GW calculations reduce the band gap

[Guo_BIT]

Dear developers：
In my calculation, the GW correction reduces the bandgap. I’m not sure if this result is reasonable or if it is due to an issue with my input files.
I have attached my GW input file and results. Thank you in advance

[Daniele Varsano]

Dear Jingda Guo,

this is indeed rather unusual. I would anyway carefully check the convergences.
Here goes some suggestions.

1. VXCRLvcs possibly should be kept to the maximum number of G vectors (cutoff of the density)
2. EXXRLvcs, check the convergence, this is not time and memory intensive and can be raised
3. Number of bands in X and G, even if you used a terminator technique, check if it is at convergence
4. if your pseudopotential have non-linear core correction, you need to activate them to take into account with the keyword: UseNLCC
5. If your system is a 2D material, you want to use the coulomb cutoff technique in order to speed up convergence with repsect the amount of vacuum needed to isolate the monolyaer.


Not related with the result:
In X and SE parallelization, avoid parallelization over "q" as it could bring unbalances. In general, push as you can the parallelization over bands "c" and "v" in X and "b" in SE.

Best,

Daniele