The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Simon J L Billinge - One of the best experts on this subject based on the ideXlab platform.
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Atomic Pair Distribution functions (PDFs) from textured polycrystalline samples: fundamentals
arXiv: Materials Science, 2018Co-Authors: Z. Gong, Simon J L BillingeAbstract:Equations for the reduced structure function and atomic Pair Distribution function (PDF) of a textured polycrystalline sample are formulated in terms of the orientational Distribution function (ODF) and the structure function from a single crystallite. This may be used to determine the sample ODF from experimental data when the structure of the reference crystallite is known.
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Magnetic Pair Distribution function analysis: introduction and applications
Acta Crystallographica Section A Foundations and Advances, 2014Co-Authors: Benjamin A. Frandsen, Xiaohao Yang, Simon J L BillingeAbstract:Short-range magnetic correlations play a crucial role in a variety of condensed matter phenomena, yet they remain notoriously difficult to investigate experimentally. Quantitative analysis of the diffuse scattering of neutrons from local magnetic correlations represents a viable but challenging route toward revealing short-range magnetic order in complex materials. Reverse Monte Carlo techniques that iteratively fit randomly generated structural models in momentum space have been used successfully [1], demonstrating that diffuse magnetic scattering can be rich in information. Recently [2], we developed a real-space approach to investigating local magnetic correlations, which we call magnetic Pair Distribution function (mPDF) analysis in analogy to the more familiar atomic Pair Distribution function. This experimentally accessible quantity reveals magnetic correlations directly in real space and places diffuse and Bragg scattering on equal footing, thereby gaining sensitivity to both short- and long-range magnetic order. Here we present the basic theory behind mPDF analysis and provide several examples of its utility using both simulated and experimentally measured data on several interesting magnetic systems, including a canonical antiferromagnetic, a spin glass, and a spin ice. We discuss the potential impact that mPDF methods may have on current and future research interests in magnetism.
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Magnetic Pair Distribution function analysis of local magnetic correlations.
Acta Crystallographica Section A Foundations and Advances, 2013Co-Authors: Benjamin A. Frandsen, Xiaohao Yang, Simon J L BillingeAbstract:The analytical form of the magnetic Pair Distribution function (mPDF) is derived for the first time by computing the Fourier transform of the neutron scattering cross section from an arbitrary collection of magnetic moments. Similar to the atomic Pair Distribution function applied to the study of atomic structure, the mPDF reveals both short-range and long-range magnetic correlations directly in real space. This function is experimentally accessible and yields magnetic correlations even when they are only short-range ordered. The mPDF is evaluated for various example cases to build an intuitive understanding of how different patterns of magnetic correlations will appear in the mPDF.
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Pair Distribution function computed tomography
Nature Communications, 2013Co-Authors: Simon D M Jacques, Marco Di Michiel, Simon A J Kimber, Xiaohao Yang, R J Cernik, Andrew M Beale, Simon J L BillingeAbstract:Determining the nanostructure within complex composites may lead to greater understanding of their properties. Here, the authors demonstrate the application of X-ray atomic Pair Distribution function computed tomography to resolve the physicochemical properties of palladium nanoparticles on an alumina catalyst.
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Pair Distribution function computed tomography.
Nature communications, 2013Co-Authors: Simon D M Jacques, Marco Di Michiel, Simon A J Kimber, Xiaohao Yang, R J Cernik, Andrew M Beale, Simon J L BillingeAbstract:An emerging theme of modern composites and devices is the coupling of nanostructural properties of materials with their targeted arrangement at the microscale. Of the imaging techniques developed that provide insight into such designer materials and devices, those based on diffraction are particularly useful. However, to date, these have been heavily restrictive, providing information only on materials that exhibit high crystallographic ordering. Here we describe a method that uses a combination of X-ray atomic Pair Distribution function analysis and computed tomography to overcome this limitation. It allows the structure of nanocrystalline and amorphous materials to be identified, quantified and mapped. We demonstrate the method with a phantom object and subsequently apply it to resolving, in situ, the physicochemical states of a heterogeneous catalyst system. The method may have potential impact across a range of disciplines from materials science, biomaterials, geology, environmental science, palaeontology and cultural heritage to health.
Thomas Proffen - One of the best experts on this subject based on the ideXlab platform.
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Extracting differential Pair Distribution functions using MIXSCAT
Journal of Applied Crystallography, 2010Co-Authors: Caroline Wurden, Katharine Page, Anna Llobet, Claire E. White, Thomas ProffenAbstract:Differently weighted experimental scattering data have been used to extract partial or differential structure factors or Pair Distribution functions in studying many materials. However, this is not done routinely partly because of the lack of user-friendly software. This paper presentsMIXSCAT, a new member of theDISCUSprogram package.MIXSCATallows one to combine neutron and X-ray Pair Distribution functions and extract their respective differential functions.
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Pair Distribution function and structure factor of spherical particles
Physical Review B, 2006Co-Authors: Rafael C Howell, Thomas Proffen, S D ConradsonAbstract:The availability of neutron spallation-source instruments that provide total scattering powder diffraction has led to an increased application of real-space structure analysis using the Pair Distribution function. Currently, the analytical treatment of finite size effects within Pair Distribution refinement procedures is limited. To that end, an envelope function is derived which transforms the Pair Distribution function of an infinite solid into that of a spherical particle with the same crystal structure. Distributions of particle sizes are then considered, and the associated envelope function is used to predict the particle size Distribution of an experimental sample of gold nanoparticles from its Pair Distribution function alone. Finally, complementing the wealth of existing diffraction analysis, the peak broadening for the structure factor of spherical particles, expressed as a convolution derived from the envelope functions, is calculated exactly for all particle size Distributions considered, and peak maxima, offsets, and asymmetries are discussed.
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Pair Distribution function and structure factor of spherical particles
Physical Review B, 2006Co-Authors: Rafael C Howell, Thomas Proffen, S D ConradsonAbstract:The availability of neutron spallation-source instruments that provide total scattering powder diffraction has led to an increased application of real-space structure analysis using the Pair Distribution function. Currently, the analytical treatment of finite size effects within Pair Distribution refinement procedures is limited. To that end, an envelope function is derived which transforms the Pair Distribution function of an infinite solid into that of a spherical particle with the same crystal structure. Distributions of particle sizes are then considered, and the associated envelope function is used to predict the particle size Distribution of an experimental sample of gold nanoparticles from its Pair Distribution function alone. Finally, complementing the wealth of existing diffraction analysis, the peak broadening for the structure factor of spherical particles, expressed as a convolution derived from the envelope functions, is calculated exactly for all particle size Distributions considered, and peak maxima, offsets, and asymmetries are discussed.Comment: 7 pages, 6 figure
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Obtaining structural information from the atomic Pair Distribution function
Zeitschrift für Kristallographie - Crystalline Materials, 2004Co-Authors: Thomas Proffen, Katharine PageAbstract:The knowledge of the detailed atomic structure of modern materials is the key to understanding the their macroscopic properties. The atomic Pair Distribution function (PDF) reveals short-range and medium-range structural information. In this paper we present an overview of refinement and modelling techniques, In short, we will be trying to answer the question: What can I learn from my PDF?.
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Chemical short range order obtained from the atomic Pair Distribution function
Zeitschrift für Kristallographie - Crystalline Materials, 2002Co-Authors: Thomas Proffen, Simon J L Billinge, Valeri Petkov, Thomas VogtAbstract:Many crystalline materials show chemical short range order and relaxation of neighboring atoms. Lo- cal structural information can be obtained by analyzing the atomic Pair Distribution function (PDF) obtained from powder diffraction data. In this paper, we present the suc- cessful extraction of chemical short range order parameters from the x-ray PDF of a quenched Cu3Au sample.
S D Conradson - One of the best experts on this subject based on the ideXlab platform.
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Pair Distribution function and structure factor of spherical particles
Physical Review B, 2006Co-Authors: Rafael C Howell, Thomas Proffen, S D ConradsonAbstract:The availability of neutron spallation-source instruments that provide total scattering powder diffraction has led to an increased application of real-space structure analysis using the Pair Distribution function. Currently, the analytical treatment of finite size effects within Pair Distribution refinement procedures is limited. To that end, an envelope function is derived which transforms the Pair Distribution function of an infinite solid into that of a spherical particle with the same crystal structure. Distributions of particle sizes are then considered, and the associated envelope function is used to predict the particle size Distribution of an experimental sample of gold nanoparticles from its Pair Distribution function alone. Finally, complementing the wealth of existing diffraction analysis, the peak broadening for the structure factor of spherical particles, expressed as a convolution derived from the envelope functions, is calculated exactly for all particle size Distributions considered, and peak maxima, offsets, and asymmetries are discussed.
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Pair Distribution function and structure factor of spherical particles
Physical Review B, 2006Co-Authors: Rafael C Howell, Thomas Proffen, S D ConradsonAbstract:The availability of neutron spallation-source instruments that provide total scattering powder diffraction has led to an increased application of real-space structure analysis using the Pair Distribution function. Currently, the analytical treatment of finite size effects within Pair Distribution refinement procedures is limited. To that end, an envelope function is derived which transforms the Pair Distribution function of an infinite solid into that of a spherical particle with the same crystal structure. Distributions of particle sizes are then considered, and the associated envelope function is used to predict the particle size Distribution of an experimental sample of gold nanoparticles from its Pair Distribution function alone. Finally, complementing the wealth of existing diffraction analysis, the peak broadening for the structure factor of spherical particles, expressed as a convolution derived from the envelope functions, is calculated exactly for all particle size Distributions considered, and peak maxima, offsets, and asymmetries are discussed.Comment: 7 pages, 6 figure
R.e. Davis - One of the best experts on this subject based on the ideXlab platform.
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Electromagnetic scattering calculated from Pair Distribution functions retrieved from planar snow sections
IEEE Transactions on Geoscience and Remote Sensing, 1997Co-Authors: Lisa M. Zurk, Leung Tsang, Jiancheng Shi, R.e. DavisAbstract:Electromagnetic wave scattering in dense media, such as snow, depends on the three-dimensional (3D) Pair Distribution function of particle positions. In snow, two-dimensional (2D) stereological data can be obtained by analyzing planar sections. In this paper the authors calculate the volume 3D Pair Distribution functions from the 2D stereological data by solving Hanisch's integral equation. They first use Monte Carlo simulations for multisize particles to verify the procedure. Next they apply the procedure to available planar snow sections. A log-normal Distribution of particle sizes is assumed for the ice grains in snow. To derive multisize Pair functions, a least squares fit is used to recover Pair functions for particles with sufficient number density and the hole correction approximation is assumed for the larger particles. A family of 3D Pair Distribution functions are derived. These are then substituted into dense media scattering theory to calculate scattering. It is found that the computed scattering rates are comparable to those calculated under the Percus-Yevick approximation of Pair Distribution functions of multiple sizes.
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Electromagnetic scattering based on Pair Distribution functions retrieved from planar snow sections
IGARSS '96. 1996 International Geoscience and Remote Sensing Symposium, 1Co-Authors: Lisa M. Zurk, Leung Tsang, Jiancheng Shi, R.e. DavisAbstract:Electromagnetic wave propagation and scattering in dense media depends on the 3D Pair Distribution function of particle positions. In the past researchers have assumed a form, such as Percus-Yevick (PY), for the Pair function in snow. Recent efforts in the snow community have concentrated on analyzing planar snow sections to obtain 2D stereological data. In this paper the authors calculate the volume 3D Pair Distribution function from the 2D stereological data by solving Hanisch's integral equation (1983). They first use Monte Carlo simulations for single and multi-size particles to verify the inversion procedure with good results. Next they apply the procedure to available planar snow sections. A log-normal Distribution of particle sizes is assumed for the ice grains in snow with the Distribution parameters derived from stereological measurements. The 3D Pair function can be expressed as a weighted sum of size specific Pair functions which are necessary for scattering calculations. They choose a small number of representative particle sizes and use a least squares non-linear fit to decompose the 3D Pair function into Pair functions for those particles. The fit procedure is constrained by a set of physically meaningful rules and can only be applied to those sizes with sufficient number densities. Analysis of scattering from log-normally distributed spheres indicates the larger particles contribute strongly to the independent scattering but have relatively small interaction terms. Since the large, sparsely distributed particles are not retrievable from the fit and have relatively small interaction terms the authors include their scattering contribution by using the hole correction approximation. The family of recovered Pair Distribution functions gives scattering rates comparable to those calculated under the PY approximation.
Peter J. Chupas - One of the best experts on this subject based on the ideXlab platform.
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Pair Distribution function analysis of pressure treated zeolite Na-A
Chemical communications (Cambridge England), 2009Co-Authors: Jennifer E. Readman, Paul M. Forster, Karena W. Chapman, Peter J. Chupas, John B. Parise, Joseph A. HriljacAbstract:Pair Distribution function studies using X-ray scattering data from zeolite Na-A samples treated at pressure up to 8 GPa indicate a pressure-induced amorphisation mechanism involving loss of crystallographic order of the aluminosilicate framework but retention of the local sodium to oxygen bonding.
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Quantitative high-pressure Pair Distribution function analysis.
Journal of synchrotron radiation, 2005Co-Authors: John B. Parise, Peter J. Chupas, Sytle M Antao, F Marc Michel, C David Martin, Sarvjit D Shastri, Peter L LeeAbstract:The collection of scattering data at high pressure and temperature is now relatively straightforward thanks to developments at high-brightness synchrotron radiation facilities. Reliable data from powders, that are suitable for structure determination and Rietveld refinement, are routinely collected up to about 30 GPa in either a large-volume high-pressure apparatus or diamond anvil cell. In those cases where the total elastic scattering is of interest, as it is in the case of nano-crystalline and glassy materials, technical developments, including the use of focused high-energy X-rays (>80 keV), are advantageous. Recently completed experiments on nano-crystalline materials at the 1-ID beamline at the Advanced Photon Source suggest that quantitative data, suitable for Pair Distribution function analysis, can be obtained.
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rapid acquisition Pair Distribution function ra pdf analysis
Journal of Applied Crystallography, 2003Co-Authors: Peter J. Chupas, Peter L Lee, Xiangyun Qiu, Jonathan C Hanson, Clare P Grey, Simon J L BillingeAbstract:An image-plate (IP) detector coupled with high-energy synchrotron radiation was used for atomic Pair Distribution function (PDF) analysis, with high probed momentum transfer Qmax ≤ 28.5 A−1, from crystalline materials. Materials with different structural complexities were measured to test the validity of the quantitative data analysis. Experimental results are presented for crystalline Ni, crystalline α-AlF3, and the layered Aurivillius type oxides α-Bi4V2O11 and γ-Bi4V1.7Ti0.3O10.85. Overall, the diffraction patterns show good counting statistics, with measuring time from one to tens of seconds. The PDFs obtained are of high quality. Structures may be refined from these PDFs, and the structural models are consistent with the published literature. Data sets from similar samples are highly reproducible.
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rapid acquisition Pair Distribution function ra pdf analysis
arXiv: Condensed Matter, 2003Co-Authors: Peter J. Chupas, Peter L Lee, Xiangyun Qiu, Jonathan C Hanson, Clare P Grey, Simon J L BillingeAbstract:An image plate (IP) detector coupled with high energy synchrotron radiation was used for atomic Pair Distribution function (PDF) analysis, with high probed momentum transfer \Qmax $\leq 28.5$ \RAA from crystalline materials. Materials with different structural complexities were measured to test the validity of the quantitative data analysis. Experimental results are presented here for crystalline Ni, crystalline \alf, and the layered Aurivillius type oxides \bivo and \bivtio . Overall, the diffraction patterns show good counting statistics with measuring time from one to tens of seconds. The PDFs obtained are of high quality. Structures may be refined from these PDFs, and the structural models are consistent with the published literature. Data sets from similar samples are highly reproducible.
