Modelization of Alkali Metal Clusters in Density Functional Theory

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Different aspects of the physics of atomic clusters are discussed in a common framework, namely the jellium model. The discussion is concentrated on alkali metal clusters. Various versions of the jellium model are examined depending whether the interactions between ions and valence electrons are described by the point-like Coulomb interaction, a pseudopotential or a pseudohamiltonian. These versions lead to different energy density functionals from which one can derive the Kohn-Sham equations describing static properties, and the timedependent local density approximation (TDLDA) describing excitation spectra of clusters. The numerical solutions of Kohn-Sham equations are used to calculate mean potentials, ionization potentials and shell structure in various clusters as well as supershell phenomena in large (N sime 1000 - 5000) clusters. Next, the linear response of clusters is studied by solving TDLDA/RPA equations. Calculated dipole plasmons are compared with experimental systematics. The influence of spillout effect and electron effective mass on calculated plasmon energies are also discussed in terms of sum rules. For the limiting case of plasmon in bulk metals with the ion-electron interaction described by a realistic non-local pseudopotential, an analytic calculation shows the lowering of plasmon frequency due to the increase of effective mass. Finally ground state correlations in clusters are examined from two different viewpoints, first by calculating the occupation numbers of electrons in the correlated ground state, and then by looking at the possible existence of harmonic double plasmons. It is found that occupation numbers can depart somewhat from their uncorrelated limits and that strong anharmonicities occur in the multiplasmon spectra, thus indicating strong ground state correlations.
理論物理学刊行会の論文
1997-02-25

Modelization of Alkali Metal Clusters in Density Functional Theory

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