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  • 1990-1994  (7)
  • 1980-1984  (6)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1295-1303 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Experimental ionization potentials (I) and electron affinities (A) of metal clusters MeN are compiled for a variety of systems and their size dependence is analyzed. In the theoretical part, we perform semiclassical density variational calculations using the spherical jellium model and the local density approximation. For alkali systems and, to some extent, also for some nonalkali systems, the calculated values of I and A reproduce very well the average size dependence of the measured quantities, if their common bulk limit W is adjusted to the experimental bulk work function. This holds even for rather small systems where I and A are no longer linear in N−1/3. We discuss the extent to which classical models for the energetics of charged metal spheres can account for the correct size dependence in the large-cluster limit. We point out that the deviation of the slope parameters α and β in the asymptotic expressions I∼W+α(e2/rs)N−1/3, A∼W−β(e2/rs)N−1/3 from the values (1)/(2) , which depends on the material via the Wigner–Seitz parameter rs, can be entirely accounted for by quantum-mechanical effects, namely the kinetic, exchange, and correlation energies and the diffuseness of the electron density.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 319 (1984), S. 205-213 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In heavy nuclei where the thickness of the diffused edge is relatively small, a certain sharp effective surface can be defined which characterizes the shape of the nucleus, and it can be considered as a collective dynamic variable. It is shown that the problem of fluid dynamics can be simplified by reducing it to simple linearized equations for the dynamics in the nuclear interior and boundary conditions set at the effective dynamic sharp surface of the density distribution. These conditions are derived from the fluid dynamical equations. Transitional densities obtained from this simple model are compared with the numerical solution of fluid dynamical equations.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 315 (1984), S. 341-347 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The single-particle densityρ(r) of a system of fermions can be calculated in a tractable way as the Laplace inverse of the Bloch density describing the system. The complex integrals involved can be solved very easily by the saddle-point method. The semiclassical nature of this approach is illustrated in the simple example of the single-particle level density of a harmonic oscillator potential. It is then applied to calculate the total energy of particles in different mean field potentials. The exact Bloch density being generally unknown, different approximate forms are used in our calculations which correspond to a partial resummation of the Wigner-Kirkwoodħ-expansion. The resulting local densities reproduce the exact density distributions on the average, without quantal oscillations. They are well defined everywhere, even beyond the classical turning point, in contrast to the original Wigner-Kirkwood approach.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 319 (1984), S. 159-165 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss the exact solution of the time-dependent Schrödinger equation for a system of two crossing levels with a residual interaction. In contrast to the familiar Landau-Zener (LZ) solution used in most applications, we allow for more general boundary conditions; in particular we treat explicitly the case of afinite interval around the crossing point. The exact jumping probability is shown to be extremely sensitive to these boundary conditions; in many realistic cases it is found to be smaller than the LZ value by several orders of magnitude. We also compare the exact excitation energy to the one obtained in the usual cranking approach.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 316 (1984), S. 217-223 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Equations of a combined, liquid plus particle model are derived which accounts consistently for the short-range liquid properties of nuclei as well as for the long-range quasi-particle behavior. Macroscopic quantities are defined as statistical averages and their dynamics is determined by an Euler-type equation, which contains a term due to the interaction with the gas component, and also by the continuity equation. For the quasi-particle component the full quantal treatment is kept in the form of the Liouville equation with a time-dependent external potential related to the bulk density. It may include the residual quasi-particle interaction. It is suggested that the solution of the coupled dynamics is facilitated by the explicit use of an effective sharp nuclear surface as a dynamical variable.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 296 (1980), S. 87-90 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Wigner-Kirkwoodℏ-expansion of the Wigner transform of the Bloch density can be resummed in the case of non local potentials if we keep only up to second order derivatives of the Wigner transform of the non-local potential with respect to the phase space variables. We also investigate a second approximation to the Bloch density where care has been taken with respect to a consistentℏ expansion. For a one dimensional example we calculate the smooth part of the density and the corresponding energy demonstrating that both approximations to the Bloch-density yield well defined average densitiesand energies.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 297 (1980), S. 247-256 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigate the semiclassical kinetic energy density functionalτ[ρ] for deformed nuclear shapes. Using Strutinsky-averaged quantities as reference, we demonstrate that the functionalτ[ρ] is able to reproduce the averaged kinetic energies very accurately, even at very large deformations.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 349 (1994), S. 219-222 
    ISSN: 1434-601X
    Keywords: 21.60.Jz ; 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss and compare the gross features of resonance excitations in nuclei and metal clusters. We point out the phenomenon of ”jellium scaling” which means that different materials for metal clusters all give similar resonance spectra and we discuss the various effects which determine the exact position of the resonance.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 17 (1990), S. 225-229 
    ISSN: 1434-6079
    Keywords: 31.20.Sy ; 03.65.Sq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A semiclassical version of the density functional approach is used to investigate the structure of metal clusters. The effect of the ionic structure is included in a schematical way, assuming that the ions are distributed on concentric shells. The method, which allows a simultaneous investigation of geometrical and electronic effects, is computationally very simple and can be extended up to very large cluster sizes. Predictions of this model in the medium size range are compared with the results of available microscopic calculations, yielding a very good agreement.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 51-53 
    ISSN: 1434-6079
    Keywords: 36.40. +d ; 31.20.Sy ; 05.30.−d ; 65.60. +m
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We apply the finite-temperature Kohn-Sham method to alkali metal clusters, using the spherical jellium model and treating the valence electrons as a canonical system in the heat bath of the ions. We study the shell effects in the total free energyF(N) and the entropyS(N) for neutral clusters containingN atoms. Their strongest temperature dependence is due to the finite ground-state valueS 0〉0 of the electronic entropy for non-magic clusters. It leads to a decreasing amplitude and an increasing smear-out of the saw-tooth structure in the first difference Δ1 F(N)=F(N−1)−F(N) with increasing temperatureT and cluster sizeN.
    Type of Medium: Electronic Resource
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