WCEN: a computer program for initial processing of fiber diffraction patterns

2006 ◽  
Vol 39 (5) ◽  
pp. 752-756 ◽  
Author(s):  
Wen Bian ◽  
Hong Wang ◽  
Ian McCullough ◽  
Gerald Stubbs
Keyword(s):  
Computer Program ◽  
Single Crystal ◽  
Diffraction Data ◽  
Plant Viruses ◽  
Reciprocal Space ◽  
Parameter Determination ◽  
Input And Output ◽  
Fiber Diffraction ◽  
Diffraction Patterns ◽  
Initial Processing

Processing of fiber diffraction patterns is generally more difficult than for single-crystal patterns, and requires different algorithms and software. The programWCENhas been developed to determine experimental and specimen parameters and to convert diffraction data from detector to reciprocal space, and offers a variety of input and output formats, running under Mac OS X and Linux. The program is described and examples from oriented sols of filamentous plant viruses, illustrating different strategies for parameter determination and refinement, are given.

Refinement of the Ferri- and Paramagnetic Phases of Magnetite from Neutron Multiple Diffraction Data

1998 ◽  
Vol 31 (5) ◽  
pp. 718-725 ◽  
Author(s):  
V. L. Mazzocchi ◽  
C. B. R. Parente
Keyword(s):  
Computer Program ◽  
Single Crystal ◽  
Diffraction Data ◽  
Room Temperature ◽  
Structural Parameters ◽  
Thermal Parameters ◽  
Multiple Diffraction ◽  
Shift Method ◽  
Step Process ◽  
Diffraction Patterns

Structural parameters for the ferrimagnetic and paramagnetic phases of magnetite have been refined from neutron multiple diffraction data. Experimental neutron multiple diffraction patterns were obtained by measuring the 111 primary reflection of a natural single crystal of this compound. Measurements were made at room temperature for the ferrimagnetic phase and at 976 K for the paramagnetic phase. The corresponding simulated patterns have been calculated byMULTI, a computer program for the simulation of neutron multiple diffraction patterns. A step-by-step process was used in the refinements according to the parameter-shift method. Both isotropic and anisotropic thermal parameters were assumed for the temperature factor. Isotropic thermal parameters were considered in two different ways: an overall parameter for all ions in the structure and three different parameters for the three special positions occupied by them in the structure. The best results were found in the refinements with anisotropic thermal parameters. In this case, the values of the profileRfactor found for these refinements were 3.00 and 3.32%, respectively, for the ferrimagnetic and paramagnetic phases.

XPAS: An Interactive Computer Program for Analysis of X-Ray Powder Diffraction Patterns

1992 ◽  
Vol 7 (1) ◽  
pp. 6-10 ◽  
Author(s):  
Balbir Singh ◽  
R.J. Gilkes
Keyword(s):  
Computer Program ◽  
Diffraction Data ◽  
Peak Width ◽  
X Ray Diffraction ◽  
Mineral Research ◽  
X Ray ◽  
Interactive Computer Program ◽  
Input And Output ◽  
Standard Compound ◽  
Diffraction Patterns

AbstractAn interactive computer program to display, process and analyze raw powder X-ray diffraction data is described. The program extensively employs graphic means of input and output with the help of “pop-up” windows and menus. In addition to those tasks that are common to most primary raw data analyzing programs, it performs many functions which are generally assigned to separate secondary programs. These functions include on-screen correction of d-spacing with reference to a standard compound, calculation of peak width and crystallite size, subtraction of patterns for differential X-ray diffraction and unrestricted overlay of patterns. The advantages of an integrated single program to process X-ray diffraction data in mineral research are illustrated and discussed.

scholarly journals Direct mapping of fiber diffraction patterns into reciprocal space

2009 ◽  
Vol 42 (2) ◽  
pp. 295-301 ◽  
Author(s):  
Norbert Stribeck ◽  
Ulrich Nöchel
Keyword(s):  
Direct Method ◽  
Reciprocal Space ◽  
Polymer Materials ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
Direct Mapping ◽  
Fiber Diffraction ◽  
Mapping Parameters ◽  
Diffraction Patterns ◽  
A Direct Method

On the basis of the concept of Polanyi [Z. Phys.(1921),7, 149–180], the mapping of fiber diffraction patterns into reciprocal space is revisited. The result is a set of concise mapping relations that does not contain any approximations. This set permits the design of a direct method that, in principle, does not require refinement of mapping parameters even for patterns of tilted fibers. The method is unsuitable for diffuse scattering patterns. If inaccuracies of two pixels can be tolerated, a pattern is automatically mapped into reciprocal space in real time. The method is proposed for the processing of the extensive sets of patterns that are recorded in time-resolved wide-angle X-ray diffraction investigations of polymer materials.

A program to analyze the distributions of unmeasured reflections

2011 ◽  
Vol 44 (4) ◽  
pp. 865-872 ◽  
Author(s):  
Ludmila Urzhumtseva ◽  
Alexandre Urzhumtsev
Keyword(s):  
Spatial Distribution ◽  
Missing Data ◽  
Computer Program ◽  
Diffraction Data ◽  
Reciprocal Space ◽  
Data Set ◽  
Data Completeness ◽  
Significant Time ◽  
Cumulative Data ◽  
Structure Solution

Crystallographic Fourier maps may contain barely interpretable or non-interpretable regions if these maps are calculated with an incomplete set of diffraction data. Even a small percentage of missing data may be crucial if these data are distributed non-uniformly and form connected regions of reciprocal space. Significant time and effort can be lost trying to interpret poor maps, in improving them by phase refinement or in fighting against artefacts, whilst the problem could in fact be solved by completing the data set. To characterize the distribution of missing reflections, several types of diagrams have been suggested in addition to the usual plots of completeness in resolution shells and cumulative data completeness. A computer program,FOBSCOM, has been developed to analyze the spatial distribution of unmeasured diffraction data, to search for connected regions of unmeasured reflections and to obtain numeric characteristics of these regions. By performing this analysis, the program could help to save time during structure solution for a number of projects. It can also provide information about a possible overestimation of the map quality and model-biased features when calculated values are used to replace unmeasured data.

Update in a Rietveld analysis program for x-ray powder spectro-diffractometry

2003 ◽  
Vol 18 (1) ◽  
pp. 32-35 ◽  
Author(s):  
Yanan Xiao ◽  
Fujio Izumi ◽  
Timothy Graber ◽  
P. James Viccaro ◽  
Dale E. Wittmer
Keyword(s):  
Computer Program ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Analysis ◽  
Anomalous Scattering ◽  
Analysis Program ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Synchrotron Light ◽  
Diffraction Patterns

A computer program for refining anomalous scattering factors using x-ray powder diffraction data was revised on the basis of the latest version of a versatile pattern-fitting system, RIETAN-2000. The effectiveness of the resulting program was confirmed by applying it to simulated and measured powder-diffraction patterns of Mn3O4 taken at a synchrotron light source.

A complex pseudo-decagonal quasicrystal approximant, Al37(Co,Ni)15.5, solved by rotation electron diffraction

2014 ◽  
Vol 47 (1) ◽  
pp. 215-221 ◽  
Author(s):  
Devinder Singh ◽  
Yifeng Yun ◽  
Wei Wan ◽  
Benjamin Grushko ◽  
Xiaodong Zou ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Basic Structure ◽  
Electron Diffraction Data ◽  
Dimensional Electron ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns

Electron diffraction is a complementary technique to single-crystal X-ray diffraction and powder X-ray diffraction for structure solution of unknown crystals. Crystals too small to be studied by single-crystal X-ray diffraction or too complex to be solved by powder X-ray diffraction can be studied by electron diffraction. The main drawbacks of electron diffraction have been the difficulties in collecting complete three-dimensional electron diffraction data by conventional electron diffraction methods and the very time-consuming data collection. In addition, the intensities of electron diffraction suffer from dynamical scattering. Recently, a new electron diffraction method, rotation electron diffraction (RED), was developed, which can overcome the drawbacks and reduce dynamical effects. A complete three-dimensional electron diffraction data set can be collected from a sub-micrometre-sized single crystal in less than 2 h. Here the RED method is applied forab initiostructure determination of an unknown complex intermetallic phase, the pseudo-decagonal (PD) quasicrystal approximant Al37.0(Co,Ni)15.5, denoted as PD2. RED shows that the crystal is F-centered, witha= 46.4,b= 64.6,c= 8.2 Å. However, as with other approximants in the PD series, the reflections with oddlindices are much weaker than those withleven, so it was decided to first solve the PD2 structure in the smaller, primitive unit cell. The basic structure of PD2 with unit-cell parametersa= 23.2,b= 32.3,c= 4.1 Å and space groupPnmmhas been solved in the present study. The structure withc= 8.2 Å will be taken up in the near future. The basic structure contains 55 unique atoms (17 Co/Ni and 38 Al) and is one of the most complex structures solved by electron diffraction. PD2 is built of characteristic 2 nm wheel clusters with fivefold rotational symmetry, which agrees with results from high-resolution electron microscopy images. Simulated electron diffraction patterns for the structure model are in good agreement with the experimental electron diffraction patterns obtained by RED.

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.

FINAX: a computer program for correcting diffraction angles, refining cell parameters and calculating powder patterns

1983 ◽  
Vol 16 (6) ◽  
pp. 651-653 ◽  
Author(s):  
E. R. Hovestreydt
Keyword(s):  
Neutron Diffraction ◽  
Computer Program ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Neutron Diffraction Data ◽  
X Ray ◽  
Cell Parameters ◽  
Theoretical Line ◽  
Diffraction Patterns ◽  
Line Positions

A computer program is described, whose purpose is the refinement of cell parameters from X-ray or neutron diffraction data. It is of particular use when working with powder diffraction patterns, as it has the possibility of (a) correcting the measured diffraction angles from reference reflections and of (b) calculating a theoretical powder diffractogram, including intensities. A minimum of crystallographic information has to be given and input is partially in free format. E.s.d.'s in cell parameters, as well as in the volume, are calculated. It handles α 1−α 2 splitting and calculates, apart from the theoretical line positions, also a more realistic position of where to expect a given reflection on the film.

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.

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