  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..
