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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Few body systems 3 (1987), S. 95-98 
    ISSN: 1432-5411
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Orthonormal orbitals systematically constructed from the electron density have recently been employed to obtain a closed expression for an approximate energy functional. A comprehensive test of the new functional is carried out in a numerical way by means of the use of a trial density function. The results and several trends for future research are given in order to obtain more accurate results.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-6079
    Keywords: 31.20.L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract By using an approximate analytical trial density and the consideration of a Thomas-Fermi-Dirac Weizsäcker energy density functional, total ground-state energies, its different components and the expectation values 〈r n 〉 withn=−1, 1 and 2 are calculated for several atoms in the Periodic Table. The results are compared with Hartree-Fock values.
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  • 3
    ISSN: 0894-3230
    Keywords: 1,2,5-thiadiazole ; 1,1-dioxide derivatives ; single-crystal x-ray diffraction ; ab initio MO calculations ; structure ; conformation ; reactivity ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Single-crystal x-ray diffraction studies are reported for 3,4-dimethyl (I), 3-methyl-4-phenyl (II) and 3,4-diphenyl (III) derivatives of 1,2,5-thiadiazole 1,1-dioxide. Ab initio MO calculations on the electronic structure, conformation and reactivity of I, II and III are also reported and compared with the x-ray results. The structural data are related to previous kinetic and electrochemical experimental results on these compounds. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 61.50.Cj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spherically averaged pseudopotential (SAPS) calculations have been done for Mg n clusters, withn up to 250 within the framework of density functional theory. The electronic structure is computed resorting to the Thomas-Fermi-Dirac-Weizsäcker (TFDW) approximation for the kinetic energy. The equilibrium geometries have been obtained by minimizing the total cluster energy with respect to the atomic positions using the steepest-descent method. The ground state geometries obtained in this way are formed by spherical atomic shells, the number of them increasing with cluster size, up to a number of four for the biggest sizes considered here. An analysis of the distribution of the interatomic distances shows that the more internal is the shell, the more contracted are the interatomic distances. This effect diminishes progressively with increasing cluster size. For the purpose of comparison, similar calculations have been done with Cs n clusters in the same size range, allowing us to reproduce previous results obtained using a more elaborated density functional technique (Kohn-Sham method). The inhomogeneous contraction of interatomic distances then appears as a general fact for simple metallic clusters and not only for alkaline ones.
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  • 5
    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
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  • 6
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The search for a density functional theory (DFT) free of one-electron orbitals needs the development of good kinetic energy functionals beyond the venerable Thomas-Fermi and gradient expansion functionals. With this goal in mind, we previously solved for several atoms and positive ions the Euler equation associated with the exchange and kinetic energy functionals of the nonlocal weighted density approximation (WDA). In this work, we improve the theory by enforcing the correct asymptotic behavior of the exchange potential following a prescription of Przybilsky and Borstel (PB). We have calculated electronic densities, density moments 〈rn〉 (n = -1,1,2) and the density at the nucleus ρ(0), as well as total and exchange energies and chemical potentials for neutral and charged atoms. All those quantities show a better agreement with Hartree-Fock results than those obtained using gradient-corrected Thomas-Fermi functionals. The radial densities, 4πr2(r), show two local maxima at positions close to those of the first two maxima of Hartree-Fock radial densities. This effect, which is absent in the self-consistent densities from the usual gradient-corrected Thomas-Fermi functions, can be interpreted, in our view as an incipient emergence of the shell effect. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nonlocal weighted density approximation (WDA) to the exchange and kinetic energy functionals of many-electron systems proposed several years ago by Alonso and Girifalco in the context of density functional theory is used to compute, within the framework of the spherical jellium model, the ground-state electronic density, chemical potential, and total energy of neutral and negatively and positively charged sodium clusters containing up to N = 800 atoms. From these calculations, we study the behavior of the total energies per atom, chemical potentials, ionization potentials, I(N), and electron affinities, A(N). These results are compared with analogous calculations using the well-known Thomas-Fermi-Weizsäcker-Dirac (TFWD) approximation for the kinetic (TFW) and exchange (D) energy functionals. Calculations including the local density approximation (LDA) to the correlation energy in both WDA and TFWD functionals are also presented. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nonlocal weighted density approximation (WDA) to the exchange and kinetic-energy functionals of many electron systems proposed several years ago by Alonso and Girifalco is used to compute, within the framework of density functional theory, the ground-state electronic density and total energy of noble gas atoms and of neutral jellium-like sodium clusters containing up to 500 atoms. These results are compared with analogous calculations using the well known Thomas-Fermi-Weizsäcker-Dirac (TFWD) approximations for the kinetic (TFW) and exchange (D) energy density functionals. An outstanding improvement of the total and exchange energies, of the density at the nucleus and of the 〈r-1〉 expectation values is obtained for atoms within the WDA scheme. For sodium clusters we notice a sizeable contribution of the nonlocal effects to the total energy and to the density profiles. In the limit of very large clusters these effects should affect the surface energy of the bulk metal. © 1992 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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