2008-11-03 9806788.Pdf
Abstract The linear response function, which describes the change in the electron density induced by a change in the external potential, is the basis for a broad variety of applications. Three of these are addressed in the present thesis. In the first part, optical spectra of metallic surfaces are investigated. Quasiparticle energies, i.e., energies required to add or remove an electron from a system, are evaluated for selected metals in the second part. The final part of this thesis is devoted to an improved description of the ground-state electron correlation energy. In the first part, the linear response function is used to evaluate optical properties of metallic surfaces. In recent years, reflectance difference (RD) spectroscopy has provided a sensitive experimental method to detect changes in the surface structure and morphology. The interpretation of the resulting spectra, which are linked to the anisotropy of the surface dielectric tensor, however, is often difficult. In the present thesis, we simulate RD spectra for the bare, as well as oxygen and carbon monoxide covered, Cu(110) surface, and assign features in these spectra to the corresponding optical transitions. A good qualitative agreement between our RD spectra and the experimental data is found. Density functional theory (DFT) gives only access to the ground state energy. Quasi- particle energies should, however, be addressed within many body perturbation theory. In the second part of this thesis, we investigate quasiparticle energies for the transition metals Cu, Ag, Fe, and Ni using the Green’s function based GW approximation, where the screened Coulomb interaction W is linked to the linear response function.
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