Contribution à l'étude de la distribution des états électroniques de NiO dans l'état fondamental : utilisation de l'approximation LSDA+U

Abstract : The electronic state distribution of the NiO antiferromagnetic ground state has been studied within the local spin density approximation. All electrons, including the localized 3D electrons, are described by means of itinerant states according to the translational symmetry. The wave functions and energies are obtained self-consistently through a spin polarized linear combination of atomic orbitals method. Unlike a classical calculation, the charge fluctuations have been taken into account and related to a potential acting specifically on the 3D electrons. The main term in that potential is the on-site electrostatic interaction U between two electrons. The presence of U alters the repartition of the allowed and forbidden electronic states as well as the degree of hybridyzation of the eigenfunctions. The results show that the occupied 3D bands are narrow and nearly separated. The calculated gap value is in agreement with the experimental value when U is adjusted to 5.4 eV. The occupied and empty 3D functions are those predicted by the ligand field applied to an atom in a cubic surrounding. The oxygen 2p bands reside below the small dispersive metallic 3D bands and confer a Mott insulating character to NiO. Nevertheless the full bands are not entirely pure because U enhances the ratio of the oxygen 2p functions within these bands. The theoretical electronic state diagram allows the interpretation of the whole experimental results particulary the optical absorption and the photoemission. Finally the satisfactory agreement with the angular photoemission spectra shows the ability of our approch to describe the ground state of NiO
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Mohamed Kamal. Contribution à l'étude de la distribution des états électroniques de NiO dans l'état fondamental : utilisation de l'approximation LSDA+U. Autre [cond-mat.other]. Université Paul Verlaine - Metz, 1995. Français. ⟨NNT : 1995METZ004S⟩. ⟨tel-01776871⟩

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