modeling: in one of them the codes use an analytical model for each one of the optical components of the diffractometer; other codes use the ray tracing technique to model the path of the x-rays along the optic. This last technique requires a powerful computer facility. In this work, we present the developing of an open-source code to model the diffractometer by using the ray tracing technique. To reduce the calculation time, the code was written in OpenCL for a computer with a Fermi K20 coprocessor, and for a computer with a Xeon-Phi coprocessor, using the Qt platform for both systems. The device-function generated with this code can be used as input for any other code that models diffraction patterns, or refines crystalline structures. The code can also be used for teaching the effect of the different optical components on an X-ray powder diffraction pattern, including the effect of a wrong alignment of these components.

scholarly journals Simultaneous Multi-Bragg Peak Coherent X-ray Diffraction Imaging

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 312
Author(s):  
Florian Lauraux ◽  
Stéphane Labat ◽  
Sarah Yehya ◽  
Marie-Ingrid Richard ◽  
Steven J. Leake ◽  
...  
Keyword(s):  
Bragg Reflection ◽  
Volume Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystal Substrate ◽  
In Series ◽  
Diffraction Imaging ◽  
Diffraction Patterns ◽  
Lattice Planes ◽  
Oriented Parallel

The simultaneous measurement of two Bragg reflections by Bragg coherent X-ray diffraction is demonstrated on a twinned Au crystal, which was prepared by the solid-state dewetting of a 30 nm thin gold film on a sapphire substrate. The crystal was oriented on a goniometer so that two lattice planes fulfill the Bragg condition at the same time. The Au 111 and Au 200 Bragg peaks were measured simultaneously by scanning the energy of the incident X-ray beam and recording the diffraction patterns with two two-dimensional detectors. While the former Bragg reflection is not sensitive to the twin boundary, which is oriented parallel to the crystal–substrate interface, the latter reflection is only sensitive to one part of the crystal. The volume ratio between the two parts of the twinned crystal is about 1:9, which is also confirmed by Laue microdiffraction of the same crystal. The parallel measurement of multiple Bragg reflections is essential for future in situ and operando studies, which are so far limited to either a single Bragg reflection or several in series, to facilitate the precise monitoring of both the strain field and defects during the application of external stimuli.

Morphological and synchrotron X-ray microdiffraction studies of large columnar CVD diamond crystallites

1999 ◽  
Vol 32 (5) ◽  
pp. 924-933 ◽  
Author(s):  
A. R. Lang ◽  
A. P. W. Makepeace ◽  
J. E. Butler
Keyword(s):  
Vapour Deposition ◽  
Chemical Vapour ◽  
Coarse Grained ◽  
X Rays ◽  
Small Cross Section ◽  
X Ray ◽  
Chemical Vapour Deposition Diamond ◽  
Core Column ◽  
Diffraction Patterns ◽  
Goniometric Measurements

Optical microscopic and goniometric measurements were combined with microradiography, diffraction-pattern analysis and topography to study a 2 mm thick [001]-texture CVD (chemical vapour deposition) diamond film that had developed a coarse-grained structure composed of separate columnar crystallites. Individual columns were capped by large (001) facets, with widths up to 0.5 mm, and which were smooth but not flat, whereas the column sides were morphologically irregular. The refractive deviation of X-rays transmitted through the crystallites was exploited for delineating facet edges, thereby facilitating the controlled positioning of small-cross-section X-ray beams used for recording diffraction patterns from selected volumes in two representative crystallites. Their structure consisted of a [001]-axial core column surrounded by columns in twin orientation with respect to the core. The diamond volume directly below the (001) facets was free from low-angle boundaries, and no dislocation outcrops on the facets were detected. Significant elastic deformation of this volume was only present close to the facet periphery, where misorientations reached a few milliradians. Lattice imperfection was high in the twins, with ∼1° misorientations.

Two examples of quantitative analysis by simulated X-ray powder diffraction patterns

Clay Minerals ◽  
1982 ◽  
Vol 17 (4) ◽  
pp. 393-399
Author(s):  
C. E. Corbato ◽  
R. T. Tettenhorst
Keyword(s):  
Quantitative Analysis ◽  
Pattern Matching ◽  
Powder Diffraction ◽  
X Ray ◽  
Quantitative Estimates ◽  
Powder Diffractometer ◽  
Alternative Method ◽  
Two Samples ◽  
Natural Mixture ◽  
Diffraction Patterns

AbstractQuantitative estimates were made by visually matching computer-simulated with experimental X-ray powder diffractometer patterns for two samples. One was a natural mixture of dickite and nacrite in about equal proportions. The second sample contained mostly quartz with corundum and mullite in small (0.5–1%) amounts. Percentages deduced from pattern matching agreed to within ±10% of the weight fractions of the components determined by an alternative method of analysis.

Applications of High-Resolution Powder X-Ray Diffraction

2007 ◽  
Vol 130 ◽  
pp. 7-14 ◽  
Author(s):  
Andrew N. Fitch
Keyword(s):  
High Resolution ◽  
Synchrotron Radiation ◽  
Powder Diffraction ◽  
X Rays ◽  
X Ray Diffraction ◽  
Crystalline Materials ◽  
X Ray ◽  
Structural Characterisation ◽  
Pdf Analysis

The highly-collimated, intense X-rays produced by a synchrotron radiation source can be harnessed to build high-resolution powder diffraction instruments with a wide variety of applications. The general advantages of using synchrotron radiation for powder diffraction are discussed and illustrated with reference to the structural characterisation of crystalline materials, atomic PDF analysis, in-situ and high-throughput studies where the structure is evolving between successive scans, and the measurement of residual strain in engineering components.

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