Improvement of deconvolution–convolution treatment of axial-divergence aberration in Bragg–Brentano geometry

2018 ◽  
Vol 33 (2) ◽  
pp. 121-133 ◽  
Author(s):  
Takashi Ida ◽  
Shoki Ono ◽  
Daiki Hattan ◽  
Takehiro Yoshida ◽  
Yoshinobu Takatsu ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Peak Shift ◽  
Powder Diffraction Data ◽  
Shape Parameters ◽  
Improved Method ◽  
One Dimensional ◽  
Diffraction Angle ◽  
Cumulant Analysis ◽  
Best Fit

An improved method to correct observed shift and asymmetric deformation of diffraction peak profile caused by the axial-divergence aberration in Bragg–Brentano geometry is proposed. The method is based on deconvolution–convolution treatment applying scale transform of abscissa, Fourier transform, and cumulant analysis of an analytical model for the axial-divergence aberration. The method has been applied to the powder diffraction data of a standard LaB6 powder (NIST SRM660a) sample, collected with a one-dimensional Si strip detector. The locations, widths and shape of the peaks in the deconvolved–convolved powder diffraction data have been analyzed. The finally obtained whole powder diffraction pattern ranging from 10° to 145° in diffraction angle has been simulated by the Pawley method applying a symmetric Pearson VII peak profile model to each peak with ten background, two peak-shift, three line-width, and two peak-shape parameters, and the Rp value of the best fit has been estimated at 4.4%.

Deconvolution–convolution treatment on powder diffraction data collected with CuKα X-ray and NiKβ filter

2018 ◽  
Vol 33 (2) ◽  
pp. 80-87 ◽  
Author(s):  
Takashi Ida ◽  
Shoki Ono ◽  
Daiki Hattan ◽  
Takehiro Yoshida ◽  
Yoshinobu Takatsu ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Background Intensity ◽  
Intensity Data ◽  
Powder Diffraction Data ◽  
Diffraction Intensity ◽  
Powder Specimen ◽  
One Dimensional ◽  
X Ray ◽  
Strip Detector

A method to remove small CuKβ peaks and step structures caused by NiK-edge absorption as well as CuKα2 sub-peaks from powder diffraction intensity data measured with Cu-target X-ray source and Ni-foil filter is proposed. The method is based on deconvolution–convolution treatment applying scale transform of abscissa, Fourier transform, and a realistic spectroscopic model for the source X-ray. The validity of the method has been tested by analysis of the powder diffraction data of a standard LaB6 powder (NIST SRM660a) sample, collected with the combination of CuKα X-ray source, Ni-foil Kβ filter, flat powder specimen and one-dimensional Si strip detector. The diffraction intensity data treated with the method have certainly shown background intensity profile without CuKβ peaks and NiK-edge step structures.

Microstructure anisotropy in CuO powders

2008 ◽  
Vol 23 (S1) ◽  
pp. S81-S86 ◽  
Author(s):  
A. E. Bianchi ◽  
L. Montenegro ◽  
R. Viña ◽  
G. Punte
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Powder Diffraction Data ◽  
Line Broadening ◽  
Strain Anisotropy ◽  
X Ray ◽  
Milled Sample ◽  
Best Fit ◽  
Voigt Function

An anisotropic line broadening study of CuO is reported. X-ray powder diffraction line width modifications observed are modeled when comparing data coming from (1) commercial analytical grade CuO, (2) energetic ball milling sample for 1 h, and (3) samples prepared by thermally annealing the ball milled sample at various temperatures. X-ray powder diffraction data from commercial and produced samples were analyzed by the Rietveld method using a pseudo-Voigt function. Different assumptions including size and strain anisotropy were tried to improve pattern fitting. An anisotropic strain broadening, modeled using Stephens’ approximation, yielded the best fit, thus indicating that strain anisotropy is the main source of the departure from a smooth function of line broadening as a function of 2θ observed in all samples.

Applications of Whole-Powder-Pattern Fitting Technique in Materials Characterization

1993 ◽  
Vol 37 ◽  
pp. 37-47
Author(s):  
Hideo Toraya
Keyword(s):  
Data Analysis ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Computer Software ◽  
Materials Characterization ◽  
Methodological Aspect ◽  
Powder Pattern ◽  
Powder Diffraction Data ◽  
Best Fit

The development of powder-pattern-fitting techniques greatly changed the methodological aspect of materials characterization using powder diffraction data. Pencil and ruler are going out of use in modern powder data analysis, and present-day materials scientists hit a keyboard and manipulate a mouse of computer for deducing the final parameters of the model, which gives the best fit of calculated pattern to the observed one on a CRT screen. Computer software is now widespread, and the success in materials characterization becomes much dependent on their availability.

Crystal Structure Elucidation of Anhydrous Rb2[Pt(CN)4] from X-Ray Powder Diffraction Data

2005 ◽  
Vol 60 (12) ◽  
pp. 1269-1272 ◽  
Author(s):  
Claus Mühle ◽  
Andrey Karpov ◽  
Martin Jansen
Keyword(s):  
Crystal Structure ◽  
Thermal Analysis ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Elucidation ◽  
Powder Diffraction Data ◽  
One Dimensional ◽  
X Ray ◽  
Linear Chains ◽  
Square Planar

The title compound has been synthesized by metathesis of Ba[Pt(CN)4]·4 H2O with Rb2SO4, in aqueous solution. Its crystal structure was solved from X-ray powder diffraction data using the simulated-annealing approach, and refined by Rietveld’s method. The compound crystallizes in space group Imma, a = 11.1432(2), b = 7.4382(1), c = 11.1896(2) Å, V = 927.45(3) Å3, Z = 4, Rp = 0.0402, Rw = 0.0247 (Nhkl = 173). Square-planar tetracyanoplatinate groups stack in an unprecedented eclipsed conformation, forming one-dimensional linear chains of Pt-atoms with Pt-Pt separations of 3.719 Å . Rb2[Pt(CN)4] was characterized by differential thermal analysis, thermogravimetry and infrared spectroscopy.

Equatorial aberration for powder diffraction data collected by continuous-scan integration of a silicon strip X-ray detector

2021 ◽  
Vol 36 (3) ◽  
pp. 169-175
Author(s):  
Takashi Ida
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Peak Shift ◽  
Two Dimensional ◽  
Peak Shape ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Third Order ◽  
X Ray

The application of continuous-scan integration to collect X-ray diffraction data with a Si strip X-ray detector (CSI-SSXD) introduces additional effects on the peak shift and deformation of peak shape caused by the equatorial aberration. A deconvolutional method to correct the effects of equatorial aberration in CSI-SSXD data is proposed in this study. There are four critical angles related to the effects of spillover of the incident X-ray beam from the specimen face in the CSI-SSXD data. Exact values of cumulants of the equatorial aberration function are efficiently evaluated by 4 × 4 point two-dimensional Gauss–Legendre integral. A naïve two-step deconvolutional method has been applied to remove the effects of the first and third-order cumulants of the equatorial aberration function from the observed CSI-SSXD data. The performance of the algorithm has been tested by analyses of CSI-SSXD data of three LaB6 powder specimens with the widths of 20, 10, and 5 mm, collected with a diffractometer with the goniometer radius of 150 mm.

Re-determining the Nowotny chimney–ladder structure VGe1.82 from powder diffraction data

2005 ◽  
Vol 20 (3) ◽  
pp. 198-202 ◽  
Author(s):  
Hanna Lind ◽  
Magnus Boström
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Powder Diffraction Data ◽  
Ladder Structure ◽  
One Dimensional ◽  
Composite Approach ◽  
The One

The Nowotny chimney–ladder compound VGe1.82 was redetermined from powder diffraction data and modelled with the incommensurately modulated composite approach. The dimensions of the tetragonal unit subcells are a=5.9015(3) Å, cGe=2.6916(2)Å, and cV=4.9080(2)Å and the one-dimensional modulation vectors are qGe=0.45159(1)[001]* and qV=0.17656(1)[001]*. Comparison is made with a previous reported commensurate approximation of the structure with a 31-fold cGe axis.

FIDDLE. Simultaneous Indexing and Structure Solution from Powder Diffraction Data using a Genetic Algorithm and Correlation Functions

2019 ◽  
Author(s):  
Carmen Guguta ◽  
Jan M.M. Smits ◽  
Rene de Gelder
Keyword(s):  
Genetic Algorithm ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Correlation Functions ◽  
Cross Correlation ◽  
Simultaneous Optimization ◽  
Powder Diffraction Data ◽  
Structure Solution ◽  
Matching Technique

A method for the determination of crystal structures from powder diffraction data is presented that circumvents the difficulties associated with separate indexing. For the simultaneous optimization of the parameters that describe a crystal structure a genetic algorithm is used together with a pattern matching technique based on auto and cross correlation functions.<br>

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