The Hinckley index for kaolinites

Clay Minerals ◽  
1988 ◽  
Vol 23 (3) ◽  
pp. 249-260 ◽  
Author(s):  
A. Plançon ◽  
R. F. Giese ◽  
R. Snyder
Keyword(s):  
Diffraction Pattern ◽  
Defect Structure ◽  
Structural Defects ◽  
X Ray Diffraction ◽  
X Ray ◽  
Linear Fashion ◽  
Non Linear ◽  
Diffraction Patterns ◽  
Good Agreement

AbstractThe (02,11) X-ray diffraction band from a low-defect kaolinite from Cornwall (Hinckley index HI = 1·22) was examined to determine the defect structure. No combination of interlayer translations and admixing of dickite layers accurately modelled the observed diffraction pattern. Calculated diffraction patterns which gave a good agreement with the shape, position, and intensity of the observed peaks, uniformly had inter-peak intensities which were too weak. By treating the kaolinite as a mixture of low-defect (HI = 1·76) and moderate-defect (HI = 0·29) kaolinites, the agreement between the observed and calculated patterns was improved substantially. The existence of a mixture of two kaolinites was also found for a number of low-defect samples (HI > 0·4) from Georgia and Cornwall, and may be of even wider occurrence. The HI, which is very sensitive to the inner-peak intensities, does not estimate the types or abundances of various structural defects (the classical “crystallinity”), but is related directly, in a non-linear fashion, to the proportions of the two kinds of kaolinite which are present in the sample.

Neutron and X-ray diffuse scattering of calcium-stabilized zirconia

1996 ◽  
Vol 52 (1) ◽  
pp. 59-65 ◽  
Author(s):  
Th. Proffen ◽  
R. B. Neder ◽  
F. Frey
Keyword(s):  
Oxygen Vacancy ◽  
Defect Structure ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
Single Vacancy ◽  
Modified Model ◽  
X Ray ◽  
Diffraction Patterns ◽  
Single Oxygen ◽  
Good Agreement

The defect structure of calcium-stabilized zirconia (CSZ) is described in terms of a correlated distribution of microdomains within the cubic matrix of CSZ. The defect structure consists of two types of defects: microdomains based on a single oxygen vacancy with relaxed neighbouring ions and microdomains based on a pair of oxygen vacancies separated by 3 1/2/2a along <111>. The combined evaluation of neutron and X-ray data shows that the previously published structure of the single vacancy domain has to be modified: All cations next to the oxygen vacancy are most likely zirconium. This modified model leads to good agreement between observed and calculated neutron and X-ray diffraction patterns.

scholarly journals The 3D structure of fibrous material is fully restorable from its X-ray diffraction pattern

IUCrJ ◽  
2021 ◽  
Vol 8 (4) ◽  
Author(s):  
Hiroyuki Iwamoto
Keyword(s):  
Diffraction Pattern ◽  
Fibrous Material ◽  
3D Structure ◽  
Wide Field ◽  
Fibrous Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fiber Diffraction ◽  
Puzzle Solving ◽  
Diffraction Patterns

X-ray fiber diffraction is potentially a powerful technique to study the structure of fibrous materials, such as DNA and synthetic polymers. However, only rotationally averaged diffraction patterns can be recorded and it is difficult to correctly interpret them without the knowledge of esoteric diffraction theories. Here we demonstrate that, in principle, the non-rotationally averaged 3D structure of a fibrous material can be restored from its fiber diffraction pattern. The method is a simple puzzle-solving process and in ideal cases it does not require any prior knowledge about the structure, such as helical symmetry. We believe that the proposed method has a potential to transform the fiber diffraction to a 3D imaging technique, and will be useful for a wide field of life and materials sciences.

Evaluation of Reference X-ray Diffraction Patterns in the ICDD Powder Diffraction File

1990 ◽  
Vol 34 ◽  
pp. 369-376
Author(s):  
G. J. McCarthy ◽  
J. M. Holzer ◽  
W. M. Syvinski ◽  
K. J. Martin ◽  
R. G. Garvey
Keyword(s):  
Powder Diffraction ◽  
X Ray Diffraction ◽  
Powder Diffraction File ◽  
Cd Rom ◽  
X Ray ◽  
Binary Oxides ◽  
Diffraction Patterns ◽  
Input Format ◽  
Good Agreement

AbstractProcedures and tools for evaluation of reference x-ray powder patterns in the JCPDSICDD Powder Diffraction File are illustrated by a review of air-stable binary oxides. The reference patterns are evaluated using an available microcomputer version of the NBS*A1DS83 editorial program and PDF patterns retrieved directly from the CD-ROM in the program's input format. The patterns are compared to calculated and experimental diffractograms. The majority of the oxide patterns have been found to be in good agreement with the calculated and observed diffractograms, but are often missing some weak reflections routinely observed with a modern diffractometer. These weak reflections are added to the PDF pattern. For the remainder of the phases, patterns are redetermined.

Powder X-Ray Data for Synthetic Anhydrous Sodium Zirconium Silicates

1987 ◽  
Vol 2 (3) ◽  
pp. 176-179 ◽  
Author(s):  
G. Wilson ◽  
F. P. Glasser
Keyword(s):  
Solid State ◽  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Solid State Reaction ◽  
The Other ◽  
X Ray Diffraction ◽  
Powder Diffraction File ◽  
X Ray ◽  
Sodium Zirconium ◽  
Diffraction Patterns

AbstractA systematic survey of phase formation in the Na2O-ZrO2-SiO2 system has revealed inconsistencies in the number and identity of ternary phases, and of their X-ray powder data. The phases Na2ZrSiO5, Na4Zr2Si3O12, Na2ZrSi2O7 and Na2ZrSi4O11 were prepared by solid-state reaction and their experimental X-ray diffraction patterns measured. Calculated X-ray diffraction patterns were generated by computer, using published crystallographic data, and critically compared with the experimentally observed values. The unit-cell constants were redefined to a greater accuracy than the presently accepted values published in the Powder Diffraction File. Only Na4Zr2Si3O12 produced an X-ray diffraction pattern which agreed with that previously published; those from the other phases were significantly different in both the intensities and positions of the reflections. Data for synthetic Na2ZrSi4O11 identical to the mineral vlasovite are reported.

Low-Angle X-Ray Diffraction and Electron-Microscope Studies of Isolated Cell Membranes

1966 ◽  
Vol 1 (3) ◽  
pp. 287-296
Author(s):  
J. B. FINEAN ◽  
R. COLEMAN ◽  
W. G. GREEN ◽  
A. R. LIMBRICK
Keyword(s):  
Diffraction Pattern ◽  
Close Packing ◽  
Hexagonal Structure ◽  
Erythrocyte Membranes ◽  
Multiphase System ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns ◽  
Guinea Pig Brain ◽  
Isolated Cell

A sequence of low-angle X-ray diffraction patterns obtained during the controlled drying of a preparation of rat erythrocyte ghosts has been interpreted with the aid of corresponding electron micrographs and of a parallel study of myelin isolated from guinea-pig brain. A diffraction pattern that persists down to a level of 10-20% hydration of the sample is believed to arise from the close packing of native erythrocyte membranes. Each membrane is about 100 Å thick and it is suggested that it consists of a predominantly continuous bimolecular layer of lipid, with non-lipid components associated with both surfaces. Further changes in diffraction pattern which accompany continued drying could be interpreted either as a change from a lamellar to a hexagonal structure or as the formation of a multiphase system. Evidence is put forward to support the latter interpretation.

Upsampling speckle patterns for coherent X-ray diffraction imaging

2013 ◽  
Vol 46 (2) ◽  
pp. 319-323 ◽  
Author(s):  
Y. Chushkin ◽  
F. Zontone
Keyword(s):  
Diffraction Pattern ◽  
Imaging Technique ◽  
Real Space ◽  
Field Of View ◽  
Combination Method ◽  
Pixel Size ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Imaging ◽  
Diffraction Patterns

Coherent X-ray diffraction imaging is a lensless imaging technique where an iterative phase-retrieval algorithm is applied to the speckle pattern, the far-field diffraction pattern produced by an isolated object. To ensure convergence to a unique solution, the diffraction pattern must be oversampled by a factor of two or more. Since the resolution in real space depends on the maximum wave vector where the intensity is detected,i.e.on the detector field of view, there is a practical limitation on oversampling in reciprocal space and resolution in real space that is ultimately determined by the number of pixels. This work shows that it is possible to reduce the effective pixel size and maintain the detector field of view by applying a linear combination method to shifted diffraction patterns. The feasibility of the method is demonstrated by reconstructing the images of test objects from diffraction patterns oversampled in each dimension by factors of 1.3 and 1.8 only. The described approach can be applied to any diffraction or imaging technique where the resolution is compromised by a large pixel size.

An expert system for the structural characterization of kaolinites

Clay Minerals ◽  
1990 ◽  
Vol 25 (3) ◽  
pp. 249-260 ◽  
Author(s):  
A. Plançon ◽  
C. Zacharie
Keyword(s):  
Expert System ◽  
Defect Structure ◽  
Defect Structures ◽  
X Ray Diffraction ◽  
Diffraction Profile ◽  
X Ray ◽  
Diffraction Patterns ◽  
Xrd Patterns

AbstractUntil recently, the determination of the defect structures (previously referred to incorrectly as “crystallinity”) of kaolinites has been obtained in one of two ways: (1) measurement of the Hinckley index, or (2) by comparing calculated X-ray diffraction patterns based on a model of the defect structure (including types of defects and abundances) with experimental diffraction profiles. The Hinckley method is simple and easy to perform but contains no real information about the defect structure. Calculated XRD patterns are based on real defects but these calculations are time consuming and require some skill in application. Another approach is proposed: an expert system which will accurately describe the defect structure of kaolinites based on a few measurements taken from a normal powder diffraction profile. This system has been verified for nine kaolinite samples for which the defect structure was previously determined by comparison of calculated and observed diffraction profiles. The expert system reproduced the correct defect structure for each of the samples.

An Application of Multigrain Approaches to the Structural Solution of Grains from Polycrystalline Samples

2019 ◽  
Vol 288 ◽  
pp. 119-123 ◽  
Author(s):  
Jav Davaasambuu ◽  
Jon Wright ◽  
Henning O. Soerensen ◽  
Soeren Schmidt ◽  
Henning F. Poulsen ◽  
...  
Keyword(s):  
Structural Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Experimental Parameters ◽  
Resolution Level ◽  
Diffraction Patterns ◽  
The Individual ◽  
Individual Grains ◽  
Comparison Of The Results ◽  
Good Agreement

The overlap of diffraction spots from different grains was investigated to understand the influence of experimental factors on the x-ray diffraction data quality and to optimize the experimental parameters for data collection on polycrystalline samples. Diffraction patterns for photoactive polycrystals were indexed and sorted with respect to grains using multigrain approaches. The indexing of diffraction spots and the identification of grains for tetrathiafulvalene-p-chloranil samples were performed using the ImageD11, GrainSpotter, GRAINDEX and Cell_now programs. In many cases, comparison of the results from these programs shows good agreement. For the individual grains from polycrystalline samples, the crystal structure was solved and refined using the SHELXTL program. After the structural refinement of the grains, the best and the average R1 values were 1.93% and 2.06%, respectively, which are on a comparable resolution level with that obtained from the x-ray single crystal measurements.

Powder-Pattern: A System of Programs for Processing and Interpreting Powder Diffraction Data

1982 ◽  
Vol 26 ◽  
pp. 63-72 ◽  
Author(s):  
Nikos P. Pyrros ◽  
Camden R. Hubbard
Keyword(s):  
Unit Cell ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Pure Phase ◽  
Diffraction Patterns ◽  
Better Than ◽  
Good Agreement

The production of standard x-ray diffraction patterns at NBS imposes special requirements in the data processing of powder patterns. The patterns should be complete and have an overall accuracy of better than 0.01 degree two theta. To ensure completeness all the observable peaks should be indexed. To make certain that the sample is a pure phase, weak peaks have to be identified as well.The indexing of all the peaks implies that the cell constants must be known and there should be a good agreement between all the calculated and observed peak positions. In practice this is achieved by a least-squares refinement of the unit cell parameters. This serves as a test of the assumed unit cell and also as an interpretation of the observed peaks. Finally, an attempt is made to identify the space group. This step also requires the identification of weak peaks. The agreement of a known space group with the observed reflections further confirms the purity of the sample.

scholarly journals PHASE ANALYSIS OF NITI WIRE BASED ON SYNCHROTRON 2D X-RAY DIFFRACTION PATTERN IN MATLAB

2017 ◽  
Vol 9 ◽  
pp. 8
Author(s):  
Martin Dudr ◽  
Daniel Šimek ◽  
Jan Drahokoupil
Keyword(s):  
Diffraction Pattern ◽  
Phase Analysis ◽  
Phase Content ◽  
X Ray Diffraction ◽  
Niti Wire ◽  
X Ray ◽  
Combined Load ◽  
Quantitative Phase ◽  
Debye Ring ◽  
Diffraction Patterns

This paper deals with simplified phase analysis of 2D diffraction patterns obtained using microfocused X-ray at various places of superelastic NiTi wire under combined load. For this purpose, MATLAB routines and functions were created, which carry out integration of the patterns in various sectors of Debye ring, fitting of the patterns by a mixture of austenite and martensite (having neglected the R-phase) and successive evaluation of the quantitative phase content. The most crucial simplificating assumptions were: the neglection of the R-phase and the assumption of a) fibre texture or b) no texture.

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