The Experts below are selected from a list of 65058 Experts worldwide ranked by ideXlab platform
Joost Vandevondele - One of the best experts on this subject based on the ideXlab platform.
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electron correlation in the condensed phase from a resolution of identity approach based on the gaussian and Plane Waves scheme
Journal of Chemical Theory and Computation, 2013Co-Authors: Jurg Hutter, Joost VandevondeleAbstract:The second-order Moller–Plesset perturbation energy (MP2) and the Random Phase Approximation (RPA) correlation energy are increasingly popular post-Kohn–Sham correlation methods. Here, a novel algorithm based on a hybrid Gaussian and Plane Waves (GPW) approach with the resolution-of-identity (RI) approximation is developed for MP2, scaled opposite-spin MP2 (SOS-MP2), and direct-RPA (dRPA) correlation energies of finite and extended system. The key feature of the method is that the three center electron repulsion integrals (μν|P) necessary for the RI approximation are computed by direct integration between the products of Gaussian basis functions μν and the electrostatic potential arising from the RI fitting densities P. The electrostatic potential is obtained in a Plane Waves basis set after solving the Poisson equation in Fourier space. This scheme is highly efficient for condensed phase systems and offers a particularly easy way for parallel implementation. The RI approximation allows to speed up the MP...
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second order moller plesset perturbation theory in the condensed phase an efficient and massively parallel gaussian and Plane Waves approach
Journal of Chemical Theory and Computation, 2012Co-Authors: Juerg Hutter, Joost VandevondeleAbstract:A novel algorithm, based on a hybrid Gaussian and Plane Waves (GPW) approach, is developed for the canonical second-order Moller–Plesset perturbation energy (MP2) of finite and extended systems. The key aspect of the method is that the electron repulsion integrals (ia|λσ) are computed by direct integration between the products of Gaussian basis functions λσ and the electrostatic potential arising from a given occupied-virtual pair density ia. The electrostatic potential is obtained in a Plane Waves basis set after solving the Poisson equation in Fourier space. In particular, for condensed phase systems, this scheme is highly efficient. Furthermore, our implementation has low memory requirements and displays excellent parallel scalability up to 100 000 processes. In this way, canonical MP2 calculations for condensed phase systems containing hundreds of atoms or more than 5000 basis functions can be performed within minutes, while systems up to 1000 atoms and 10 000 basis functions remain feasible. Solid Li...
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second order moller plesset perturbation theory in the condensed phase an efficient and massively parallel gaussian and Plane Waves approach
Journal of Chemical Theory and Computation, 2012Co-Authors: Mauro Del Ben, Juerg Hutter, Joost VandevondeleAbstract:A novel algorithm, based on a hybrid Gaussian and Plane Waves (GPW) approach, is developed for the canonical second-order Moller-Plesset perturbation energy (MP2) of finite and extended systems. The key aspect of the method is that the electron repulsion integrals (ia|λσ) are computed by direct integration between the products of Gaussian basis functions λσ and the electrostatic potential arising from a given occupied-virtual pair density ia. The electrostatic potential is obtained in a Plane Waves basis set after solving the Poisson equation in Fourier space. In particular, for condensed phase systems, this scheme is highly efficient. Furthermore, our implementation has low memory requirements and displays excellent parallel scalability up to 100 000 processes. In this way, canonical MP2 calculations for condensed phase systems containing hundreds of atoms or more than 5000 basis functions can be performed within minutes, while systems up to 1000 atoms and 10 000 basis functions remain feasible. Solid LiH has been employed as a benchmark to study basis set and system size convergence. Lattice constants and cohesive energies of various molecular crystals have been studied with MP2 and double-hybrid functionals.
Tom G. Mackay - One of the best experts on this subject based on the ideXlab platform.
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Plane Waves with negative phase velocity in isotropic chiral mediums
Microwave and Optical Technology Letters, 2005Co-Authors: Tom G. MackayAbstract:The propagation of Plane Waves in an isotropic chiral medium (ICM) is investigated. Simple conditions are derived—in terms of the constitutive parameters of the ICM—for the phase velocity to be directed opposite to the direction of power flow. It is demonstrated that phase velocity and power flow may be oppositely directed, provided that the magneto-electric coupling is sufficiently strong. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 120–121, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20742
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Plane Waves with negative phase velocity in isotropic chiral mediums
arXiv: Optics, 2004Co-Authors: Tom G. MackayAbstract:The propagation of Plane Waves in an isotropic chiral medium (ICM) is investigated. Simple conditions are derived--in terms of the constitutive parameters of the ICM--for the phase velocity to be directed opposite to the direction of power flow. It is demonstrated that phase velocity and power flow may be oppositely directed provided that the magnetoelectric coupling is sufficiently strong.
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Plane Waves with negative phase velocity in Faraday chiral mediums.
Physical review. E Statistical nonlinear and soft matter physics, 2004Co-Authors: Tom G. Mackay, Akhlesh LakhtakiaAbstract:The propagation of Plane Waves in a Faraday chiral medium is investigated. Conditions for the phase velocity to be directed opposite to the direction of power flow are derived for propagation in an arbitrary direction; simplified conditions which apply to propagation parallel to the distinguished axis are also established. These negative phase-velocity conditions are explored numerically using a representative Faraday chiral medium, arising from the homogenization of an isotropic chiral medium and a magnetically biased ferrite. It is demonstrated that the phase velocity may be directed opposite to power flow, provided that the gyrotropic parameter of the ferrite component medium is sufficiently large compared with the corresponding nongyrotropic permeability parameters.
Akhlesh Lakhtakia - One of the best experts on this subject based on the ideXlab platform.
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Plane Waves with negative phase velocity in Faraday chiral mediums.
Physical review. E Statistical nonlinear and soft matter physics, 2004Co-Authors: Tom G. Mackay, Akhlesh LakhtakiaAbstract:The propagation of Plane Waves in a Faraday chiral medium is investigated. Conditions for the phase velocity to be directed opposite to the direction of power flow are derived for propagation in an arbitrary direction; simplified conditions which apply to propagation parallel to the distinguished axis are also established. These negative phase-velocity conditions are explored numerically using a representative Faraday chiral medium, arising from the homogenization of an isotropic chiral medium and a magnetically biased ferrite. It is demonstrated that the phase velocity may be directed opposite to power flow, provided that the gyrotropic parameter of the ferrite component medium is sufficiently large compared with the corresponding nongyrotropic permeability parameters.
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Spectral responses of gyrotropic chiral sculptured thin films to obliquely incident Plane Waves
Optik, 2004Co-Authors: Matthew D. Pickett, Akhlesh Lakhtakia, John A. PoloAbstract:Summary Gyrotropic chiral sculptured thin films (STFs) exhibit optical activity due to their structural chirality, local anisotropy, and magneto-optic gyrotropy. We adapted two algorithms for nongyrotopic chiral STFs to investigate the circular-polarization-sensitivity of gyrotropic chiral STFs to incident Plane Waves. The impacts of gyrotropy and oblique angles of incidence on the reflectances and the transmittances were examined, and several conclusions drawn. In particular, we found that the incorporation of gyrotropy results in a blueshift of the Bragg regime.
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does the photon have an elementary magnetostatic flux density i Plane Waves
Physica B-condensed Matter, 1993Co-Authors: Akhlesh LakhtakiaAbstract:Abstract It has been claimed that a magnetostatic field B Π is a fundamental property of circularly polarized Plane Waves. It is shown here that this magnetostatic field can hardly be considered to be fundamental, and it can be defined for any elliptically polarized Plane wave.
Juerg Hutter - One of the best experts on this subject based on the ideXlab platform.
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second order moller plesset perturbation theory in the condensed phase an efficient and massively parallel gaussian and Plane Waves approach
Journal of Chemical Theory and Computation, 2012Co-Authors: Juerg Hutter, Joost VandevondeleAbstract:A novel algorithm, based on a hybrid Gaussian and Plane Waves (GPW) approach, is developed for the canonical second-order Moller–Plesset perturbation energy (MP2) of finite and extended systems. The key aspect of the method is that the electron repulsion integrals (ia|λσ) are computed by direct integration between the products of Gaussian basis functions λσ and the electrostatic potential arising from a given occupied-virtual pair density ia. The electrostatic potential is obtained in a Plane Waves basis set after solving the Poisson equation in Fourier space. In particular, for condensed phase systems, this scheme is highly efficient. Furthermore, our implementation has low memory requirements and displays excellent parallel scalability up to 100 000 processes. In this way, canonical MP2 calculations for condensed phase systems containing hundreds of atoms or more than 5000 basis functions can be performed within minutes, while systems up to 1000 atoms and 10 000 basis functions remain feasible. Solid Li...
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second order moller plesset perturbation theory in the condensed phase an efficient and massively parallel gaussian and Plane Waves approach
Journal of Chemical Theory and Computation, 2012Co-Authors: Mauro Del Ben, Juerg Hutter, Joost VandevondeleAbstract:A novel algorithm, based on a hybrid Gaussian and Plane Waves (GPW) approach, is developed for the canonical second-order Moller-Plesset perturbation energy (MP2) of finite and extended systems. The key aspect of the method is that the electron repulsion integrals (ia|λσ) are computed by direct integration between the products of Gaussian basis functions λσ and the electrostatic potential arising from a given occupied-virtual pair density ia. The electrostatic potential is obtained in a Plane Waves basis set after solving the Poisson equation in Fourier space. In particular, for condensed phase systems, this scheme is highly efficient. Furthermore, our implementation has low memory requirements and displays excellent parallel scalability up to 100 000 processes. In this way, canonical MP2 calculations for condensed phase systems containing hundreds of atoms or more than 5000 basis functions can be performed within minutes, while systems up to 1000 atoms and 10 000 basis functions remain feasible. Solid LiH has been employed as a benchmark to study basis set and system size convergence. Lattice constants and cohesive energies of various molecular crystals have been studied with MP2 and double-hybrid functionals.
Mohamed I A Othman - One of the best experts on this subject based on the ideXlab platform.
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Plane Waves in generalized thermo microstretch elastic solid with thermal relaxation using finite element method
International Journal of Thermophysics, 2012Co-Authors: Ibrahim A Abbas, Mohamed I A OthmanAbstract:The propagation of Plane Waves in a thermo-microstretch elastic solid half-space as proposed by Lord–Shulman as well as the classical dynamical coupled theory are discussed. The problem has been solved numerically using a finite element method. Numerical results for the displacement components, force stresses, temperature, couple stresses, and microstress distribution are obtained. The variations of the considered variables through the horizontal distance are given and illustrated graphically. Comparisons are made with the results predicted by the theory of generalized thermoelasticity for different values of the relaxation time.
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effect of rotation on Plane Waves in generalized thermo elasticity with two relaxation times
International Journal of Solids and Structures, 2004Co-Authors: Mohamed I A OthmanAbstract:The model of generalized thermo-elastic Plane Waves under the effect of rotation is studied using the theory of thermo-elasticity recently proposed by Green and Lindsay. The normal mode analysis is used to obtain the exact expressions for the temperature distribution, the displacement component and thermal stress. The resulting formulation is applied to two different concrete problems. The first deals with a thick plate subjected to a time-dependent heat source on each face. The second concerns the case of a heated punch moving across the surface of a semi-infinite thermo-elastic half-space subject to appropriate boundary conditions. Numerical results are given and illustrated graphically for each problem. Comparisons are made with the results predicted by the coupled theory and with the theory of generalized thermo-elasticity with two relaxation times in the absence of rotation.
