Ind_X: program for indexing single-crystal diffraction patterns

2017 ◽  
Vol 50 (2) ◽  
pp. 647-650 ◽  
Author(s):  
A. Morawiec
Keyword(s):  
Single Crystal ◽  
Diffraction Data ◽  
Reciprocal Lattice ◽  
Primitive Cell ◽  
Single Crystal Diffraction ◽  
Test Volume ◽  
Lattice Matching ◽  
Essential Step ◽  
Testing Potential ◽  
Diffraction Patterns

Indexing is an essential step in analysis of diffraction patterns. Diffraction of monochromatic radiation by a single crystal provides approximate positions of some nodes of the reciprocal lattice of the crystal, and the indexing problem lies in determining a lattice matching these positions. Ind_X is a program for indexing diffraction data given in the form of several approximate reciprocal lattice nodes. The applied method relies on testing potential volumes of the primitive cell of the reciprocal lattice. A subset of reciprocal lattice vectors supporting a given test volume is used to obtain tentative lattice bases. These are bases of low-index superlattices of lattices based on triplets of supporting vectors. The Ind_X solution of the indexing problem consists of a list of best bases. The method turns out to be quite robust to data inaccuracies and spurious reflections. The program is relatively versatile, easily operated and freely accessible.

Indexing of multi-particle diffraction data in a high-pressure single-crystal diffraction experiment

2013 ◽  
Vol 46 (2) ◽  
pp. 387-390 ◽  
Author(s):  
Hui Li ◽  
Xiaodong Li ◽  
Meng He ◽  
Yanchun Li ◽  
Jing Liu ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
High Pressure ◽  
Single Crystal ◽  
Single Crystals ◽  
Diffraction Data ◽  
Reciprocal Lattice ◽  
Powder Pattern ◽  
Diffraction Experiment ◽  
Crystal Data ◽  
Single Crystal Diffraction

High-pressure single-crystal diffraction experiments often suffer from the crushing of single crystals due to the application of high pressure. Consequently, only diffraction data resulting from several particles in random orientations is available, which cannot be routinely indexed by commonly used methods designed for single-crystal data. A protocol is proposed to index such diffraction data. The techniques of powder pattern indexing are first used to propose the possible lattice parameters, and then a genetic algorithm is applied to determine the orientation of the reciprocal lattice for each of the particles. This protocol has been verified experimentally.

A remark on ab initio indexing of electron backscatter diffraction patterns

2021 ◽  
Vol 54 (6) ◽  
Author(s):  
Adam Morawiec
Keyword(s):  
Single Crystal ◽  
Ab Initio ◽  
Diffraction Data ◽  
Electron Backscatter Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Electron Backscatter ◽  
Diffraction Patterns ◽  
Backscatter Diffraction

There is a growing interest in ab initio indexing of electron backscatter diffraction (EBSD) patterns. The methods of solving the problem are presented as innovative. The purpose of this note is to point out that ab initio EBSD indexing belongs to the field of indexing single-crystal diffraction data, and it is solved on the same principles as indexing of patterns of other types. It is shown that reasonably accurate EBSD-based data can be indexed by programs designed for X-ray data.

scholarly journals Single-crystal diffraction data from powder samples via SFX

2014 ◽  
Vol 70 (a1) ◽  
pp. C1449-C1449
Author(s):  
Tao Zhang ◽  
Shifeng Jin ◽  
Yuanxin Gu ◽  
Yao He ◽  
Haifu Fan
Keyword(s):  
Single Crystal ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Monte Carlo Integration ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
Single Experiment ◽  
X Ray ◽  
Powder Samples ◽  
Diffraction Patterns

With the serial femtosecond crystallography (SFX) [1] using hard X-ray free-electron laser as light source, it is possible to obtained three-dimensional single-crystal diffraction data from powder samples consisting of submicron crystal grains. This offers two advantages. First, complicated crystal structures far beyond the ability of powder X-ray diffraction analysis now can be solved easily; second, mixtures of two or more crystalline components can be examined in a single experiment. The percentage of each component can be determined accurately and the crystal structure of them can be solved readily. Simulating calculations were performed with a mixture of two different kinds of zeolites. The program suite CrystFEL [2] was used for simulating SFX diffraction patterns, diffraction indexing and Monte-Carlo integration of diffraction intensities. The program suite SHELX [3] was used for structure determination. Satisfactory results have been obtained and will be discussed in detail.

Reverse Monte Carlo refinements of nanoscale atomic correlations using powder and single-crystal diffraction data

2012 ◽  
Vol 45 (1) ◽  
pp. 106-112 ◽  
Author(s):  
Victor Krayzman ◽  
Igor Levin
Keyword(s):  
Monte Carlo ◽  
Electron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Reverse Monte Carlo ◽  
Single Crystal Diffraction ◽  
Total Scattering ◽  
X Ray ◽  
Simultaneous Fitting ◽  
Diffraction Patterns

Combined refinements of local atomic structure that involve simultaneous fitting of powder-averaged and single-crystal data were implemented as an extension to the publicly availableRMCProfilesoftware. The refinements employ the reverse Monte Carlo method to fit neutron total scattering data, the neutron Bragg profile, extended X-ray absorption fine structure (EXAFS) and structured diffuse scattering in electron diffraction. The procedure was tested using simulated data generated for a realistic model of perovskite-like KNbO3, which exhibits strongly correlated Nb and O displacements. The results indicated that fitting the powder data (i.e.total scattering or total scattering plus EXAFS) alone fails to reproduce the nanoscale range of displacement correlations. Simultaneous fitting of the powder data and the patterns of diffuse intensity in single-crystal electron diffraction patterns returns significantly more accurate correlation characteristics. The approach and the computer software described in this contribution are not limited to electron diffraction patterns as other types of single-crystal diffraction data (i.e.X-ray or neutron) can be included in the fit.

Leverage analysis of X-ray single crystal diffraction data from orthopyroxene and pigeonite

2002 ◽  
Vol 14 (4) ◽  
pp. 773-783 ◽  
Author(s):  
Marcello Merli ◽  
Fernando Cámara ◽  
Chiara Domeneghetti ◽  
Vittorio Tazzoli
Keyword(s):  
Single Crystal ◽  
Diffraction Data ◽  
Single Crystal Diffraction ◽  
X Ray

The structures of the plagioclase felspars: VII. The heat treatment of intermediate plagioclases

1956 ◽  
Vol 31 (235) ◽  
pp. 306-313 ◽  
Author(s):  
P. Gay ◽  
M. G. Bown
Keyword(s):  
Heat Treatment ◽  
Low Temperature ◽  
Single Crystal ◽  
High Temperatures ◽  
Composition Range ◽  
Heat Treatments ◽  
Careful Study ◽  
Single Crystal Diffraction ◽  
Diffraction Patterns

SummaryPrevious work has established that natural ‘low-temperature’ intermediate plagioclases show single-crystal diffraction patterns in which the subsidiary reflections are split into two; the separation of these split reflections appears to be dependent on the composition of the felspar. Several of these specimens have been subjected to varying heat treatments and their diffraction patterns examined.It is found that over the whole composition range the split subsidiary reflections have disappeared after treatment at high temperatures, and only the principal felspar reflections, which are characteristic of an albite-like structure, remain. Natural specimens initially showing anomalous patterns can also be homogenized in this way by suitable heat treatments. A careful study of the mode of disappearance shows that the separation of the subsidiary reflections is unchanged as long as they remain visible.The structural and petrological implications of this work are discussed.

Anharmonicity of potentials of atoms in potassium hydrogensulfide (KDS) determined by neutron single-crystal diffraction

2000 ◽  
Vol 56 (6) ◽  
pp. 988-992 ◽  
Author(s):  
Frank Haarmann ◽  
Herbert Jacobs ◽  
Manfred Reehuis ◽  
Anja Loose
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Order Approximation ◽  
Single Crystal Diffraction ◽  
Acta Cryst ◽  
Small Deviations ◽  
Molecular Group ◽  
Diffraction Patterns ◽  
Temperature Factors ◽  
Atom Potential

Potassium hydrogensulfide (KHS) is an ionic compound with an anionic molecular group HS^-. The fast reorientational disorder of the anions was determined for the ambient temperature modification [R\bar 3m; Jeffrey (1974). Can. J. Phys. 52, 2370–2378]. Single crystals are available now as protonated or deuterated specimens. With neutron single-crystal diffraction at room temperature, a considerable anharmonicity of the atom potential of the H or D atoms was observed. Even the thermal motions of K and S atoms show small deviations from an isotropic probability density function, which can be modelled using anharmonic temperature factors. The temperature factors of the atoms were expanded into a Gram–Charlier series [Kuhs (1992). Acta Cryst. A48, 80–98] in order to evaluate the anharmonicity quantitatively. Parameters up to a fourth-order approximation are relevant for the D atoms. Results from neutron single-crystal diffraction are compared with split-atom models extracted from neutron powder diffraction patterns of fully deuterated samples.

The single crystal diffraction patterns of silicon

1962 ◽  
Vol 12 (10) ◽  
pp. 764-775 ◽  
Author(s):  
R. Bubáková ◽  
J. Drahokoupil ◽  
A. Fingerland
Keyword(s):  
Single Crystal ◽  
Single Crystal Diffraction ◽  
Diffraction Patterns

A synchrotron X-ray diffraction analysis of near-stoichiometric LiNbO3

2001 ◽  
Vol 216 (8) ◽  
Author(s):  
B. Etschmann ◽  
N. Ishizawa ◽  
V. Streltsov ◽  
S. Oishi
Keyword(s):  
Single Crystal ◽  
Diffraction Analysis ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray

AbstractSingle-crystal diffraction data was collected at 120 and 294 K for an approximately spherical LiNbO

Simulations of X-ray diffraction of shock-compressed single-crystal tantalum with synchrotron undulator sources

2018 ◽  
Vol 25 (3) ◽  
pp. 748-756 ◽  
Author(s):  
M. X. Tang ◽  
Y. Y. Zhang ◽  
J. C. E ◽  
S. N. Luo
Keyword(s):  
Single Crystal ◽  
Large Scale ◽  
Incident Beam ◽  
Wave Structure ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Diffraction Patterns ◽  
Case Transmission ◽  
Dynamics Simulations

Polychromatic synchrotron undulator X-ray sources are useful for ultrafast single-crystal diffraction under shock compression. Here, simulations of X-ray diffraction of shock-compressed single-crystal tantalum with realistic undulator sources are reported, based on large-scale molecular dynamics simulations. Purely elastic deformation, elastic–plastic two-wave structure, and severe plastic deformation under different impact velocities are explored, as well as an edge release case. Transmission-mode diffraction simulations consider crystallographic orientation, loading direction, incident beam direction, X-ray spectrum bandwidth and realistic detector size. Diffraction patterns and reciprocal space nodes are obtained from atomic configurations for different loading (elastic and plastic) and detection conditions, and interpretation of the diffraction patterns is discussed.

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