Electronic structure of LaBr3 from quasi-particle self-consistent GW calculations

TL;DR

This study employs the quasi-particle self-consistent GW method to accurately determine the electronic structure of LaBr_3, effectively capturing complex interactions like spin-orbit coupling and f-d state behavior, surpassing standard DFT approaches.

Contribution

The paper demonstrates the effectiveness of the parameter-free QPscGW method in accurately modeling LaBr_3's electronic structure, including spin-orbit effects and state ordering, and benchmarks it against other computational techniques.

Findings

QPscGW accurately reproduces LaBr_3's band gap and state ordering.

Spin-orbit coupling is effectively included self-consistently.

Provides a reliable basis for studying excited states and activator ions.

Abstract

Rare-earth based scintillators in general and lanthanum bromide (LaBr_3) in particular represent a challenging class of materials due to pronounced spin-orbit coupling and subtle interactions between d and f states that cannot be reproduced by standard density functional theory (DFT). Here a detailed investigation of the electronic band structure of LaBr_3 using the quasi-particle self-consistent GW (QPscGW) method is presented. This parameter-free approach is shown to yield an excellent description of the electronic structure of LaBr_3. Specifically it is able to reproduce the band gap, the correct level ordering and spacing of the 4f and 5d states, as well as the spin-orbit splitting of La-derived states. The QPscGW results are subsequently used to benchmark several computationally less demanding techniques including DFT+U, hybrid exchange-correlation functionals, and the G_0W_0 method. Spin-orbit coupling is included self-consistently at each QPscGW iteration and maximally localized Wannier functions are used to interpolate quasi-particle energies. The QPscGW results provide an excellent starting point for investigating the electronic structure of excited states, charge self-trapping, and activator ions in LaBr_3 and related materials.