[QE-users] Assunto: Re: Assunto: Re: Difference in Fermi energy by increasing k-points

[Paolo Giannozzi]

The two figures are exactly the same, only the origin of the x axis is
shifted.

Paolo

On Tue, Jan 4, 2022 at 10:29 AM José Xavier via users <
users at lists.quantum-espresso.org> wrote:

> Dear Nishidate,
>
> Thank you for your answer.
>
> I don't know if I understood... Could you explain me better what should I
> do, please?
>
> I'm sending a figure of my DOS plotted using the HOMO and the EFermi as
> the zero, respectively, to make my doubt clearer.
>
> I learned that I should use a "large" number of k-points to converge the
> system. However, I only found the first figure when I used the 10x10x10
> k-points in the NSCF calculation, and 2x2x2, 4x4x4 or 6x6x6 in the SCF.
> When I increased or decreased the k-points in the NSCF, it showed me the
> second figure (that is different from the reference one).
>
> I tried to use the smearing occupations. In this test, the EFermi in SCF
> and NSCF calculations were the same (2.74 eV), except when I used 10x10x10
> k-points in the NSCF. In this case, the EFermi was 2.74 in SCF and 1.04 eV
> in the NSCF (it is the same value that I found previously as the HOMO in
> SCF calculation).
>
> My main question is: Why is this 10x10x10 a "magic number"?
>
> Best wishes.
> I wish you a happy new year.
>
> José Xavier
>
>
> >
> >
> > Em qua., 29 29e dez. 29e 2021 às 18:22, Kazume NISHIDATE
> > <nisidate at iwate-u.ac.jp> escreveu:
>
>
> >
> >
> >
> >
>
>
>
> Dear Xavier
>
> > When I used the k-points 4x4x4 (SCF) and 8x8x8 (NSCF), the HOMO and
> > EFermi were different, and using EFermi to subtract the values in the
>
> If the k-point mesh you selected covers the typical energy peaks of
> the valence band maximum (VBM or the HOMO in your description) depends
> on the shape of Brillouin zone (BZ) of your system.
>
> You should try to plot the band structure and assess the VBM and find
> out its k-point location. If the k-point mesh you selected does not
> cover the k-point, then the VBM peak will not contribute to your DOS
>
> plot.
>
>
>
>
>
> 敬具 西館
>
> best regards
>
>
>
> nisidate at iwate-u.ac.jp
>
> kazume.nishidate at gmail.com
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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