Composition of pigments of Santorini frescoes: The Rietveld method as an aid in qualitative phase analysis

2004 ◽  
Vol 19 (2) ◽  
pp. 145-148 ◽  
Author(s):  
Svend Erik Rasmussen ◽  
Sidsel Grundvig ◽  
Walter L. Friedrich
Keyword(s):  
Bronze Age ◽  
Phase Analysis ◽  
Rietveld Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
On Line ◽  
Volcanic Islands ◽  
Line Positions ◽  
Qualitative Phase

Ten fragments of bronze age frescoes from the Greek group of volcanic islands known as Santorini have been examined by powder X-ray diffraction. A qualitative phase analysis based on line positions only was supplemented by the Rietveld method which uses complete diffraction profiles to increase the credibility of the phase analysis.

scholarly journals Psilocybin: crystal structure solutions enable phase analysis of prior art and recently patented examples

2022 ◽  
Vol 78 (1) ◽  
Author(s):  
Alexander M. Sherwood ◽  
Robert B. Kargbo ◽  
Kristi W. Kaylo ◽  
Nicholas V. Cozzi ◽  
Poncho Meisenheimer ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rietveld Refinement ◽  
Phase Analysis ◽  
Density Functional ◽  
Rietveld Method ◽  
Quantitative Phase Analysis ◽  
Published Data ◽  
Dihydrogen Phosphate ◽  
X Ray Diffraction ◽  
X Ray

Psilocybin {systematic name: 3-[2-(dimethylamino)ethyl]-1H-indol-4-yl dihydrogen phosphate} is a zwitterionic tryptamine natural product found in numerous species of fungi known for their psychoactive properties. Following its structural elucidation and chemical synthesis in 1959, purified synthetic psilocybin has been evaluated in clinical trials and has shown promise in the treatment of various mental health disorders. In a recent process-scale crystallization investigation, three crystalline forms of psilocybin were repeatedly observed: Hydrate A, Polymorph A, and Polymorph B. The crystal structure for Hydrate A was solved previously by single-crystal X-ray diffraction. This article presents new crystal structure solutions for the two anhydrates, Polymorphs A and B, based on Rietveld refinement using laboratory and synchrotron X-ray diffraction data, and density functional theory (DFT) calculations. Utilizing the three solved structures, an investigation was conducted via Rietveld method (RM) based quantitative phase analysis (QPA) to estimate the contribution of the three different forms in powder X-ray diffraction (PXRD) patterns provided by different sources of bulk psilocybin produced between 1963 and 2021. Over the last 57 years, each of these samples quantitatively reflect one or more of the hydrate and anhydrate polymorphs. In addition to quantitatively evaluating the composition of each sample, this article evaluates correlations between the crystal forms present, corresponding process methods, sample age, and storage conditions. Furthermore, revision is recommended on characterizations in recently granted patents that include descriptions of crystalline psilocybin inappropriately reported as a single-phase `isostructural variant.' Rietveld refinement demonstrated that the claimed material was composed of approximately 81% Polymorph A and 19% Polymorph B, both of which have been identified in historical samples. In this article, we show conclusively that all published data can be explained in terms of three well-defined forms of psilocybin and that no additional forms are needed to explain the diffraction patterns.

Qualitative and quantitative phase analyses of Pingguo bauxite mineral using X-ray powder diffraction and the Rietveld method

2007 ◽  
Vol 22 (4) ◽  
pp. 300-302 ◽  
Author(s):  
Liangqin Nong ◽  
Xiying Yang ◽  
Lingmin Zeng ◽  
Jingping Liu
Keyword(s):  
Rietveld Refinement ◽  
Phase Analysis ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
X Ray ◽  
Quantitative Phase ◽  
Qualitative And Quantitative ◽  
Refinement Method ◽  
Quantitative Analyses ◽  
Qualitative Phase

X-ray powder diffraction technique and the Rietveld refinement method have been used successfully for the qualitative and quantitative analyses of Pingguo bauxite from Guangxi, China. Qualitative phase analysis shows that the Pingguo bauxite contains diaspore (AlOOH), hematite (Fe2O3), goethite (FeOOH), anatase (TiO2), and kaolinite (Al2(Si2O5)(OH)4). Quantitative Rietveld refinement shows that the weight concentrations of diaspore, goethite, hematite, anatase, and kaolinite for the Pingguo bauxite are 71.9(4)%, 7.0(8)%, 11.3(7)%, 6.5(6)%, and 3.3(9)%, respectively.

Quantitative Phase Analyses of a Slag Using X-Ray Powder Diffraction

2014 ◽  
Vol 881-883 ◽  
pp. 1241-1244
Author(s):  
Wei Jin Zeng ◽  
Chao Zeng ◽  
Wei He
Keyword(s):  
Quantitative Analysis ◽  
Phase Analysis ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Quantitative Phase Analysis ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Quantitative Phase ◽  
Full Profile ◽  
Qualitative Phase

The quantitative phase analyses of a slag have been successfully carried out by using both of the full-profile Rietveld and RIR methods from X-ray powder diffraction data. The qualitative phase analysis indicates that the slag contains mayenite (CaO)12(Al2O3)7, olivine Ca2(SiO4), gehlenite Ca2Al (AlSiO7), lemite Ca2(SiO4) and hibonite CaO(Al2O3)6. The quantitative analysis from Rietveld refinement shows that the weight concentrations of mayenite, olivine, gehlenite, lemite and hibonite for the slag are 48.8(4) wt.%, 32.2(5) wt.%, 11.0(9) wt.%, 6.2(1.1) wt.% and 1.8 (1.2) wt.%, respectively. The quantitative phase analysis results obtained by Rietveld method are more precise then those by RIR method.

Predicting the accuracy of mineral phase analysis by X-ray diffraction using Monte Carlo modelling

2014 ◽  
Vol 29 (S1) ◽  
pp. S102-S106 ◽  
Author(s):  
Joel N. O'Dwyer ◽  
James R. Tickner ◽  
Greg J. Roach
Keyword(s):  
Monte Carlo ◽  
Phase Analysis ◽  
Linear Regression Analysis ◽  
Quantitative Phase Analysis ◽  
X Ray Diffraction ◽  
Diffraction Profile ◽  
Line Energy ◽  
X Ray ◽  
On Line ◽  
Comparison Of The Results

Rapid, on-line measurement of feedstock mineralogy is a highly attractive technology for the mineral processing industry. A Monte Carlo particle transport-based modelling technique has been developed to help design and predict the measurement performance of on-line energy-dispersive X-ray diffraction (EDXRD) analysers. The accuracy of the technique was evaluated by performing quantitative phase analysis on a suite of fifteen synthetic potash ore samples. The diffraction profile of each sample was measured with a laboratory EDXRD analyser and an equivalent profile was simulated in the Monte Carlo package. Linear regression analysis was used to determine the mineral abundances in each sample from both the measured and modelled profiles. Comparison of the results showed that the diffraction profiles and measurement accuracies obtained by simulation agree very well with the measured data.

Rapid qualitative phase analysis in highly textured thin films by x-ray diffraction

2008 ◽  
Vol 79 (4) ◽  
pp. 043904 ◽  
Author(s):  
Cesare Borgia ◽  
Sven Olliges ◽  
Ralph Spolenak
Keyword(s):  
Thin Films ◽  
Phase Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Qualitative Phase

X-ray powder diffraction data of LaNi0.5Ti0.45Co0.05O3, LaNi0.45Co0.05Ti0.5O3, and LaNi0.5Ti0.5O3 perovskites

2021 ◽  
pp. 1-6
Author(s):  
Mariana M. V. M. Souza ◽  
Alex Maza ◽  
Pablo V. Tuza
Keyword(s):  
Crystal Structure ◽  
Rietveld Method ◽  
Pechini Method ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Modified Pechini Method ◽  
Scanning Electron

In the present work, LaNi0.5Ti0.45Co0.05O3, LaNi0.45Co0.05Ti0.5O3, and LaNi0.5Ti0.5O3 perovskites were synthesized by the modified Pechini method. These materials were characterized using X-ray fluorescence, scanning electron microscopy, and powder X-ray diffraction coupled to the Rietveld method. The crystal structure of these materials is orthorhombic, with space group Pbnm (No 62). The unit-cell parameters are a = 5.535(5) Å, b = 5.527(3) Å, c = 7.819(7) Å, V = 239.2(3) Å3, for the LaNi0.5Ti0.45Co0.05O3, a = 5.538(6) Å, b = 5.528(4) Å, c = 7.825(10) Å, V = 239.5(4) Å3, for the LaNi0.45Co0.05Ti0.5O3, and a = 5.540(2) Å, b = 5.5334(15) Å, c = 7.834(3) Å, V = 240.2(1) Å3, for the LaNi0.5Ti0.5O3.

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