Decomposition of overlapping peaks in X‐ray fluorescence using improved crow searching algorithm based on opposite learning

2021 ◽  
Author(s):  
Xueliang Zhao ◽  
Shicheng Sun ◽  
Meijie Li ◽  
Jie Zhang ◽  
Kang Li ◽  
...  
Keyword(s):  
X Ray ◽  
Overlapping Peaks

scholarly journals Monitoring protein precipitates by in-house X-ray powder diffraction

2013 ◽  
Vol 28 (S2) ◽  
pp. S458-S469 ◽  
Author(s):  
Kenny Ståhl ◽  
Christian G. Frankær ◽  
Jakob Petersen ◽  
Pernille Harris
Keyword(s):  
Powder Diffraction ◽  
Protein Crystal ◽  
Data Sets ◽  
Crystal Forms ◽  
X Ray ◽  
Cell Parameters ◽  
X Ray Scattering ◽  
Source Organism ◽  
Peak Asymmetry ◽  
Overlapping Peaks

Powder diffraction from protein powders using in-house diffractometers is an effective tool for identification and monitoring of protein crystal forms and artifacts. As an alternative to conventional powder diffractometers a single crystal diffractometer equipped with an X-ray micro-source can be used to collect powder patterns from 1 µl samples. Using a small-angle X-ray scattering (SAXS) camera it is possible to collect data within minutes. A streamlined program has been developed for the calculation of powder patterns from pdb-coordinates, and includes correction for bulk-solvent. A number of such calculated powder patterns from insulin and lysozyme have been included in the powder diffraction database and successfully used for search-match identification. However, the fit could be much improved if peak asymmetry and multiple bulk-solvent corrections were included. When including a large number of protein data sets in the database some problems can be foreseen due to the large number of overlapping peaks in the low-angle region, and small differences in unit cell parameters between pdb-data and powder data. It is suggested that protein entries are supplied with more searchable keywords as protein name, protein type, molecular weight, source organism etc. in order to limit possible hits.

Experimental Evaluation of Peak Height Approximation for X-Ray Diffracted Integrated Intensity Method

1980 ◽  
Vol 24 ◽  
pp. 277-282
Author(s):  
Charles P. Gazzara
Keyword(s):  
Mathematical Description ◽  
Experimental Evaluation ◽  
Polycrystalline Material ◽  
Peak Height ◽  
Diffraction Peak ◽  
Characteristic Peak ◽  
Practical Solution ◽  
X Ray ◽  
Integrated Intensity ◽  
Overlapping Peaks

The mathematical description of an X-ray peak, diffracted from a powder or polycrystalline material, using physically meaningful parameters has been of interest for many years. With the popularity of computers, this need to characterize a diffraction peak has intensified.A key problem which persists is how to describe the instrumental diffracted profile and therefore the observed diffracted characteristic peak with subsequent combinations of Kα doublets and mixed overlapping peaks. Many attempts have been made at finding a “true“ function to fit the observed diffracted peak; however, a practical solution has yet to be found.

X-ray Diffractometric Determination of Lattice Misfit Between γ and γ' Phases in Ni-Base Superalloys

1988 ◽  
Vol 32 ◽  
pp. 365-375 ◽  
Author(s):  
Katsumi Ohno ◽  
Hirosi Harada ◽  
Toshihiro Yamagata ◽  
Michio Yamazaki ◽  
Kazumasa Ohsumi
Keyword(s):  
Lattice Misfit ◽  
Least Square Method ◽  
Least Square ◽  
X Rays ◽  
Deconvolution Method ◽  
X Ray ◽  
Window Functions ◽  
Profile Fitting ◽  
Overlapping Peaks

AbstractThe lattice misfits between γ and γ' phases in Ni-base superalloys (single crystal) were accurately determined for filings of specimens by using both a conventional X-ray tube focusing diffractometer(CXRFD) and a synchrotron-radiation parallel beam X-ray diffractometer (SRPXRD). All reflection peaks measured with the CXRFD were in a cluster of overlapping peaks because of the very small differences in the lattice parameters of both phases and the instrumental broadening due to X-ray optics including the spectral distribution of Xray source such as CuKα doublet. The deconvolution method was applied to remove the instrumental broadening from the peaks measured with the CXRFD. The window functions for the deconvolution method were calculated from CuKα doublet reflection of Si standard by a nonlinear least-square method.The instrumental broadening of SRPXRD was much smaller than that of CXRFD since the monochromatic X-rays produced single peak profiles and constant profile shape over a wide 2θ range. A profile fitting with a pseudo-Voigt function was used to determine 2θ angles to 0.0005 deg. for the synchrotron powder data. The peak angle and shape reflected from γ' phases in γ-matrix and those fron electrochemically extracted γ'-phase were significantly different.

The Characterization of Alpha and Intermediate Aluminum Oxide Mixtures by Semi-Automated XRD

1980 ◽  
Vol 24 ◽  
pp. 271-275 ◽  
Author(s):  
John R. Burleson
Keyword(s):  
Aluminum Oxide ◽  
Single Component ◽  
Iterative Technique ◽  
X Ray Diffraction ◽  
Aluminum Oxides ◽  
X Ray ◽  
Overlapping Peaks ◽  
Xrd Patterns

AbstractIntermediate aluminum oxides (aluminas) have broad X-ray diffraction (XRD) peaks. Many of the phases have similar XRD patterns with overlapping of major peaks. To characterize a multi-component alumina mixture several regions of multiple overlapping peaks are examined. Each region is integrated to a single sum without regard for individual peaks. The integrated regions are applied to various ratio functions obtained from single component standards. By using an iterative technique, the functions converge to yield weight fractions for up to six alumina phases.

Intensities of overlapping peaks in X-ray powder diffraction

1981 ◽  
Vol 16 (10) ◽  
pp. 1197-1204
Author(s):  
V. Valvoda ◽  
U. Voland
Keyword(s):  
Powder Diffraction ◽  
X Ray ◽  
Overlapping Peaks

Advances in Texture Analysis from Diffraction Spectra

1997 ◽  
Vol 30 (1) ◽  
pp. 31-42 ◽  
Author(s):  
S. Matthies ◽  
L. Lutteroti ◽  
H. R. Wenk
Keyword(s):  
Neutron Diffraction ◽  
Structure Refinement ◽  
Orientation Distribution ◽  
Diffraction Spectrum ◽  
X Ray ◽  
Pole Figures ◽  
Overlapping Peaks ◽  
Lattice Planes ◽  
Synthetic Calcite ◽  
Low Symmetry

The orientation distribution of a textured polycrystal has been traditionally determined from a few individual pole figures of lattice planes hkl, measured by X-ray or neutron diffraction. A new method is demonstrated that uses the whole diffraction spectrum, rather than extracted peak intensities, by combining ODF calculation with Rietveld crystal structure refinement. With this method, which is illustrated for a synthetic calcite texture, it is possible to obtain quantitative texture information from highly incomplete pole figures and regions of the diffraction spectrum with many overlapping peaks. The approach promises to be advantageous for low-symmetry compounds and composites with complicated diffraction spectra. The method is particularly elegant for time-of-flight neutron diffraction, saving beam time by using small pole-figure regions and many diffractions.

Profile fitting of X-ray diffraction lines and Fourier analysis of broadening

1992 ◽  
Vol 25 (5) ◽  
pp. 559-570 ◽  
Author(s):  
D. Balzar
Keyword(s):  
Length Distribution ◽  
Distribution Functions ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Average Volume ◽  
X Ray ◽  
Profile Fitting ◽  
Overlapping Peaks ◽  
Effective Domain ◽  
Voigt Function

The extraction of pure-specimen X-ray diffraction-line broadening is described using a convolution of the instrumental profile and an exact Voigt function. Real Fourier coefficients were computed from the Cauchy and Gauss integral breadths and were input for Warren–Averbach analysis. Smooth surface-weighted and volume-weighted column-length distribution functions were obtained and errors in root-mean-square strains as well as effective domain sizes were evaluated. The method was applied to two cubic structures with average volume-weighted domain sizes up to 3600 Å as well as patterns of tetragonal and orthorhombic (La, Sr)2CuO4, which exhibit weak line broadenings and highly overlapping reflections. Comparison with the integral-breadth methods is given. Reliability of the method is discussed in the case of a cluster of overlapping peaks.

The Use of Fourier Self-Deconvolution to Resolve Overlapping X-Ray Powder Diffraction Peaks

1989 ◽  
Vol 4 (3) ◽  
pp. 144-151
Author(s):  
Ernest E. Armstrong ◽  
David G. Cameron
Keyword(s):  
Powder Diffraction ◽  
Curve Fitting ◽  
Weight Percent ◽  
Quantitative Information ◽  
X Ray ◽  
Comparison Of Results ◽  
Overlapping Peaks ◽  
Diffraction Peaks

AbstractFourier self-deconvolution has been successfully applied as a means of obtaining semi-quantitative information by resolving the overlapping peaks in X-ray powder diffractograms collected from mixtures of kaolinite and ripidolite. A series of diffractograms were collected from known mixtures of the two minerals. The diffractograms were then processed using Fourier self-deconvolution over a selected range between 23 and 27° 2θ (encompassing the overlapping peaks of kaolinite (002) and ripidolite (004) at 24.85 and 25.13° 2θ, respectively). Once deconvoluted, areas under individual peaks of kaolinite and ripidolite were calculated using curve fitting. The calculated percentage of kaolinite in the mixtures was then plotted versus the true weight percent of kaolinite. The same procedure was conducted on the original diffractograms using only curve fitting without first deconvoluting. A comparison of results shows that, provided the number of peaks are known, both methods give nearly equal results. However, Fourier self-deconvolution, by increasing the resolution, greatly improves the ability to detect overlapping peaks.

A fast methodology to determine the characteristics of thousands of grains using three-dimensional X-ray diffraction. I. Overlapping diffraction peaks and parameters of the experimental setup

2012 ◽  
Vol 45 (4) ◽  
pp. 693-704 ◽  
Author(s):  
Hemant Sharma ◽  
Richard M. Huizenga ◽  
S. Erik Offerman
Keyword(s):  
Data Analysis ◽  
Three Dimensional ◽  
Experimental Setup ◽  
Centre Of Mass ◽  
X Ray Diffraction ◽  
X Ray ◽  
Overlapping Peaks ◽  
Diffraction Peaks ◽  
Mass Position

A data-analysis methodology is presented for the characterization of three-dimensional microstructures of polycrystalline materials from data acquired using three-dimensional X-ray diffraction (3DXRD). The method is developed for 3DXRD microscopy using a far-field detector and yields information about the centre-of-mass position, crystallographic orientation, volume and strain state for thousands of grains. This first part deals with pre-processing of the diffraction data for input into the algorithms presented in the second part [Sharma, Huizenga & Offerman (2012).J. Appl. Cryst.45, 705–718] for determination of the grain characteristics. An algorithm is presented for accurate identification of overlapping diffraction peaks from X-ray diffraction images, which has been an issue limiting the accuracy of experiments of this type. The algorithm works in two stages, namely the identification of overlapping peaks using a seeded watershed algorithm, and then the fitting of the peaks with a pseudo-Voigt shape function to yield an accurate centre-of-mass position and integrated intensity for the peaks. Regions consisting of up to six overlapping peaks can be successfully fitted. Two simulations and an experiment are used to verify the results of the algorithms. An example of the processing of diffraction images acquired in a 3DXRD experiment with a sample consisting of more than 1600 grains is shown. Furthermore, a procedure for the determination of the parameters of the experimental setup (global parameters) without the need for a calibration sample is presented and validated using simulations. This is immensely beneficial for simplifying experiments and the subsequent data analysis.

X-ray powder diffraction analysis of an organic material for nonlinear optics 3-methyl-4-methoxy-4′-nitrostilbene

1997 ◽  
Vol 12 (3) ◽  
pp. 136-137 ◽  
Author(s):  
Zong-ming Jin ◽  
Zheng Jin ◽  
Fang Huang
Keyword(s):  
Powder Diffraction ◽  
Crystal Structure Data ◽  
Powder Diffraction Data ◽  
Nonlinear Optical Material ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Figures Of Merit ◽  
Overlapping Peaks ◽  
Experimental Values

An organic nonlinear optical material, 3-methyl-4-methoxy-4′-nitrostilbene (C16H15NO3), has been characterized by X-ray powder diffraction. Experimental values of 2θ corrected for systematic errors, relative peak intensities, values of d, and the Miller indices of 77 observed reflections with 2θ up to 82° are reported. The powder diffraction data have been evaluated, and the figures-of-merit are reported. The unit cell parameters least-squares refined from 30 non-overlapping peaks of the orthorhombic compound with a Aba2 space group are a=15.7882(3) Å, b=13.4892(4) Å, c=13.3940(2) Å, V=2852.5(4) Å3, Z=8, Dx=1.254 g/cm3. The powder diffraction results are in a agreement with those obtained from single-crystal structure data.

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