Journal ArticleDOI
Powder pattern indexing with the dichotomy method
Ali Boultif,Daniel Louër +1 more
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TLDR
In this article, the DICVOL04 algorithm was extended to include a tolerance to the presence of impurity (or inaccurately measured) diffraction lines, a refinement of the zero-point position, a reviewing of all input lines from the solution found from, generally, the first 20 lines, and a cell analysis, based on the concept of the reduced cell, to identify equivalent monoclinic and triclinic solutions.Abstract:
The efficiency of the successive dichotomy method for powder diffraction pattern indexing [Louer & Louer (1972). J. Appl. Cryst. 5, 271–275] has been proved over more than 30 years of usage. Features implemented in the new version of the computer program DICVOL04 include (i) a tolerance to the presence of impurity (or inaccurately measured) diffraction lines, (ii) a refinement of the `zero-point' position, (iii) a reviewing of all input lines from the solution found from, generally, the first 20 lines, (iv) a cell analysis, based on the concept of the reduced cell, to identify equivalent monoclinic and triclinic solutions, and (v) an optional analysis of input powder data to detect the presence of a significant `zero-point' offset. New search strategies have also been introduced, e.g. each crystal system is scanned separately, within the input volume limits, to limit the risk of missing a solution characterized by a metric lattice singularity. The default values in the input file have been extended to 25 A for the linear parameters and 2500 A3 for the cell volume. The search is carried out exhaustively within the input parameter limits and the absolute error on peak position measurements. Many tests with data from the literature and from powder data of pharmaceutical materials, collected with the capillary technique and laboratory monochromatic X-rays, have been performed with a high success rate, covering all crystal symmetries from cubic to triclinic. Some examples reported as `difficult' cases are also discussed. Additionally, a few recommendations for the correct practice of powder pattern indexing are reported.read more
Citations
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Luminescence properties of Eu2+ - activated alkaline-earth silicon-oxynitride MSi2O2-deltaN2+2/3delta (M = Ca, Sr, Ba) : A promising class of novel LED conversion phosphors
TL;DR: In this article, the luminescence properties of Eu2+-activated alkaline-earth silicon-oxynitrides have been studied in the BaO−SiO2−Si3N4 system, and a new BaSi2O2N2 compound was obtained having the monoclinic structure with lattice parameters.
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References
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Journal ArticleDOI
Ab-initio structure determination of LiSbWO6 by X-ray powder diffraction
TL;DR: In this article, the crystal structure of LiSbWO6 was solved from X-ray powder diffraction data and the structure was refined using Rietveld profile refinement principles.
Journal ArticleDOI
Indexing of powder diffraction patterns for low-symmetry lattices by the successive dichotomy method
A. Boultif,D. Louër +1 more
TL;DR: In this paper, a dichotomy method for indexing powder diffraction patterns for low-symmetry lattices is studied in terms of an optimization of bound relations used in the comparison of observed data with the calculated patterns generated at each level of the analysis.
Journal ArticleDOI
Indexing of powder diffraction patterns by iterative use of singular value decomposition
TL;DR: Comparison with three of the most popular indexing programs, namely ITO, DICVOL91 and TREOR90, has shown that the present method as implemented in the program TOPAS is more successful at indexing simulated data.
Journal ArticleDOI
X-Cell: a novel indexing algorithm for routine tasks and difficult cases
TL;DR: X-Cell as discussed by the authors is a novel indexing algorithm that makes explicit use of systematic absences to search for possible indexing solutions from cells with low numbers of calculated reflections to cells with high numbers of reflections.
Book
Structure determination by X-ray crystallography
Mark Ladd,Rex A. Palmer +1 more
TL;DR: In this article, a preliminary examination of crystal geometry by optical and X-ray methods is presented, showing that the intensity of scattering of XRays by Crystals is relatively low.