[Pw_forum] Fermi energy in 'scf' and 'nscf'(XQ Wang)

lan haiping lanhaiping at gmail.com
Wed Aug 13 18:09:50 CEST 2008

dear hande,
i do wonder a point about fermi energy.
when we draw a bands along high symmetry points, which
values of fermi energy we should do align with ?  the situation of 'nscf'
calculation with large BZ sampling ,or just
the 'bands' calculation along the high symmetry points ?

On Wed, Aug 13, 2008 at 8:22 PM, Hande Ustunel <
hande at newton.physics.metu.edu.tr> wrote:

> Dear Prasenjit,
> > If the difference in Fermi energy is quite large, what I would suggest is
> to
> > increase the no. of k-points in the nscf cal. & redo it.
> The fact that Guoying's nscf calculation was conducted along high symmetry
> points suggests that it was to be followed by a band structure run. In that
> case, it is not necessary to try to obtain a "good" Fermi energy from the
> nscf run other than convince oneself since this is not the point
> here. Besides, I don't think increasing the number of kpoints along these
> high symmetry directions would mean much because since you would still have
> a severely heterogeneous sampling. It should just sufficient to just draw
> the band structure from nscf along with the Fermi energy from the scf
> calculation. But you would be absolutely right if what we were trying to do
> here was to, say, increase resolution in a DOS plot.
> On a separate note, I suggest that you try bands rather than nscf if you
> are trying to draw a band structure since nscf worries about symmetries and
> creates extra points whereas bands just does the ones you ask it to do.
> Best,
> Hande
> --
> Hande Toffoli
> Department of Physics
> Office 439
> Middle East Technical University
> Ankara 06531, Turkey
> Tel : +90 312 210 3264
> http://www.physics.metu.edu.tr/~hande<http://www.physics.metu.edu.tr/%7Ehande>
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Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn
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