16,735 research outputs found
Parametric Rietveld refinement
In this paper the method of parametric Rietveld refinement is described, in which an ensemble of diffraction data collected as a function of time, temperature, pressure or any other variable are fitted to a single evolving structural model. Parametric refinement offers a number of potential benefits over independent or sequential analysis. It can lead to higher precision of refined parameters, offers the possibility of applying physically realistic models during data analysis, allows the refinement of `non-crystallographic' quantities such as temperature or rate constants directly from diffraction data, and can help avoid false minima
Crystallite Size Effect on Lattice Strain and Crystal Structure of Ba1/4Sr3/4MnO3 Layered Perovskite Manganite
The single phase polycrystalline Ba1/4Sr3/4MnO3 layered perovskite manganite
has been synthesized by combustion method having various crystallite sizes. The
room temperature X-ray diffraction patterns reveal that Ba1/4Sr3/4MnO3
crystallizes into hexagonal crystal structure with space group P63/mmc as
confirmed by Rietveld refinement. The scanning electron micrographs of
Ba1/4Sr3/4MnO3 reveal uniform crystallite size of the samples. Effect of
crystallite size on lattice strain and crystal structure has been studied using
Rietveld refinement and Williamson-Hall plot, respectively. The structural
lattice parameters decrease with increasing crystallite size. However, lattice
strain increases with increasing crystallite-size
Rietveld refinement of Y2GeO5
Y2GeO5 (yttrium germanium pentaÂoxide) was synthesized by solid-state reaction at 1443 K. The arrangement, which has monoclinic symmetry, is isostructural with Dy2GeO5 and presents two independent sites for the Y atoms. Around these atoms there are distorted six-coordinated YO6 octaÂhedra and seven-coordinated YO7 pentaÂgonal bipyramids. The YO7 polyhedra are linked together, sharing their edges along a surface parallel to ab, forming a sheet. Each of these parallel sheets is interÂconnected by means of GeO4 tetraÂhedra, sharing an edge (or vertex) on one side and a vertex (or edge) on the other adjacent side. Parallel sheets of YO7 polyhedra are also interÂconnected by undulating chains of YO6 octaÂhedra along the c axis. These octaÂhedra are joined together, sharing a common edge, to form the chain and share edges with the YO7 polyhedra of the sheets
X-ray Diffraction Analysis of Cu2+ Doped Zn1-xCuxFe2O4 Spinel Nanoparticles using Williamson-Hall Plot Method
The nanoparticles (NPs) of Zn1-xCuxFe2O4 (ZCFO) spinels with x = 0, 0.2, 0.4,
0.6 and 0.8 were synthesized by a sol-gel combustion method using acetate
precursor. The NPs of ZCFO were prepared by following calcination process at
600C for 8hrs. The synthesized NPs of ZCFO were characterized by X-ray
diffraction (XRD) analysis using Rietveld refinement. The Rietveld refinement
of the XRD patterns revealed that the ZCFO spinels crystallize into single
diamond cubic structure with Fd-3m space group. The lattice constant and unit
cell volume for ZCFO NPs shrink with enhancing doping concentration of Cu2+
ion. The crystalline growth in the NPs of ZCFO was examined by peak broadening
present in the XRD pattern. The Williamson-Hall (W-H) plot method were used to
study the individual involvements of crystallite sizes and lattice strain on
the peak broadening of the NPs of ZCFO spinels. Whereas, particle size of the
ZCFO sample with x = 0.40 was estimated by high-resolution scanning electron
microscopy micrograph
Structural study of CuSe alloys produced by mechanical alloying
The crystalline structures of superionic high temperature copper selenides
CuSe () produced by Mechanical Alloying were
investigated using X-ray diffraction (XRD) technique. The measured XRD patterns
showed the presence of the peaks corresponding to the crystalline superionic
high temperature -CuSe phase in the as-milled sample, and its
structural data were determined by means of a Rietveld refinement procedure.
After a heat treatment in argon at 200C for 90 h, this phase transforms
to the superionic high temperature -CuSe phase, whose
structural data where also determined through the Rietveld refinement. In this
phase, a very low occupation of the trigonal 32(f) sites (%) by Cu ions
is found. In order to explain the evolution of the phases in the samples, two
possible mechanisms are suggested: the high mobility of Cu ions in superionic
phases and the intense diffusive processes in the interfacial component of
samples produced by Mechanical Alloying.Comment: 2 figures, submitted to Acta Crystallographic
AutoFP: a GUI for highly automated Rietveld refinement using an expert system algorithm based on FullProf
AutoFP, a highly automated software toolkit, has been developed to improve the extent of automation of the widely used Rietveld refinement program FullProf [RodrÃguez-Carvajal (1993). Physica B, 192, 55-69]. An expert system algorithm is used as the control layer to simulate the manual process when FullProf is used to perform Rietveld refinement. This enables the program to complete the Rietveld refinement highly automatically. It is shown that the expert system algorithm is a good choice for automating Rietveld refinement. The programming interface is available for advanced users to implement their own acquired experience of refinement or add new Rietveld refinement engines to AutoFP. AutoFP can be also used as an automated Rietveld refinement engine by other programs. AutoFP is an open-source software package developed in Python, and it is user friendly, easy to learn and easy to use
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