Slightly high G0W0 quasiparticle gap

[subhayan]

Dear developer,

I am trying to calculate the G0W0 direct gap at the gamma point of solid Li2O2. I am getting a value of ~5.28 eV which is a little bit higher than the reported value of 4.81 eV (https://doi.org/10.1063/1.3645544) . However, I'm finding a PBE gap of ~1.92 eV which is in good agreement with the PBE gap of 1.94 eV reported in the same paper.

I was wondering if you could kindly take a look at the attached input and output files and let me know what you think I might be doing wrong. I ran a calculation with lower VXCRLvcs, EXXRLvcs (=24365 RL) and lower NGsBlkXp (=20) but the gap doesn't seem to change much.

Eagerly awaiting your reply,
Subhayan

[Daniele Varsano]

Dear Subhayan,

my suggestion is a careful check on the convergence, the used number of bands (54) seems to be quite small considering you have 14 occupied bands. I would run calculations using
100-200-300 bands to check the convergence.

Moreover, also the NGsBlkXp=25RL is unusually small, again I will check the convergence considering 200-400-600 RL and so on.

Best,
Daniele

[subhayan]

Hi Daniele,

Thanks a lot. I'll try that.

Best regards,
Subhayan

[subhayan]

This fixes the issue. Thanks a lot.