A new CuKα2-elimination algorithm

1999 ◽  
Vol 32 (2) ◽  
pp. 168-173 ◽  
Author(s):  
C. Dong ◽  
H. Chen ◽  
F. Wu
Keyword(s):  
Experimental Data ◽  
Powder Diffraction ◽  
Present Method ◽  
Double Crystal ◽  
X Ray ◽  
Emission Profile ◽  
Elimination Algorithm ◽  
First Category ◽  
Diffraction Patterns ◽  
Second Category

This paper presents a new algorithm to remove the CuKα2profile in X-ray powder diffraction patterns. Previous algorithms for α2elimination can be divided into two categories. The first category assumes the shape identity of the α1and α2components. The second category uses parameters by fitting experimental data. The first category is not accurate and the second one is instrument-dependent. The algorithm presented here uses the CuKα emission profile obtained from monolithic double-crystal measurements. Therefore, it is more accurate and less instrument-dependent than the previous methods. This algorithm has been tested and applied in software for diffraction data processing. The present method can be extended to removeKα2lines of other radiations.

Phonons and Crystalline Structure of Hg1−xCdxS e Alloys (0 < x ≤ 0.5)

2012 ◽  
Vol 1372 ◽  
Author(s):  
David A. Miranda ◽  
S. A. López-Rivera ◽  
Ch. Power ◽  
J. A. Henao ◽  
M. A. Macías
Keyword(s):  
Experimental Data ◽  
Raman Spectroscopy ◽  
Powder Diffraction ◽  
Molar Fraction ◽  
Face Centered Cubic ◽  
X Ray ◽  
Cell Parameters ◽  
Cubic Structure ◽  
Diffraction Patterns ◽  
Face Centered

ABSTRACTPhonons and crystalline structures of Hg1−xCdxSe alloys (0 ≤ x ≤ 0.5) were studied by Raman spectroscopy and X-ray powder diffraction patterns at 298K. The crystalline alloys were prepared by a special combination of synthesis and the Bridgman method. Experimental data showed a face-centered cubic structure, $F\overline 4 \,3\,m$ (No. 216), for all samples, exhibiting a linear dependence for Cd molar fraction, x, for cell parameters, a, and the mass densities, ρ. Phonon frequencies were analyzed using the Romevi-Romevi model for phonons in multicomponent alloys, obtaining a fair agreement with experimental data. Furthermore, an algorithm to implement the Romevi-Romevi model is proposed.

Physico-Chemical Characterization of Some 5,5-Disubstituted-1,3-Dixanthyl Barbituric Acids

1967 ◽  
Vol 21 (4) ◽  
pp. 225-231 ◽  
Author(s):  
B. C. Flann ◽  
J. A. R. Cloutier
Keyword(s):  
Experimental Data ◽  
Powder Diffraction ◽  
Infrared Spectra ◽  
Chemical Characterization ◽  
Melting Points ◽  
X Ray ◽  
Physico Chemical ◽  
Diffraction Patterns ◽  
Derivatives Of

The dixanthyl derivatives of 21 clinically important barbituric acids have been prepared. Melting points, infrared spectra, and x-ray powder-diffraction patterns of the purified compounds are presented. Infrared evidence is used to discuss the position of the linkage between the xanthyl and barbiturate portions of the derivatives. The experimental data should prove of particular value for the microchemical identification of barbiturates.

Deconvolution of instrument andKα2contributions from X-ray powder diffraction patterns using nonlinear least squares with penalties

2018 ◽  
Vol 51 (1) ◽  
pp. 112-123 ◽  
Author(s):  
Alan A. Coelho
Keyword(s):  
Least Squares ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Nonlinear Least Squares ◽  
Penalty Functions ◽  
Instrument Function ◽  
X Ray ◽  
Emission Profile ◽  
Fourier Techniques ◽  
Diffraction Patterns

A new deconvolution method, tolerant of noise and independent of knowing the number of Bragg peaks present, has been developed to deconvolute instrument and emission profile distortions from laboratory X-ray powder diffraction patterns. Removing these distortions produces higher-resolution patterns from which the existence of peaks and their shapes can be better determined. Deconvolution typically comprises the use of the convolution theorem to generate a single aberration from instrument and emission profile aberrations and then the Stokes method to deconvolute the resulting aberration from the measured data. These Fourier techniques become difficult when the instrument function changes with diffraction angle and when the signal-to-noise ratio is low. Instead of Fourier techniques, the present approach uses nonlinear least squares incorporating penalty functions, as implemented in the computer programTOPAS-Academic. Specifically, diffraction peaks are laid down at each data point with peak shapes corresponding to either expected peak shapes or peak shapes narrower than expected; a background function is included. Peak intensities and background parameters are then adjusted to obtain the best fit to the diffraction pattern. Rietveld refinement of the deconvoluted pattern results in background parameters that are near identical to those obtained from Rietveld refinement of the original pattern. Critical to the success of the deconvolution procedure are two penalty functions, one a function of the background parameters and the other a function of the peak intensities. Also of importance is the use of a conjugate gradient solution method for solving the matrix equationAx=b.

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.

Synchrotron X-ray studies of metal-organic framework M2(2,5-dihydroxyterephthalate), M = (Mn, Co, Ni, Zn) (MOF74)

2012 ◽  
Vol 27 (4) ◽  
pp. 256-262 ◽  
Author(s):  
W. Wong-Ng ◽  
J. A. Kaduk ◽  
H. Wu ◽  
M. Suchomel
Keyword(s):  
Powder Diffraction ◽  
Metal Organic Framework ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Lattice Parameter ◽  
X Ray ◽  
Metal Organic ◽  
Sorbent Materials ◽  
Diffraction Patterns ◽  
Unsaturated Metal Sites

M2(dhtp)·nH2O (M = Mn, Co, Ni, Zn; dhtp = 2,5-dihydroxyterephthalate), known as MOF74, is a family of excellent sorbent materials for CO2 that contains coordinatively unsaturated metal sites and a honeycomb-like structure featuring a broad one-dimensional channel. This paper describes the structural feature and provides reference X-ray powder diffraction patterns of these four isostructural compounds. The structures were determined using synchrotron diffraction data obtained at beam line 11-BM at the Advanced Photon Source (APS) in the Argonne National Laboratory. The samples were confirmed to be hexagonal R 3 (No. 148). From M = Mn, Co, Ni, to Zn, the lattice parameter a of MOF74 ranges from 26.131 73(4) Å to 26.5738(2) Å, c from 6.651 97(5) to 6.808 83(8) Å, and V ranges from 3948.08 Å3 to 4163.99 Å3, respectively. The four reference X-ray powder diffraction patterns have been submitted for inclusion in the Powder Diffraction File (PDF).

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.

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