Electronic Properties of Cerium Oxides:Towards an Effective Valence Model Hamiltonian (original) (raw)

Abstract

The primary aim of this thesis is to develop a minimal model Hamiltonian to describe the electronic properties of ceria (CeO$_{2}$) and its reduced phases. In order to do this, several energy scales of the problem were explored to determine their relative significance to the problem. These included the crystal electric field ($\Delta_{CEF}$), the spin-orbit coupling ($\lambda_{so}$), electron hopping ($t$), on-site Coulomb repulsion for the Ce 4f4f4f states ($U$), the reorganization energy ($\lambda_{0}$), the direct exchange ($J$) and the energy gap between the oxygen valence band level and the cerium 4f4f4f states ($\Gamma\epsilon$). Once the relative magnitudes of the various energy scales were determined, it was then possible to define a minimal set of degrees of freedom required to obtain a meaningful description of the system in the minimal model. The first task was to obtain baseline data for both CeO$_{2}$ and Ce$_{2}$O$_{3}$ as well as the metallic phases of Ce. Density Functio...

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