Key role of hybridization between actinide 5f and oxygen 2p orbitals for electronic structure of actinide dioxides

TL;DR

This paper constructs a tight-binding $f$-$p$ model to highlight the crucial role of actinide 5f and oxygen 2p orbital hybridization in determining the electronic structure of actinide dioxides, aligning with relativistic band calculations.

Contribution

It introduces a novel $f$-$p$ hybridization model that clarifies the influence of orbital interactions on energy levels and electronic properties of actinide dioxides.

Findings

$f$-$p$ hybridization significantly affects energy level positions.

The model explains the dependence of $ ext{Γ}_7$ and $ ext{Γ}_8$ states on hybridization.

Conditions for hybridization relate to octupole ordering in NpO$_2$.

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 eigenenergies 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 $\Gamma_7$ and $\Gamma_8$ states determined from crystalline electric field potentials depends on the $f$-$p$ hybridization. We clarify the condition on the $f$-$p$ hybridization to explain the electronic structure which is consistent with the local crystalline electric field state. We briefly discuss the region of the absolute values of the Slater-Koster integrals for $f$-$p$ hybridization concerning the appearance of octupole ordering in NpO$_2$.