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

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 planewave 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 ${U}^{\ensuremath{'}}$ 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.