[Pw_forum] Fermi energy

[Andrea Ferretti]

Dear Yang,

The computed fermi energy depends on the adopted kpt grid.
Fermi energy is computed in scf runs (assuming occupations are not 
"fixed") and re-computed in nscf runs and differences can arise due to 
differences in the scf and nscf kpt meshes...

Note that nscf calculations are meant to deal with summations over 
the Brillouin zone, which means that kpts and their weight must be 
chosen accordingly.
if instead you want eg to compute quantities at specific kpoints 
(a typical example is the band structure), your kpt summations might lose 
a lot of accuracy and the estimation of the fermi energy along with that 
(in this case use calculation="bands" instead)

hope it helps
andrea

>
> I have a problem with the estimated Fermi energy in the scf and nscf
> calculation toward
> a slab structure metal. I found that the scf gives a much higher Fermi
> energy than the one
> in the nscf calculation. Anybody has idea about this?
>
> Best regards,
>
> Yang
>
>
>

-- 
Andrea Ferretti
MIT, Dept Material Science & Engineering
bldg 13-4078, 77, Massachusetts Ave, Cambridge, MA
Tel: +1 617-452-2455;  Skype: andrea_ferretti
URL: http://quasiamore.mit.edu

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