Core-level shifts and their relation to surface effects and dimensionality of a system

Document Type

Article

Publication Date

12-6-1998

Department

Department of Physics

Abstract

In the spirit of Jean-Louis Calais's endeavor to effectively combine the tools of quantum chemistry and solid-state physics to study the electronic structure of materials, Hartree-Fock calculations of core-level binding energy shifts in Li chains and Li slabs and their relation to surface effects, charge oscillations, and dimensionality of a system are presented. For the one-dimensional system the 1s binding energy oscillates regularly from the edge Li atom to the center, the 1s level of the edge atom being shifted to a larger binding energy. For two-dimensional Li slabs which model the (001) surface of Li, the 1s level of the top layer atom is found to have the largest binding energy, being ∼ 0.5 eV below the 1s levels of the other layers, and the binding energy is constantly decreasing from the surface to the bulk, independent of the charge population and without oscillations. Both Mulliken population analysis and charge difference plots indicate that the edge atom in the chain is positively charged, whereas the surface atoms in the slab are negatively charged. This shows that a positive or negative net valence population alone does not determine the direction of the shifts. The predicted core-level binding energy shifts should be observable with high-resolution synchroton measurements. The distinct differences predicted for core-level shifts for one- and two-dimensional systems can be used to characterize and probe the geometry of nanostructures.

Publication Title

International Journal of Quantum Chemistry

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