Computing total energies in complex materials using charge self-consistent DFT+DMFT

TL;DR

This paper presents a new fully charge-self-consistent DFT+DMFT methodology for calculating total energies in complex correlated materials, using plane waves and Wannier functions, validated on rare-earth nickelates.

Contribution

The paper introduces a novel charge-self-consistent DFT+DMFT approach with a generalized double counting correction, enabling accurate total energy calculations for complex materials.

Findings

Validated on rare-earth nickelates with results consistent with experiments.

Demonstrated the importance of correct double counting correction.

Compared DFT+DMFT with DFT+U, showing DFT+U's limitations.

Abstract

We have formulated and implemented a fully charge-self-consistent density functional theory plus dynamical mean field theory methodology which enables an efficient calculation of the total energy of realistic correlated electron systems. The density functional portion of the calculation uses a plane wave basis set within the projector augmented wave method enabling study of systems with large, complex unit cells. The dynamical mean field portion of the calculation is formulated using maximally localized Wannier functions, enabling a convenient implementation which is independent of the basis set used in the density functional portion of the calculation. The importance of using a correct double counting term is demonstrated. A generalized form of the standard double counting correction, which we refer to as the $U^\prime$ form, is described in detail and used. For comparison the density functional plus U method is implemented within the same framework including the generalized double counting. The formalism is validated via a calculation of the metal-insulator and structural phase diagrams of the rare-earth nickelate perovskites as functions of applied pressure and A-site rare-earth ions. The calculated density functional plus dynamical mean field results are found to be consistent with experiment. The density functional plus U method is shown to grossly overestimate the tendency for bond-disproportionation and insulating behavior.