Issue 44, 2023

Strengths of covalent bonds in LnO2 determined from O K-edge XANES spectra using a Hubbard model

Abstract

In LnO2 (Ln = Ce, Pr, and Tb), the amount of Ln 4f mixing with O 2p orbitals was determined by O K-edge X-ray absorption near edge (XANES) spectroscopy and was similar to the amount of mixing between the Ln 5d and O 2p orbitals. This similarity was unexpected since the 4f orbitals are generally perceived to be “core-like” and can only weakly stabilize ligand orbitals through covalent interactions. While the degree of orbital mixing seems incompatible with this view, orbital mixing alone does not determine the degree of stabilization provided by a covalent interaction. We used a Hubbard model to determine this stabilization from the energies of the O 2p to 4f, 5d(eg), and 5d(t2g) excited charge-transfer states and the amount of excited state character mixed into the ground state, which was determined using Ln L3-edge and O K-edge XANES spectroscopy. The largest amount of stabilization due to mixing between the Ln 4f and O 2p orbitals was 1.6(1) eV in CeO2. While this energy is substantial, the stabilization provided by mixing between the Ln 5d and O 2p orbitals was an order of magnitude greater consistent with the perception that covalent bonding in the lanthanides is largely driven by the 5d orbitals rather than the 4f orbitals.

Graphical abstract: Strengths of covalent bonds in LnO2 determined from O K-edge XANES spectra using a Hubbard model

Supplementary files

Article information

Article type
Edge Article
Submitted
29 Jun 2023
Accepted
25 Oct 2023
First published
03 Nov 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2023,14, 12784-12795

Strengths of covalent bonds in LnO2 determined from O K-edge XANES spectra using a Hubbard model

W. W. Lukens, S. G. Minasian and C. H. Booth, Chem. Sci., 2023, 14, 12784 DOI: 10.1039/D3SC03304J

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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