Elimination of the linearization error in GW calculations based on the linearized augmented-plane-wave method

TL;DR

This paper presents a method to eliminate linearization errors in GW calculations using an extended LAPW basis set with local orbitals, improving the accuracy of quasiparticle energies and unoccupied state descriptions.

Contribution

The authors introduce local orbitals based on higher energy derivatives to fully complete the LAPW basis, removing linearization errors in GW calculations.

Findings

Linearization errors are eliminated with the extended basis.

Correlation contributions and unoccupied states are better described.

Band gaps are slightly increased, e.g., 0.03 eV for Si.

Abstract

This paper investigates the influence of the basis set on the GW self-energy correction in the full-potential linearized augmented-plane-wave (LAPW) approach and similar linearized all-electron methods. A systematic improvement is achieved by including local orbitals that are defined as second and higher energy derivatives of solutions to the radial scalar-relativistic Dirac equation and thus constitute a natural extension of the LAPW basis set. Within this approach linearization errors can be eliminated, and the basis set becomes complete. While the exchange contribution to the self-energy is little affected by the increased basis-set flexibility, the correlation contribution benefits from the better description of the unoccupied states, as do the quasiparticle energies. The resulting band gaps remain relatively unaffected, however; for Si we find an increase of 0.03 eV.