Cerium Oxides without $U$: The Role of Many-Electron Correlation

TL;DR

This paper benchmarks advanced many-electron ab initio methods for accurately predicting electron transfer energies in cerium oxide, outperforming common DFT approaches and enabling improved modeling of strongly correlated materials.

Contribution

It introduces the first benchmark of ab initio many-electron theory for cerium oxide, demonstrating superior accuracy over traditional DFT methods and enabling parameter-free assessments.

Findings

Random phase approximation outperforms DFT variations.

Second-order Møller-Plesset perturbation theory recovers hybrid functional results.

Parameter-free methods enable accurate benchmarking and machine-learning applications.

Abstract

Electron transfer with changing occupation in the 4f subshell poses a considerable challenge for quantitative predictions in quantum chemistry. Using the example of cerium oxide, we identify the main deficiencies of common parameter-dependent one-electron approaches, such as density functional theory (DFT) with a Hubbard correction, or hybrid functionals. As a response, we present the first benchmark of ab initio many-electron theory for electron transfer energies and lattice parameters under periodic boundary conditions. We show that the direct random phase approximation clearly outperforms all DFT variations. From this foundation, we, then, systematically improve even further. Periodic second-order M{\o}ller-Plesset perturbation theory meanwhile manages to recover standard hybrid functional values. Using these approaches to eliminate parameter bias allows for highly accurate benchmarks of strongly correlated materials, the reliable assessment of various density functionals, and functional fitting via machine-learning.