Simultaneous reverse Monte Carlo refinements of local structures in perovskite solid solutions using EXAFS and the total scattering pair-distribution function

2008 ◽  
Vol 41 (4) ◽  
pp. 705-714 ◽  
Author(s):  
Victor Krayzman ◽  
Igor Levin ◽  
Mathew G. Tucker
Keyword(s):  
Monte Carlo ◽  
Distribution Function ◽  
Solid Solutions ◽  
Pair Distribution Function ◽  
Computer Software ◽  
Real Space ◽  
Reverse Monte Carlo ◽  
Total Scattering ◽  
X Ray ◽  
Local Structures

Reverse Monte Carlo (RMC) refinements using a combined real-space fit of the neutron/X-ray total scattering pair-distribution function (PDF) and the extended X-ray absorption fine structure (EXAFS) were developed and implemented as an extension to the public domain computer softwareRMCProfile. The effectiveness of combined PDF/EXAFS RMC refinements was tested using perovskite Ca(Zr,Ti)O3solid solutions. The analyses revealed that combining two types of data yields correct distributions of the Ti—O and Zr—O distances that could not be recovered using either of the techniques alone because of the substantial overlap between the Ti—O and Zr—O partial PDFs. The combined refinements enabled reasonably accurate reproduction of most of the local structure characteristics, including the dependence of Ca displacements on the localB-cation coordination around Ca.

scholarly journals A simple correction for the parallax effect in X-ray pair distribution function measurements

2019 ◽  
Vol 52 (5) ◽  
pp. 1072-1076 ◽  
Author(s):  
Frederick Marlton ◽  
Oleh Ivashko ◽  
Martin v. Zimmerman ◽  
Olof Gutowski ◽  
Ann-Christin Dippel ◽  
...  
Keyword(s):  
Distribution Function ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Pair Distribution Function ◽  
Reference Data ◽  
Real Space ◽  
X Ray ◽  
Local Structures ◽  
Pdf Analysis ◽  
Complex Nanostructures

Total scattering and pair distribution function (PDF) analysis has created new insights that traditional powder diffraction methods have been unable to achieve in understanding the local structures of materials exhibiting disorder or complex nanostructures. Care must be taken in such analyses as subtle and discrete features in the PDF can easily be artefacts generated in the measurement process, which can result in unphysical models and interpretation. The focus of this study is an artefact called the parallax effect, which can occur in area detectors with thick detection layers during the collection of X-ray PDF data. This effect results in high-Q peak offsets, which subsequently cause an r-dependent shift in the PDF peak positions in real space. Such effects should be accounted for if a truly accurate model is to be achieved, and a simple correction that can be conducted via a Rietveld refinement against the reference data is proposed.

Real-Space X-Ray Pair Distribution Function Analysis and Molecular-Dynamics Modelling of Diflunisal Channel Hydrates

2020 ◽  
Author(s):  
Anuradha Pallipurath ◽  
Francesco Civati ◽  
Jonathan Skelton ◽  
Dean Keeble ◽  
Clare Crowley ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Distribution Function ◽  
Structural Dynamics ◽  
First Principles ◽  
Pair Distribution Function ◽  
Function Analysis ◽  
Real Space ◽  
X Ray ◽  
Dynamics Modelling ◽  
Dynamics Simulations

X-ray pair distribution function analysis is used with first-principles molecular dynamics simulations to study the co-operative H<sub>2</sub>O binding, structural dynamics and host-guest interactions in the channel hydrate of diflunisal.

Oxygen Vacancy Distribution and Electron Localization on Nanocube CeO2(100)

2021 ◽  
Author(s):  
Weihua Ji ◽  
Na Wang ◽  
Qiang Li ◽  
He Zhu ◽  
Kun Lin ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Distribution Function ◽  
Pair Distribution Function ◽  
Oxygen Vacancies ◽  
Electron Localization ◽  
Reverse Monte Carlo ◽  
Atomic Pair Distribution Function ◽  
Atomic Pair ◽  
Vacancy Distribution ◽  
Neutron Total Scattering

In this work, the oxygen vacancies distribution in the 5nm CeO2 nanocubes was determined by Reverse Monte Carlo (RMC) simulations for the neutron total scattering atomic pair distribution function (PDF)...

scholarly journals The atomic structure of a MgCo2O4 nanoparticle for a positive electrode of a Mg rechargeable battery

2019 ◽  
Vol 55 (17) ◽  
pp. 2517-2520 ◽  
Author(s):  
Naoto Kitamura ◽  
Yuhei Tanabe ◽  
Naoya Ishida ◽  
Yasushi Idemoto
Keyword(s):  
Monte Carlo ◽  
Atomic Structure ◽  
Positive Electrode ◽  
Scattering Data ◽  
Rechargeable Battery ◽  
Reverse Monte Carlo ◽  
Spinel Type ◽  
Total Scattering ◽  
X Ray ◽  
Neutron Total Scattering

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.

scholarly journals Precise implications for real-space pair distribution function modeling of effects intrinsic to modern time-of-flight neutron diffractometers

2018 ◽  
Vol 74 (4) ◽  
pp. 293-307 ◽  
Author(s):  
Daniel Olds ◽  
Claire N. Saunders ◽  
Megan Peters ◽  
Thomas Proffen ◽  
Joerg Neuefeind ◽  
...  
Keyword(s):  
Distribution Function ◽  
Pair Distribution Function ◽  
Amorphous Materials ◽  
Best Practice ◽  
Time Of Flight ◽  
Real Space ◽  
Mitigation Strategies ◽  
Total Scattering ◽  
Conventional Analysis ◽  
Pdf Analysis

Total scattering and pair distribution function (PDF) methods allow for detailed study of local atomic order and disorder, including materials for which Rietveld refinements are not traditionally possible (amorphous materials, liquids, glasses and nanoparticles). With the advent of modern neutron time-of-flight (TOF) instrumentation, total scattering studies are capable of producing PDFs with ranges upwards of 100–200 Å, covering the correlation length scales of interest for many materials under study. Despite this, the refinement and subsequent analysis of data are often limited by confounding factors that are not rigorously accounted for in conventional analysis programs. While many of these artifacts are known and recognized by experts in the field, their effects and any associated mitigation strategies largely exist as passed-down `tribal' knowledge in the community, and have not been concisely demonstrated and compared in a unified presentation. This article aims to explicitly demonstrate, through reviews of previous literature, simulated analysis and real-world case studies, the effects of resolution, binning, bounds, peak shape, peak asymmetry, inconsistent conversion of TOF to d spacing and merging of multiple banks in neutron TOF data as they directly relate to real-space PDF analysis. Suggestions for best practice in analysis of data from modern neutron TOF total scattering instruments when using conventional analysis programs are made, as well as recommendations for improved analysis methods and future instrument design.

scholarly journals Total-scattering pair-distribution function analysis of zinc from high-energy synchrotron data

2019 ◽  
Vol 33 (33) ◽  
pp. 1950410 ◽  
Author(s):  
Ahmad S. Masadeh ◽  
Moneeb T. M. Shatnawi ◽  
Ghosoun Adawi ◽  
Yang Ren
Keyword(s):  
Crystal Structure ◽  
Distribution Function ◽  
Pair Distribution Function ◽  
Function Analysis ◽  
High Energy ◽  
Ambient Conditions ◽  
Total Scattering ◽  
X Ray ◽  
Zinc Metal ◽  
Pdf Analysis

The crystal structure of zinc metal deviates from the ideal hexagonal close packing structure by a significantly increased axial ratio (c/a). The local atomic structure of zinc metal is investigated using the total scattering atomic pair distribution function (PDF) analysis based on X-ray powder diffraction data collected at ambient conditions. The X-ray total scattering PDF analysis confirms that the crystal structure of zinc can be described in terms of wurtzite structure, but with an anomalously atomic displacement parameters [Formula: see text], indicating a significant displacement disorder along the [Formula: see text]-axis. For the long [Formula: see text]-range PDF refinements, the thermal motion of zinc shows a notable anisotropy as expressed by the ratio [Formula: see text]/[Formula: see text] of 2.5 at ambient conditions. This average distortion level along the [Formula: see text]-axis, was not reflected locally for the features below 5.0 Å as it fits the high [Formula: see text] region. Based on PDF refinements over different [Formula: see text]-ranges, we measure an interesting increase of the [Formula: see text] value with decreasing the [Formula: see text]-range of the refinement. This suggests that the local structure features in zinc metal differ from the average structure ones.

scholarly journals Exploring the origins of crystallisation kinetics in hierarchical materials using in situ X-ray diffraction and pair distribution function analysis

2020 ◽  
Vol 22 (34) ◽  
pp. 18860-18867 ◽  
Author(s):  
Matthew E. Potter ◽  
Mark E. Light ◽  
Daniel J. M. Irving ◽  
Alice E. Oakley ◽  
Stephanie Chapman ◽  
...  
Keyword(s):  
Distribution Function ◽  
Pair Distribution Function ◽  
Function Analysis ◽  
X Ray Diffraction ◽  
Crystallisation Kinetics ◽  
Total Scattering ◽  
Hierarchically Porous ◽  
X Ray ◽  
Scattering Measurements

Novel in situ synchrotron total scattering measurements probe the assembly of primary building units into templated hierarchically porous aluminophosphate catalysts, providing unique insights to understanding crystallisation kinetics.

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