Local Structure of Si-Al-Ca-Na-O Glasses from Coupled Neutron and X-ray Total Scattering Data

The atomic structure of a spinel-type MgCo2O4 nanoparticle was investigated by the reverse Monte Carlo modelling using X-ray and neutron total scattering data.

Download Full-text

X-ray diffraction, neutron scattering and EXAFS spectroscopy of monoclinic zirconia: analysis by Rietveld refinement and reverse Monte Carlo simulations

Journal of Applied Crystallography ◽

10.1107/s0021889802006829 ◽

2002 ◽

Vol 35 (4) ◽

pp. 434-442 ◽

Cited By ~ 38

Author(s):

Markus Winterer ◽

Robert Delaplane ◽

Robert McGreevy

Keyword(s):

Monte Carlo ◽

Neutron Scattering ◽

Rietveld Refinement ◽

Local Structure ◽

Exafs Spectroscopy ◽

Scattering Data ◽

Accurate Information ◽

Reverse Monte Carlo ◽

Monoclinic Zirconia ◽

X Ray

Extended X-ray absorption fine structure (EXAFS) and neutron scattering data from monoclinic zirconia are analysed independently and simultaneously by reverse Monte Carlo (RMC) modelling. X-ray and neutron powder diffraction data are analysed by Rietveld refinement. The results are compared with respect to the local structure around the zirconium cations. Monoclinic zirconia was chosen as a model system for the comparison of structural information obtained by EXAFS spectroscopy and scattering methods because it is crystalline but also has some local disorder. In the case of zirconia, analysis of EXAFS spectra by RMC modelling results in reliable and accurate information on the local structure, consistent with neutron scattering and diffraction experiments.

Download Full-text

xINTERPDF: a graphical user interface for analyzing intermolecular pair distribution functions of organic compounds from X-ray total scattering data

Journal of Applied Crystallography ◽

10.1107/s1600576718012359 ◽

2018 ◽

Vol 51 (5) ◽

pp. 1498-1499

Author(s):

Chenyang Shi

Keyword(s):

User Interface ◽

Organic Compounds ◽

Graphical User Interface ◽

Distribution Functions ◽

Scattering Data ◽

Total Scattering ◽

X Ray ◽

Software Program ◽

Pair Distribution Functions

A new software program, xINTERPDF, that analyzes the intermolecular correlations in organic compounds via measured X-ray total scattering data is described.

Download Full-text

Local Structure of Ba1–xSrxTiO3and BaTi1–yZryO3Nanocrystals Probed by X-ray Absorption and X-ray Total Scattering

ACS Nano ◽

10.1021/nn405629e ◽

2013 ◽

Vol 7 (12) ◽

pp. 11435-11444 ◽

Cited By ~ 14

Author(s):

Federico A. Rabuffetti ◽

Richard L. Brutchey

Keyword(s):

Local Structure ◽

Total Scattering ◽

X Ray ◽

X Ray Absorption

Download Full-text

Comparison of total scattering data from various sources: the case of a nanometric spinel

Powder Diffraction ◽

10.1017/s0885715614001389 ◽

2015 ◽

Vol 30 (S1) ◽

pp. S65-S69 ◽

Cited By ~ 10

Author(s):

Giorgia Confalonieri ◽

Monica Dapiaggi ◽

Marco Sommariva ◽

Milen Gateshki ◽

Andy N. Fitch ◽

...

Keyword(s):

High Resolution ◽

High Energy ◽

European Synchrotron Radiation Facility ◽

Distribution Functions ◽

Scattering Data ◽

Data Set ◽

Total Scattering ◽

X Ray ◽

Fair Comparison ◽

Pair Distribution Functions

Total scattering data of nanocrystalline gahnite (ZnAl2O4, 2–3 nm) have been collected with three of the most commonly used instruments: (i) ID31 high-resolution diffractometer at the European Synchrotron Radiation Facility (ESRF) (Qmax = 22 Å−1); (ii) ID11 high-energy beamline at the ESRF (Qmax = 26.6 Å−1); and (iii) Empyrean laboratory diffractometer by PANalytical with molybdenum anode X-ray tube (Qmax = 17.1 Å−1). Pair distribution functions (PDFs) for each instrument data-set have been obtained, changing some of the parameters, by PDFgetX3 software, with the aim of testing the software in the treatment of different total scattering data. The material under analysis has been chosen for its nanometric (and possibly disordered) nature, to give rise to a challenge for all the diffractometers involved. None of the latter should have a clear advantage. The PDF and F(Q) functions have been visually compared, and then the three PDF sets have been used for refinements by means of PDFgui suite. All the refinements have been made exactly in the same way for the sake of a fair comparison. Small differences could be observed in the experimental PDFs and the derived results, but none of them seemed to be significant.

Download Full-text

Local Structure of Iridate Pyrochlores from Hydrothermal Synthesis

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s205327331409130x ◽

2014 ◽

Vol 70 (a1) ◽

pp. C869-C869

Author(s):

Helen Playford ◽

Ravi SINGH ◽

Lieh Jeng Chang ◽

Kripasindhu Sardar ◽

Alex Hannon ◽

...

Keyword(s):

Local Structure ◽

Synthesis Method ◽

Pyrochlore Structure ◽

Magnetic Ordering ◽

Structural Disorder ◽

Lattice Parameter ◽

Magnetic Behaviour ◽

Total Scattering ◽

X Ray ◽

Cation Content

Iridate pyrochlores of general formula M2Ir2O7have potential applications in catalysis [1]. They also often exhibit unusual magnetic and electronic properties caused by spin-orbit coupling and geometric frustration [2]. A detailed understanding of structure is necessary to enable these properties to be understood and exploited. Because of the propensity of the pyrochlore structure to accommodate structural disorder, we have chosen to utilise the technique of total scattering to examine the structure of M2Ir2O7(M = Bi, Nd). The sensitivity of our measurements to all the constituent elements is maximised by the combination of both neutron and X-ray total scattering. We find no evidence for magnetic ordering in our samples of Nd2Ir2O7, in contrast to literature reports [3]. By comparing the local structure of our samples with that of one reported to exhibit magnetic ordering, we explore the possibility of a structural origin for the differences in magnetic behaviour. We have found that synthesis method can directly influence the structure of these iridate pyrochlores. Local structural analysis provides evidences of A-site cation deficiency and partial oxidation of Ir(IV) to Ir(V) in samples produced by hydrothermal techniques. Irreversible changes to the lattice parameter upon heating these samples at 400 – 9000C further support the inference that the cation content is somewhat variable. We report the results of reverse Monte Carlo (RMC) refinements using the program RMCProfile, which is capable of simultaneously fitting to X-ray and neutron data, and therefore provides structural models of the greatest possible accuracy. We also report the results of in situ X-ray total scattering measurements which provide local-scale insight into the interesting thermal behaviour and apparent flexible cation content of these materials.

Download Full-text

Local and long-range atomic/magnetic structure of non-stoichiometric spinel iron oxide nanocrystallites

IUCrJ ◽

10.1107/s2052252520013585 ◽

2021 ◽

Vol 8 (1) ◽

pp. 33-45

Author(s):

Henrik L. Andersen ◽

Benjamin A. Frandsen ◽

Haraldur P. Gunnlaugsson ◽

Mads R. V. Jørgensen ◽

Simon J. L. Billinge ◽

...

Keyword(s):

Iron Oxide ◽

Magnetic Nanoparticles ◽

Iron Oxide Nanoparticles ◽

Structural Characterization ◽

Magnetic Domain ◽

Scattering Data ◽

Oxide Nanoparticles ◽

Total Scattering ◽

X Ray ◽

Neutron Total Scattering

Spinel iron oxide nanoparticles of different mean sizes in the range 10–25 nm have been prepared by surfactant-free up-scalable near- and super-critical hydrothermal synthesis pathways and characterized using a wide range of advanced structural characterization methods to provide a highly detailed structural description. The atomic structure is examined by combined Rietveld analysis of synchrotron powder X-ray diffraction (PXRD) data and time-of-flight neutron powder-diffraction (NPD) data. The local atomic ordering is further analysed by pair distribution function (PDF) analysis of both X-ray and neutron total-scattering data. It is observed that a non-stoichiometric structural model based on a tetragonal γ-Fe2O3 phase with vacancy ordering in the structure (space group P43212) yields the best fit to the PXRD and total-scattering data. Detailed peak-profile analysis reveals a shorter coherence length for the superstructure, which may be attributed to the vacancy-ordered domains being smaller than the size of the crystallites and/or the presence of anti-phase boundaries, faulting or other disorder effects. The intermediate stoichiometry between that of γ-Fe2O3 and Fe3O4 is confirmed by refinement of the Fe/O stoichiometry in the scattering data and quantitative analysis of Mössbauer spectra. The structural characterization is complemented by nano/micro-structural analysis using transmission electron microscopy (TEM), elemental mapping using scanning TEM, energy-dispersive X-ray spectroscopy and the measurement of macroscopic magnetic properties using vibrating sample magnetometry. Notably, no evidence is found of a Fe3O4/γ-Fe2O3 core-shell nanostructure being present, which had previously been suggested for non-stoichiometric spinel iron oxide nanoparticles. Finally, the study is concluded using the magnetic PDF (mPDF) method to model the neutron total-scattering data and determine the local magnetic ordering and magnetic domain sizes in the iron oxide nanoparticles. The mPDF data analysis reveals ferrimagnetic collinear ordering of the spins in the structure and the magnetic domain sizes to be ∼60–70% of the total nanoparticle sizes. The present study is the first in which mPDF analysis has been applied to magnetic nanoparticles, establishing a successful precedent for future studies of magnetic nanoparticles using this technique.

Download Full-text