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Claude Pouchan - One of the best experts on this subject based on the ideXlab platform.
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Electrostatic interaction schemes for evaluating the Polarizability of silicon clusters
Journal of Chemical Physics, 2009Co-Authors: Marion Guillaume, B. Champagne, Didier Bégué, Claude PouchanAbstract:Electrostatic interaction schemes have been applied to predict the evolution of the Polarizability in Sin clusters of increasing size (n=3-19). Both on-site polarization and charge transfer effects have been included in the interaction scheme, of which the values have been compared to B3LYP/6-311 G* and other first principles results. To reproduce the pattern of the variation of the B3LYP average Polarizability per Si atom as a function of the cluster size, the atomic Polarizability employed in the interaction scheme should amount to roughly 80% of the bulk atomic Polarizability. However, this results in a systematic underestimation of the Polarizability per Si atom by about 25%, whereas increasing the atomic Polarizability value leads to excessive variations of the Polarizability per Si with the cluster size. An improved agreement is obtained when incorporating a charge transfer contribution, at least for sufficiently large clusters, substantiating the fact that in large clusters electrostatic effects are dominant over quantum effects. This charge transfer atomic Polarizability term has been modeled by a simple function, which evolves linearly with the difference of Cartesian coordinates between the atom and the center of mass and that has been verified using B3LYP/6-311 G* calculations. In the case of the prediction of the Polarizability anisotropy, a similar atomic Polarizability corresponding to 80% of the bulk atomic Polarizability has been shown suitable to reproduce the B3LYP results, whereas inclusion of charge transfer effects can slightly improve the agreement, provided the amount of charge transfer increases with the size of the cluster. © 2009 American Institute of Physics.
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Structure, stability, dipole Polarizability and differential Polarizability in small gallium arsenide clusters from all-electron ab initio and density-functional-theory calculations
Physical Review A - Atomic Molecular and Optical Physics, 2008Co-Authors: Panaghiotis Karamanis, Claude Pouchan, G. MaroulisAbstract:We have employed conventional ab initio and density-functional-theory (DFT) methods to study the structure, stability and electric Polarizability of small gallium arsenide clusters Gan Asn. We relied on purpose-oriented, carefully optimized basis sets of Gaussian-type functions. We have calculated both the mean dipole Polarizability (ᾱ) and the anisotropy (Δα). Our results show that the differential-per-atom Polarizability of the most stable isomers decreases rapidly with cluster size. Compared to the ab initio results, the widely used Becke's three-parameter exchange DFT functional with the Lee, Yang, and Parr correlation functional and Becke's three-parameter exchange DFT functional with Perdew and Wang's 1991 gradient-corrected correlation functional density-functional-theory methods follow clearly the trend of the differential-per-atom Polarizability ᾱ diff atom for the most stable isomers and predict values closer to the self-consistent field method but distinctly lower than second-order Møller-Plesset perturbation theory. All methods predict a positive value for the dimer, ᾱ diff atom (Ga2 As2) >0. © 2008 The American Physical Society.
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Between geometry, stability, and Polarizability: Density functional theory studies of silicon clusters Si n(n=3-10)
Journal of Chemical Physics, 2004Co-Authors: Claude Pouchan, Didier Bégué, D.y. ZhangAbstract:The use of density functional theory (DFT) method to analyze the Polarizability, stability and geometry of silicon clusters was discussed. Investigations show that the Polarizability per atom was directly related to the energy gap between the bonding and antibonding orbitals. The degree of prolate structure results in a smaller highest occupied molecular orbitals-lowest unoccupied molecular orbital (HOMO-LUMO) gap, which was reflected in the larger Polarizability. The results show that the straightforward correlations provided a means to predict the physical properties, Polarizability and the stability based on the structural information of cluster.
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Density functional theory studies of correlations between structure, binding energy, and dipole Polarizability in Si9 Si12
Chemical Physics Letters, 2004Co-Authors: D.y. Zhang, Didier Bégué, Claude PouchanAbstract:Two medium-size silicon clusters, namely, Si9 and Si12, have been used as model systems to investigate the correlations between structure, stability, and the static dipole Polarizability by theoretical methods. Results show that Polarizability correlates with the standard deviation of the atomic distances, and that the binding energy correlates with both the averaged atomic distance and the number of Si-Si bonds formed in the particular cluster. These correlations are significant, since they allow predictions of certain physical properties, i.e., dipole Polarizability and stability, based solely on the structural information of the cluster. © 2004 Elsevier B.V. All rights reserved.
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Dynamic Polarizability and hyperPolarizability for the 14 electron molecules CO and BF
Chemical Physics Letters, 1997Co-Authors: M. MÉrawa, Didier Bégué, M. Rérat, Claude PouchanAbstract:The dynamic Polarizability and hyperPolarizability for the 14 electron diatomics CO and BF have been obtained from a time-dependent gauge invariant (TDGI) method. The results compare well with both experimental and theoretical calculations for CO. The frequency-dependent dipole Polarizability and hyperPolarizability presented here are new for BF. In all cases the dynamic components are calculated for the dipole Polarizability and electro-optic Pockels effect for the three first resonances.
Didier Bégué - One of the best experts on this subject based on the ideXlab platform.
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Electrostatic interaction schemes for evaluating the Polarizability of silicon clusters
Journal of Chemical Physics, 2009Co-Authors: Marion Guillaume, B. Champagne, Didier Bégué, Claude PouchanAbstract:Electrostatic interaction schemes have been applied to predict the evolution of the Polarizability in Sin clusters of increasing size (n=3-19). Both on-site polarization and charge transfer effects have been included in the interaction scheme, of which the values have been compared to B3LYP/6-311 G* and other first principles results. To reproduce the pattern of the variation of the B3LYP average Polarizability per Si atom as a function of the cluster size, the atomic Polarizability employed in the interaction scheme should amount to roughly 80% of the bulk atomic Polarizability. However, this results in a systematic underestimation of the Polarizability per Si atom by about 25%, whereas increasing the atomic Polarizability value leads to excessive variations of the Polarizability per Si with the cluster size. An improved agreement is obtained when incorporating a charge transfer contribution, at least for sufficiently large clusters, substantiating the fact that in large clusters electrostatic effects are dominant over quantum effects. This charge transfer atomic Polarizability term has been modeled by a simple function, which evolves linearly with the difference of Cartesian coordinates between the atom and the center of mass and that has been verified using B3LYP/6-311 G* calculations. In the case of the prediction of the Polarizability anisotropy, a similar atomic Polarizability corresponding to 80% of the bulk atomic Polarizability has been shown suitable to reproduce the B3LYP results, whereas inclusion of charge transfer effects can slightly improve the agreement, provided the amount of charge transfer increases with the size of the cluster. © 2009 American Institute of Physics.
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Between geometry, stability, and Polarizability: Density functional theory studies of silicon clusters Si n(n=3-10)
Journal of Chemical Physics, 2004Co-Authors: Claude Pouchan, Didier Bégué, D.y. ZhangAbstract:The use of density functional theory (DFT) method to analyze the Polarizability, stability and geometry of silicon clusters was discussed. Investigations show that the Polarizability per atom was directly related to the energy gap between the bonding and antibonding orbitals. The degree of prolate structure results in a smaller highest occupied molecular orbitals-lowest unoccupied molecular orbital (HOMO-LUMO) gap, which was reflected in the larger Polarizability. The results show that the straightforward correlations provided a means to predict the physical properties, Polarizability and the stability based on the structural information of cluster.
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Density functional theory studies of correlations between structure, binding energy, and dipole Polarizability in Si9 Si12
Chemical Physics Letters, 2004Co-Authors: D.y. Zhang, Didier Bégué, Claude PouchanAbstract:Two medium-size silicon clusters, namely, Si9 and Si12, have been used as model systems to investigate the correlations between structure, stability, and the static dipole Polarizability by theoretical methods. Results show that Polarizability correlates with the standard deviation of the atomic distances, and that the binding energy correlates with both the averaged atomic distance and the number of Si-Si bonds formed in the particular cluster. These correlations are significant, since they allow predictions of certain physical properties, i.e., dipole Polarizability and stability, based solely on the structural information of the cluster. © 2004 Elsevier B.V. All rights reserved.
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Dynamic Polarizability and hyperPolarizability for the 14 electron molecules CO and BF
Chemical Physics Letters, 1997Co-Authors: M. MÉrawa, Didier Bégué, M. Rérat, Claude PouchanAbstract:The dynamic Polarizability and hyperPolarizability for the 14 electron diatomics CO and BF have been obtained from a time-dependent gauge invariant (TDGI) method. The results compare well with both experimental and theoretical calculations for CO. The frequency-dependent dipole Polarizability and hyperPolarizability presented here are new for BF. In all cases the dynamic components are calculated for the dipole Polarizability and electro-optic Pockels effect for the three first resonances.
D.y. Zhang - One of the best experts on this subject based on the ideXlab platform.
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Between geometry, stability, and Polarizability: Density functional theory studies of silicon clusters Si n(n=3-10)
Journal of Chemical Physics, 2004Co-Authors: Claude Pouchan, Didier Bégué, D.y. ZhangAbstract:The use of density functional theory (DFT) method to analyze the Polarizability, stability and geometry of silicon clusters was discussed. Investigations show that the Polarizability per atom was directly related to the energy gap between the bonding and antibonding orbitals. The degree of prolate structure results in a smaller highest occupied molecular orbitals-lowest unoccupied molecular orbital (HOMO-LUMO) gap, which was reflected in the larger Polarizability. The results show that the straightforward correlations provided a means to predict the physical properties, Polarizability and the stability based on the structural information of cluster.
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Density functional theory studies of correlations between structure, binding energy, and dipole Polarizability in Si9 Si12
Chemical Physics Letters, 2004Co-Authors: D.y. Zhang, Didier Bégué, Claude PouchanAbstract:Two medium-size silicon clusters, namely, Si9 and Si12, have been used as model systems to investigate the correlations between structure, stability, and the static dipole Polarizability by theoretical methods. Results show that Polarizability correlates with the standard deviation of the atomic distances, and that the binding energy correlates with both the averaged atomic distance and the number of Si-Si bonds formed in the particular cluster. These correlations are significant, since they allow predictions of certain physical properties, i.e., dipole Polarizability and stability, based solely on the structural information of the cluster. © 2004 Elsevier B.V. All rights reserved.
Alex Becker - One of the best experts on this subject based on the ideXlab platform.
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Resolution depths for some transmitter-receiver configurations
IEEE Transactions on Geoscience and Remote Sensing, 2004Co-Authors: J.t. Smith, H. F. Morrison, Alex BeckerAbstract:Equivalent dipole Polarizability matrices and equivalent dipole location are a convenient way to interpret magnetic field data due to currents induced in isolated conductive objects. The uncertainties in Polarizability estimates and in the equivalent dipole location provide a quantitative measure of the performance of different configurations of transmitters and receivers. In another paper, we estimate these uncertainties using a linearized inversion. For many systems, consisting of one or more rectangular loop transmitters and a number of dipole receivers, sited on a horizontal grid, equivalent dipole depth is determined to 10% accuracy to depths approximately 20% deeper than the depths at which Polarizability matrix elements can be determined to the same precision. Systems that have a lower product of rms Polarizability uncertainty and square root of their number of transmitter-receiver pairs are considered more effective for the number of transmitter-receiver pairs. Among the systems studied, a system with three orthogonal transmitter loops and a three-component receiver is the most effective, for objects shallower than 0.6 times the instrument siting grid spacing, yielding an rms Polarizability uncertainty 0.04 times that of a single-transmitter single-receiver system. At intermediate depths, a system with two vertical component receivers on the diagonal of a square horizontal transmitter loop is most effective for its number of transmitter-receiver pairs, yielding an rms Polarizability uncertainty 0.07 times that of a single receiver system. At depths greater than 2.5 times, the siting grid spacing a three-orthogonal loop transmitter with a single vertical component receiver is about the most effective for its number of transmitter-receiver pairs, yielding an rms Polarizability uncertainty 0.08 times that of a single-transmitter system.
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Depths of equivalent dipole Polarizability resolution for some transmitter receiver configurations
Lawrence Berkeley National Laboratory, 2002Co-Authors: J.t. Smith, H. F. Morrison, Alex BeckerAbstract:Equivalent dipole Polarizability matrices and equivalent dipole location are a convenient way to summarize magnetic induction data arising from currents induced in isolated conductive objects. The uncertainties in Polarizability estimates and in equivalent dipole location provide a quantitative measure of the performance of different configurations of transmitters and receivers. Uncertainties in equivalent dipole Polarizability matrices and equivalent dipole position are estimated using a linearized inversion. For a number of systems of rectangular loop transmitters and dipole receivers sited on a horizontal grid, equivalent dipole depth is determined to 10% approximately 20% deeper, than the Polarizability matrix elements can be determined to the same precision. Systems that have a lower product of rms Polarizability uncertainty and square root of their number of transmitter-receiver pairs are considered more effective for their number of transmitter-receiver pairs. Among the systems studied, a system with three orthogonal transmitter loops and a three component receiver is the most effective, for objects shallower than 0.6 times the instrument siting grid spacing, yielding an rms Polarizability uncertainty 0.04 times that of a single transmitter single receiver system. At intermediate depths, a system with two vertical component receivers on the diagonal of a horizontal transmitter loop is most effectivemore » for its number of transmitter-receiver pairs, yielding an rms Polarizability uncertainty 0.07 times that of a single receiver system. At depths greater than 2.5 times the siting grid spacing a 3 orthogonal loop transmitter with a single vertical component receiver is about the most effective for its number of transmitter-receiver pairs, yielding an rms Polarizability uncertainty 0.08 times that of a single transmitter system.« less
J.t. Smith - One of the best experts on this subject based on the ideXlab platform.
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Resolution depths for some transmitter-receiver configurations
IEEE Transactions on Geoscience and Remote Sensing, 2004Co-Authors: J.t. Smith, H. F. Morrison, Alex BeckerAbstract:Equivalent dipole Polarizability matrices and equivalent dipole location are a convenient way to interpret magnetic field data due to currents induced in isolated conductive objects. The uncertainties in Polarizability estimates and in the equivalent dipole location provide a quantitative measure of the performance of different configurations of transmitters and receivers. In another paper, we estimate these uncertainties using a linearized inversion. For many systems, consisting of one or more rectangular loop transmitters and a number of dipole receivers, sited on a horizontal grid, equivalent dipole depth is determined to 10% accuracy to depths approximately 20% deeper than the depths at which Polarizability matrix elements can be determined to the same precision. Systems that have a lower product of rms Polarizability uncertainty and square root of their number of transmitter-receiver pairs are considered more effective for the number of transmitter-receiver pairs. Among the systems studied, a system with three orthogonal transmitter loops and a three-component receiver is the most effective, for objects shallower than 0.6 times the instrument siting grid spacing, yielding an rms Polarizability uncertainty 0.04 times that of a single-transmitter single-receiver system. At intermediate depths, a system with two vertical component receivers on the diagonal of a square horizontal transmitter loop is most effective for its number of transmitter-receiver pairs, yielding an rms Polarizability uncertainty 0.07 times that of a single receiver system. At depths greater than 2.5 times, the siting grid spacing a three-orthogonal loop transmitter with a single vertical component receiver is about the most effective for its number of transmitter-receiver pairs, yielding an rms Polarizability uncertainty 0.08 times that of a single-transmitter system.
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Depths of equivalent dipole Polarizability resolution for some transmitter receiver configurations
Lawrence Berkeley National Laboratory, 2002Co-Authors: J.t. Smith, H. F. Morrison, Alex BeckerAbstract:Equivalent dipole Polarizability matrices and equivalent dipole location are a convenient way to summarize magnetic induction data arising from currents induced in isolated conductive objects. The uncertainties in Polarizability estimates and in equivalent dipole location provide a quantitative measure of the performance of different configurations of transmitters and receivers. Uncertainties in equivalent dipole Polarizability matrices and equivalent dipole position are estimated using a linearized inversion. For a number of systems of rectangular loop transmitters and dipole receivers sited on a horizontal grid, equivalent dipole depth is determined to 10% approximately 20% deeper, than the Polarizability matrix elements can be determined to the same precision. Systems that have a lower product of rms Polarizability uncertainty and square root of their number of transmitter-receiver pairs are considered more effective for their number of transmitter-receiver pairs. Among the systems studied, a system with three orthogonal transmitter loops and a three component receiver is the most effective, for objects shallower than 0.6 times the instrument siting grid spacing, yielding an rms Polarizability uncertainty 0.04 times that of a single transmitter single receiver system. At intermediate depths, a system with two vertical component receivers on the diagonal of a horizontal transmitter loop is most effectivemore » for its number of transmitter-receiver pairs, yielding an rms Polarizability uncertainty 0.07 times that of a single receiver system. At depths greater than 2.5 times the siting grid spacing a 3 orthogonal loop transmitter with a single vertical component receiver is about the most effective for its number of transmitter-receiver pairs, yielding an rms Polarizability uncertainty 0.08 times that of a single transmitter system.« less
