THE RIETVELD STRUCTURE REFINEMENT OF THE WOLLASTONITE-2M CRYSTALS FROM BAITA BIHOR DEPOSIT (ROMANIA) USING X-RAY POWDER DIFFRACTION DATA

2013 ◽  
Author(s):  
Gheorghe-Adrian Branoiu
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Powder Diffraction Data ◽  
X Ray

scholarly journals Pressing the Limits of Rietveld Refinement

1988 ◽  
Vol 41 (2) ◽  
pp. 297 ◽  
Author(s):  
RA Young
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Site Occupancy ◽  
The Other ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Refinement Method

Two examples are given, one with X-ray data and one with netltron data, of the determination of structural detail which appear to be at the edge of current possibility for the Rietveld structure-refinement method. In the first example, 2�2 wt% Sb substituted in CalO(P04)6F2 was located. X-ray powder diffraction data collected with special attention to intensity precision and scale constancy were used. The problem was solved through comparison of intra-sample site-occupancy ratios between Sb-doped and undoped samples. In the second example, high quality, high resolution neutron powder diffraction data were required. The problem was to distinguish between two subtly different models of kaolinite for which the R-weighted-pattern values differed only by 2 or 3 units in the third digit and, particularly, to understand the basis for the consistent programmatic choice of one of the models (PI) over the other. The answer was found in the calculated and 'observed' intensities for (h+ k)-odd reflections; although they were very small, less than 1% of the intensities of the main reflections, many of them were distinctly nonzero. Even though these reflections were not separately observable, because of overlap and small size, they nonetheless correlated with one model sufficiently better than the other to produce the consistent choice.

Structure Refinement of High-Density Polyethylene Using X-Ray Powder Diffraction Data and the Rietveld Method

1995 ◽  
Vol 39 ◽  
pp. 515-521
Author(s):  
Kenneth B. Schwartz ◽  
Robert B. Von Dreele
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
High Density Polyethylene ◽  
Rietveld Method ◽  
Structure Refinement ◽  
High Density ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Voigt Profile ◽  
Full Structure

A full structure analysis of a completely crystallized sample of high-density polyethylene (HDPE) has been achieved using x-ray powder diffraction data collected on a laboratory-based powder diffractometer. The structure refinement is performed using the Rietveld method and includes refinement of the carbon and hydrogen atomic positions and temperature factors. The C-C and C-H bond distances and the C-C-C bond angle along the polyethylene chain have been calculated from the refined atomic positions and are in very good agreement with previous experimental and modelling determinations. Evaluations of the pseudo-Voigt profile parameters for Lorentzian strain broadening and me Scherrer coefficient for Gaussian broadening yield reasonable values for microstrain and particle size for this sample. Refinement of the preferred orientation parameter indicates that the HDPE flakes consist of platy crystals or lamellae that are packed normal to the diffraction vector.

X-Ray Powder Diffraction Data and Crystal Refinement of Ternary Compound Ti4ZrSi3

2020 ◽  
Vol 841 ◽  
pp. 99-102
Author(s):  
Liu Qing Liang ◽  
Yan Ying Wei ◽  
De Gui Li
Keyword(s):  
Ternary Compound ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Structure Type ◽  
Hexagonal Structure ◽  
Powder Diffraction Data ◽  
Tungsten Electrode ◽  
X Ray

Ternary compound Ti4ZrSi3 was prepared by arc melting using a non-consumable tungsten electrode under argon atmosphere, then annealed at 1023K for 30 days, the X-ray powder diffraction data of Ti4ZrSi3 was collected on a Rigaku SmartLab X-ray powder diffractometer. The powder patterns of the compound were indexed and structure refinement by using Rietveld method indicate that the Ti4ZrSi3 compound crystallizes in the hexagonal structure, space group P6/mcm (No.193) with Mn5Si3 structure type, a=b=7.5759(3) Ǻ, c=5.2162(2) Ǻ, V=259.28Ǻ3, Z=2, ρx=4.779g cm-3, the Smith–Snyder FOM F30=148.7(0.0064, 46) and the intensity ratio RIR=1.37. The Rietveld refinement results were Rp = 0.0836, Rwp= 0.1092.

X-Ray Powder Diffraction Data and Crystal Refinement of a New Compound AlCrNi3Pr

2016 ◽  
Vol 850 ◽  
pp. 3-7
Author(s):  
Shu Hui Liu ◽  
Liu Qing Liang ◽  
Chang Sheng Qin ◽  
De Gui Li ◽  
Ling Min Zeng ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Structure Type ◽  
Hexagonal Structure ◽  
Powder Diffraction Data ◽  
Tungsten Electrode ◽  
X Ray ◽  
Diffraction Patterns

Rare earth-transition metal (R-T) intermetallics have been well used because of their excellent properties. The X-ray diffraction patterns of many new phases in the R-T system have not been extensively studied. A new compound AlCrNi3Pr was prepared by arc melting using non-consumable tungsten electrode under argon atmosphere, and then annealed at 1023K for 30 days. The X-ray powder diffraction data of AlCrNi3Pr was collected on a Rigaku SmartLab X-ray powder diffractometer. The powder patterns of the compound were indexed, and the structure refinement by using Rietveld method indicated that the AlCrNi3Pr compound crystallized in the hexagonal structure, space group P6/mmm (No.191) with PrNi5 structure type, a=b=5.0553(9) Ǻ, c=4.0763(6) Ǻ, V=90.22Ǻ3, Z=1, ρx=7.288g cm-3, the Smith–Snyder FOM F30=279.1(0.0044, 32) and the intensity ratio RIR=1.23.

Rietveld refinement of the crystal structures of hexagonal Y6Cr4+xAl43−x (x=2.57) and tetragonal YCr4−xAl8+x (x=1.22)

1995 ◽  
Vol 10 (2) ◽  
pp. 86-90 ◽  
Author(s):  
R. Černý ◽  
K. Yvon ◽  
T. I. Yanson ◽  
M. B. Manyako ◽  
O. I. Bodak
Keyword(s):  
Crystal Structures ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Powder Diffraction Data ◽  
Space Group ◽  
X Ray

Y6Cr4+xAl43−x (x = 2.57); space group P63/mcm, a = 10.8601(1) Å, c = 17.6783(3) Å, V= 1805.7(1) Å3, Z=2; isostructural to Yb6Cr4+xAl43−x, (x=1.76) with two aluminium sites partially occupied by chromium (44% and 27% Cr). YCr4−xAl8+x (x=1.22); space group I4/mmm, a = 9.0299(2) Å, c = 5.1208(2) Å, V=417.55(3) Å3, Z=2, disordered variant of CeMn4Al8 with one chromium site (8f) partially occupied by aluminium (33% Al); X-ray powder diffraction data were collected on a well-crystallized multiphase sample containing 43 wt.% of Y6Cr4+xAl43−x, 27 wt.% of Y2Cr8−xAl16+x, 16 wt.% of Al, 13 wt.% of YAl3, and traces of Y2O3. Structure refinement converged at Rwp = 2.0% and RB = 3.5, 3.6% resp. for a total of 78 parameters and 1190 reflections.

scholarly journals PDFgetX3: a rapid and highly automatable program for processing powder diffraction data into total scattering pair distribution functions

2013 ◽  
Vol 46 (2) ◽  
pp. 560-566 ◽  
Author(s):  
P. Juhás ◽  
T. Davis ◽  
C. L. Farrow ◽  
S. J. L. Billinge
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Academic Research ◽  
Environmental Parameters ◽  
Distribution Functions ◽  
Ease Of Use ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Structure Information

PDFgetX3is a new software application for converting X-ray powder diffraction data to an atomic pair distribution function (PDF).PDFgetX3has been designed for ease of use, speed and automated operation. The software can readily process hundreds of X-ray patterns within a few seconds and is thus useful for high-throughput PDF studies that measure numerous data sets as a function of time, temperature or other environmental parameters. In comparison to the preceding programs,PDFgetX3requires fewer inputs and less user experience and it can be readily adopted by novice users. The live-plotting interactive feature allows the user to assess the effects of calculation parameters and select their optimum values.PDFgetX3uses anad hocdata correction method, where the slowly changing structure-independent signal is filtered out to obtain coherent X-ray intensities that contain structure information. The output fromPDFgetX3has been verified by processing experimental PDFs from inorganic, organic and nanosized samples and comparing them with their counterparts from a previous established software. In spite of the different algorithm, the obtained PDFs were nearly identical and yielded highly similar results when used in structure refinement.PDFgetX3is written in the Python language and features a well documented reusable code base. The software can be used either as a standalone application or as a library of PDF processing functions that can be called from other Python scripts. The software is free for open academic research but requires paid license for commercial use.

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