[Pw_forum] A problem with HOMO and LUMO for CdS

[Nicola Marzari]

Not sure,

but:

k-points are weird: 20x20x1 for a bulk system - 20x20x20 or 20x20x16 
would seem more sensible

128 bands means 256 electrons in your unit cell - but you have only
4 atoms. Better leave it undeclared, so that the code calculates those
for you.

Also, maybe Troullier-Martins pseudos are not the best choice - look
at the SSSP tables to choose them, and remember that if 
not-normconserving ecutrho needs to be quite a bit larger than 4 times
ecutwfc - 6 to 12 times, typically. SSSP will tell you the optimal cutoff.

Last, which structure did you use? The code doesn't find any symmetry 
operation, and that's also suspicious.

				nicola




On 06/06/2017 10:49, Olga Sedelnikova wrote:
> Dear Sir,
> 
> I have made a scf calculation for wurtzite CdS. After  convergence, I 
> found that the  HOMO lies above the LUMO
> (highest occupied, lowest unoccupied level (ev):     9.9201    8.8829).
> 
> Could you suggest the source of such strange result?
> 
> -- 
> Thanks and regards,
> Olga Sedelnikova
> Nikolaev Institute of Inorganic Chemistry of SB RAS, Novosibirsk, Russia
> 
> 
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-- 
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project