[Wien] Confusion about DOS
Peter Blaha
pblaha at theochem.tuwien.ac.at
Sat Nov 27 16:10:18 CET 2021
> Is this a calculation with just one k-point ?
>
> Yes. It is a calculation with one k point
Then everything is clear.
Obviously, with one k-point in the BZ one cannot use the tetrahedra
method. There are no bands (E as funktion of k), but just one eigenvalue
"per band". In principle, your DOS consists of a number of
delta-functions. So tetra switches automatically to a broadening method
(Gaussian by default) with some broadening (see description of tetra and
case.int in UG).
With a broadening method of course also your VBM (CBM) will be broadened
and this is what you see in the DOS.
Of course, a single k-point calculation is valid only for very large
supercells....
>
>
> look into case.outputt
>
>
> Near Fermi Energy:
> case.outputtup: 0.00086 664.55 40.0000 0.37 0.0208
> case.outputtdn: 0.00886 851.95 46.0000 0.28 0.0244
>
>
> These are data without broadening and you should see how many electrons
> (integral of DOS, 3rd column) are up to EF.
>
> In addition, check out the :BAND ranges in scf2
> You should see a correspondence of those with the DOS (in Ry).
>
> There are 217 bands
>
> Looking forward to your response.
>
> with regards,
>
>
> Am 27.11.2021 um 14:08 schrieb shamik chakrabarti:
> > Yes, the gap 2.875 eV is the value found from SCF. I have tried with
> > broadening 0.001 & also with 0.000...however, it shows no
> improvement.
> > Is it due to numerical noise & can be neglected?
> >
> > On Sat, 27 Nov 2021 at 18:30, Tran, Fabien
> <fabien.tran at tuwien.ac.at <mailto:fabien.tran at tuwien.ac.at>
> > <mailto:fabien.tran at tuwien.ac.at
> <mailto:fabien.tran at tuwien.ac.at>>> wrote:
> >
> > Is 2.875 eV the value of :GAP in case.scf? If yes, it looks
> like if
> > the Fermi energy
> > is not placed correctly on the DOS, because the gap between the
> > valence and
> > conduction band seems to be close to 2.875 eV.
> > Could it be due to the broadening in case.int
> <http://case.int> <http://case.int <http://case.int>>? Try
> > to execute tetra with a reduced (or no) broadening.
> >
> > ________________________________________
> > From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at
> <mailto:wien-bounces at zeus.theochem.tuwien.ac.at>
> > <mailto:wien-bounces at zeus.theochem.tuwien.ac.at
> <mailto:wien-bounces at zeus.theochem.tuwien.ac.at>>> on behalf of
> > shamik chakrabarti <shamik15041981 at gmail.com
> <mailto:shamik15041981 at gmail.com>
> > <mailto:shamik15041981 at gmail.com
> <mailto:shamik15041981 at gmail.com>>>
> > Sent: Saturday, November 27, 2021 7:54 AM
> > To: A Mailing list for WIEN2k users
> > Subject: [Wien] Confusion about DOS
> >
> > Dear Wien2k users,
> >
> > I have plotted DOS for material with
> converged
> > SCF using HSE06. I got a bandgap of 2,875 eV. However, in the
> > plotted DOS it can be seen that a small amount of DOS from the
> > valence band is crossing the Fermi energy. I have attached
> the plot
> > to this mail.
> >
> > Is this crossing can be neglected or I should have to change some
> > other parameters like broadening etc.
> >
> > with regards,
> >
> > --
> > Dr. Shamik Chakrabarti
> > Research Fellow
> > Department of Physics
> > Indian Institute of Technology Patna
> > Bihta-801103
> > Patna
> > Bihar, India
> > _______________________________________________
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> >
> >
> >
> > --
> > Dr. Shamik Chakrabarti
> > Research Fellow
> > Department of Physics
> > Indian Institute of Technology Patna
> > Bihta-801103
> > Patna
> > Bihar, India
> >
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>
> --
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
> Email: blaha at theochem.tuwien.ac.at
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>
> --
> Dr. Shamik Chakrabarti
> Research Fellow
> Department of Physics
> Indian Institute of Technology Patna
> Bihta-801103
> Patna
> Bihar, India
>
> _______________________________________________
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at WIEN2k: http://www.wien2k.at
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