  The GW approximation is a well-known method to improve electronic structure
predictions calculated within density functional theory. In this work, we have
implemented a computationally efficient GW approach that calculates central
properties within the Matsubara-time domain using the modified version of Elk,
the full-potential linearized augmented plane wave (FP-LAPW) package.
Continuous-pole expansion (CPE), a recently proposed analytic continuation
method, has been incorporated and compared to the widely used Pade
approximation. Full crystal symmetry has been employed for computational
speedup. We have applied our approach to 18 well-studied
semiconductors/insulators that cover a wide range of band gaps computed at the
levels of single-shot G0W0, partially self-consistent GW0, and fully
self-consistent GW (scGW). Our calculations show that G0W0 leads to band gaps
that agree well with experiment for the case of simple s-p electron systems,
whereas scGW is required for improving the band gaps in 3-d electron systems.
In addition, GW0 almost always predicts larger band gap values compared to
scGW, likely due to the substantial underestimation of screening effects. Both
the CPE method and Pade approximation lead to similar band gaps for most
systems except strontium titantate, suggesting further investigation into the
latter approximation is necessary for strongly correlated systems. Our computed
band gaps serve as important benchmarks for the accuracy of the Matsubara-time
GW approach.
