The Experts below are selected from a list of 213 Experts worldwide ranked by ideXlab platform
Yasuteru Shigeta - One of the best experts on this subject based on the ideXlab platform.
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Distribution Function in quantal cumulant dynamics
The Journal of chemical physics, 2008Co-Authors: Yasuteru ShigetaAbstract:We have derived a quantum Distribution Function in terms of cumulants that are expectation values of a (anti)symmetric-ordered product of position and momentum fluctuation operators. A second-order approximation leads a Gaussian Distribution Function, which is positive definite and has proper marginals so that the Shannon entropy can be evaluated.
Simon J L Billinge - One of the best experts on this subject based on the ideXlab platform.
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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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Density fluctuations and the pair Distribution Function
Physical Review B, 2005Co-Authors: Valentin A. Levashov, Simon J L Billinge, Michael ThorpeAbstract:In discrete systems the number density, defined as the number of particles per unit volume, is subject to fluctuations depending on the size and location of the sampling volume. Fluctuations in the local density or pair Distribution Function as determined from x-ray or neutron diffraction experiments, die out quickly in disordered materials but persist in crystals. Here we show that for a single atom at the origin, fluctuations persist out to very large distances and the pair Distribution Function does not decay, even in the case of a random system; only disappearing after ensemble averaging. Therefore, for a crystal the fluctuations in the pair Distribution Function persist to arbitrarily large distances. This is demonstrated here with experimental and modeling results for powdered crystalline nickel, where we find an undiminished fluctuation amplitude for the pair Distribution Function calculated up to distances of a micron. The characteristic separation between the peaks in the pair Distribution Function at large distances is determined by the thermal amplitude of vibration of a single atom and not by the interatomic spacing. Thermal broadening is included so the results obtained here are of direct experimental interest, and comparison is made to neutron diffraction data on nickel. Resultsmore » are shown to be similar for crystals and for a single atom in a glass.« less
Michael Thorpe - One of the best experts on this subject based on the ideXlab platform.
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Density fluctuations and the pair Distribution Function
Physical Review B, 2005Co-Authors: Valentin A. Levashov, Simon J L Billinge, Michael ThorpeAbstract:In discrete systems the number density, defined as the number of particles per unit volume, is subject to fluctuations depending on the size and location of the sampling volume. Fluctuations in the local density or pair Distribution Function as determined from x-ray or neutron diffraction experiments, die out quickly in disordered materials but persist in crystals. Here we show that for a single atom at the origin, fluctuations persist out to very large distances and the pair Distribution Function does not decay, even in the case of a random system; only disappearing after ensemble averaging. Therefore, for a crystal the fluctuations in the pair Distribution Function persist to arbitrarily large distances. This is demonstrated here with experimental and modeling results for powdered crystalline nickel, where we find an undiminished fluctuation amplitude for the pair Distribution Function calculated up to distances of a micron. The characteristic separation between the peaks in the pair Distribution Function at large distances is determined by the thermal amplitude of vibration of a single atom and not by the interatomic spacing. Thermal broadening is included so the results obtained here are of direct experimental interest, and comparison is made to neutron diffraction data on nickel. Resultsmore » are shown to be similar for crystals and for a single atom in a glass.« less
Andrew M Beale - One of the best experts on this subject based on the ideXlab platform.
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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.
Simon D M Jacques - One of the best experts on this subject based on the ideXlab platform.
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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.
