Core electron excitations in U4+: modelling of the nd105f2→ nd95f3transitions with n = 3, 4 and 5 by ligand field tools and density functional theory
| Autor: | Claude Daul, Johannes Bertsch, Harry Ramanantoanina, Goutam Kuri |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Ligand field theory
Coupling constant Hubbard model Chemistry General Physics and Astronomy 02 engineering and technology Electronic structure 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences Core electron Atomic orbital Electron excitation Density functional theory Physical and Theoretical Chemistry Atomic physics 0210 nano-technology |
| Zdroj: | Physical Chemistry Chemical Physics. 18:19020-19031 |
| ISSN: | 1463-9084 1463-9076 |
| Popis: | Ligand field density functional theory (LFDFT) calculations have been used to model the uranium M4,5, N4,5 and O4,5-edge X-ray absorption near edge structure (XANES) in UO2, characterized by the promotion of one electron from the core and the semi-core 3d, 4d and 5d orbitals of U(4+) to the valence 5f. The model describes the procedure to resolve non-empirically the multiplet energy levels originating from the two-open-shell system with d and f electrons and to calculate the oscillator strengths corresponding to the dipole allowed d(10)f(2)→ d(9)f(3) transitions appropriate to represent the d electron excitation process. In the first step, the energy and UO2 unit-cell volume corresponding to the minimum structures are determined using the Hubbard model (DFT+U) approach. The model of the optical properties due to the uranium nd(10)5f(2)→nd(9)5f(3) transitions, with n = 3, 4 and 5, has been tackled by means of electronic structure calculations based on the ligand field concept emulating the Slater-Condon integrals, the spin-orbit coupling constants and the parameters of the ligand field potential needed by the ligand field Hamiltonian from Density Functional Theory. A deep-rooted theoretical procedure using the LFDFT approach has been established for actinide-bearing systems that can be valuable to compute targeted results, such as spectroscopic details at the electronic scale. As a case study, uranium dioxide has been considered because it is a nuclear fuel material, and both atomic and electronic structure calculations are indispensable for a deeper understanding of irradiation driven microstructural changes occurring in this material. |
| Databáze: | OpenAIRE |
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