Band convergence and linearization error correction of all-electron GW calculations: The extreme case of zinc oxide

TL;DR

This paper improves all-electron GW calculations for ZnO by addressing band convergence and linearization errors, leading to more accurate band gap predictions that differ from previous studies.

Contribution

It introduces a method to correct linearization errors and extrapolate band gaps to infinite bands in GW calculations for ZnO.

Findings

Band gap converges more slowly than previously thought.

Linearization error significantly affects high-lying states.

Corrected calculations yield larger band gaps than earlier results.

Abstract

Recently, Shih et al. [Phys. Rev. Lett. 105, 146401 (2010)] published a theoretical band gap for wurtzite ZnO, calculated with the non-selfconsistent GW approximation, that agreed surprisingly well with experiment while deviating strongly from previous studies. They showed that a very large number of empty bands is necessary to converge the gap. We reexamine the GW calculation with the full-potential linearized augmented-plane-wave method and find that even with 3000 bands the band gap is not completely converged. A hyperbolical fit is used to extrapolate to infinite bands. Furthermore, we eliminate the linearization error for high-lying states with local orbitals. In fact, our calculated band gap is considerably larger than in previous studies, but somewhat smaller than that of Shih et al..