Abstract
In order to promote our understanding on electronic structure of actinide dioxides, we construct a tight-binding model composed of actinide 5f and oxygen 2p electrons, which is called f-p model. After the diagonalization of the f-p model, we compare the eigen-energies in the first Brillouin zone with the results of relativistic band-structure calculations. Here we emphasize a key role of f-p hybridization in order to understand the electronic structure of actinide dioxides. In particular, it is found that the position of energy levels of Г7 and Г8 states determined from crystalline electric field (CEF) potentials depends on the f-p hybridization. We investiagte the values of the Slater-Koster integrals for f-p hybridization, (fpσ) and (fpπ), which reproduce simultaneously the local CEF states and the band-structure calculation results. Then, we find that the absolute value of (fpπ) should be small in comparison with (fpσ) = 1 eV. The small value of |(fpπ)| is consistent with the condition to obtain the octupole ordering in the previous analysis of the f-p model.
Highlights
Actinide dioxides form a group of important materials from technological viewpoints of a nuclear reactor fuel and a heterogeneous catalyst
In order to clarify the role of f-p hybridization for the appearance of octupole ordering, Maehira and Hotta have performed the band-structure calculations for actinide dioxides by a relativistic linear augmented-plane-wave method with the exchange-correlation potential in a local density approximation [21]
In order to reproduce the result of the relativistic bandstructure calculations and obtain the electronic structure consistent with the local crystalline electric field (CEF) state, we find that the Slater-Koster parameters for f-p hybridization should be limited in a certain range
Summary
Actinide dioxides form a group of important materials from technological viewpoints of a nuclear reactor fuel and a heterogeneous catalyst. From the crystal structure of actinide dioxides, it is important to include explicitly 2p electrons, since actinide ion is surrounded by eight oxygens and the main hopping process between nearest neighbor sites should occur from the f-p hybridization. In this sense, f-p model is more realistic Hamiltonian for actinide dioxides. In order to clarify the role of f-p hybridization for the appearance of octupole ordering, Maehira and Hotta have performed the band-structure calculations for actinide dioxides by a relativistic linear augmented-plane-wave method with the exchange-correlation potential in a local density approximation [21].
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