For a metal, certainly only EF from the scf calculation is ok.
For an insulator/semiconductor, we give EF at the valence band maximum.
This could be at Gamma, or at some other k-point in the BZ.
If the VBM is at Gamma and you use a shifted k-mesh, you do not have
Gamma in your scf-mesh and thus the EF from the scf calculation will be
too low, while EF from the bandstructure (when it includes Gamma) is the
correct one.
On the other hand, if the VBM is at some other k-point (eg. L), but you
plot the bands from Gamma-X only, this EF is NOT correct either, but
maybe the scf-EF is better (correct).
So in essence: there is no "simple" answer 1) or 2) is correct, but you
must "think".
Regards
On 5/29/19 4:23 AM, 徐远骥 wrote:
Dear WIEN2k users：
When I plot band structures in some cases， the value of the Fermi
level ':FER' are not the same in case.scf and case.scf2(up). In some
cases, the difference can be get large to 0.1 eV.
Which one should I need to use ?
In my understanding, the ':FER' in case.scf should be more precise,
because we using all the k-points to calculate the Fermi
energy. However, in band plot(-band) mode, we only using the k
point along high-symmetry path. In fact, I don't know how to calculate
Fermi level in case.scf2(up) in band plot mode.
What makes me confusing is: in one semiconductor type material
calculation, using scf2 Fermi energy can give a nice gap. But the Fermi
energy in case.scf will causing a little touch of Fermi level to the top
of valence band.
Best regards!
_______________________________________________
Wien mailing list
Wien@zeus.theochem.tuwien.ac.at
http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
SEARCH the MAILING-LIST at:
http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
--
P.Blaha
--------------------------------------------------------------------------
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: bl...@theochem.tuwien.ac.at WIEN2k: http://www.wien2k.at
WWW: http://www.imc.tuwien.ac.at/TC_Blaha
--------------------------------------------------------------------------
_______________________________________________
Wien mailing list
Wien@zeus.theochem.tuwien.ac.at
http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
SEARCH the MAILING-LIST at:
http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
