The nature of the electronic band gap in lanthanide oxides

TL;DR

This paper evaluates hybrid density functionals and screened-exchange methods for accurately predicting the electronic band gaps of lanthanide oxides, showing they match well with experimental data and recent advanced calculations.

Contribution

It demonstrates that hybrid density functionals and sX-LDA effectively model strongly correlated f-electrons and predict band gaps in lanthanide oxides, aligning with experimental results.

Findings

HSE functionals accurately predict band gaps across the lanthanide series.

sX-LDA better estimates unoccupied 4f levels, improving agreement with experiments.

Band gap trends depend on the position of 4f states relative to other bands.

Abstract

Accurate electronic structures of the technologically important lanthanide/rare earth sesquioxides (Ln2O3, with Ln=La,...,Lu) and CeO2 have been calculated using hybrid density functionals HSE03, HSE06 and screened-exchange (sX-LDA). We find that these density functional methods describe the strongly correlated Ln f-electrons as well as the recent G0W0@LDA+U results, generally yielding the correct band gaps and trends across the Ln-period. For HSE, the band gap between O 2p states and lanthanide 5d states is nearly independent of the lanthanide, while the minimum gap varies as filled or empty Ln 4f states come into this gap. sX-LDA predicts the unoccupied 4f levels at higher energies, which leads to a better agreement with experiments for Sm2O3, Eu2O3 and Yb2O3.