[QE-users] Query regarding k path selection, mismatching of band gap
Vahid Askarpour
vh261281 at dal.ca
Tue Oct 13 23:14:01 CEST 2020
I think for insulators, occupation =fixed in the scf calculation. The degauss value is mainly for metals. You are using a broadening of 0.02Ry=0.272eV for a gap which is only 0.04eV. This broadening will likely result in a metallic DOS, which is what you are getting. For the nscf/DOS calculation, I suggest the tetrahedron method. These are explained in the QE manual.
Cheers,
Vahid
Vahid Askarpour
Department of physics and atmospheric science
Dalhousie University
Halifax, NS
On Oct 13, 2020, at 4:49 PM, Poonam Kaushik <poonamkaushik40 at gmail.com<mailto:poonamkaushik40 at gmail.com>> wrote:
CAUTION: The Sender of this email is not from within Dalhousie.
Dear Expert,
About the first option, I used to confuse to select the correct option for the occupation, smearing type, and broadening part. In my input file, I used an 'mv' smearing with a broadening of 0.02 Ry. So either I can reduce it to 0.01 Ry or I can try any other occupation, like tetrahedra or fixed. my system is an insulator with a small bandgap of 0.04 eV. Also in the third option, I calculated the k path by using the CIF file, and k-pathfinder. Please correct me if I am wrong.
Thanks and regards,
Poonam Sharma
-------------------------------------------------------------------------------------------------
Poonam Sharma
Research Scholar
Department of Physics
Indian Institute of Technology Bombay
Mumbai - 400076
India.
On Wed, Oct 14, 2020 at 12:18 AM Nicola Marzari <nicola.marzari at epfl.ch<mailto:nicola.marzari at epfl.ch>> wrote:
On 13/10/2020 20:43, Poonam Kaushik wrote:
> Dear Expert,
> So the only option that I have is to include the complete path and do
> the calculation again.
> Thank you so much for your suggestion.
>
Mostly welcome, but you have three options - destiny can be generous
sometimes.
The first option would be doing a more careful DOS:
https://www.quantum-espresso.org/Doc/INPUT_DOS.html
nicola
>
>
> Thanks and regards,
> Poonam Sharma
>
>
>
>
> -------------------------------------------------------------------------------------------------
> Poonam Sharma
> Research Scholar
> Department of Physics
> Indian Institute of Technology Bombay
> Mumbai - 400076
> India.
>
>
>
> On Tue, Oct 13, 2020 at 11:53 PM Nicola Marzari <nicola.marzari at epfl.ch<mailto:nicola.marzari at epfl.ch>
> <mailto:nicola.marzari at epfl.ch<mailto:nicola.marzari at epfl.ch>>> wrote:
>
>
>
>
> From the most to the less likely, it could be that your DOS has some
> broadening that masks the existence of a small gap, or that the gap
> closes across the last two segments of the path that you are
> missing, or
> that you are very unlucky and the band gaps closes at points that do
> not
> lie on a high symmetry path.
>
> nicola
>
>
> On 13/10/2020 19:53, Poonam Kaushik wrote:
> >
> > Dear Experts,
> > I have one query regarding k path selection. After using Kpath
> finder
> > (https://www.materialscloud.org/work/tools/seekpath ), i got
> this type
> > of k path
> > G-M-K-G-A-L-H-A|L-M|H-K for my structure. In the calculation, I
> used, up
> > to G-M-K-G-A-L-H-A. So, is this ok to select a path up to this?
> > Basically in the band structure, I am getting some finite gap
> while in
> > dos I m getting a zero bandgap, after selecting the path up to
> > G-M-K-G-A-L-H-A. I am not able to figure out why this is happening?
> > Should it help to include the complete path? I am attaching here my
> > input file, band structure, and dos. Please have a look.
> >
> >
> https://drive.google.com/drive/folders/1UhUgod8KnvdovJfxMqbJMQwdtb3dE-yY
> >
> > I'll be very thankful for any suggestions.
> >
> > Thanks and regards,
> > Poonam Sharma
> >
> >
> >
> >
> -------------------------------------------------------------------------------------------------
> > Poonam Sharma
> > Research Scholar
> > Department of Physics
> > Indian Institute of Technology Bombay
> > Mumbai - 400076
> > India.
> >
> >
> > _______________________________________________
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>
> --
> ----------------------------------------------------------------------
> Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
> Director, National Centre for Competence in Research NCCR MARVEL, EPFL
> http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project
>
--
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project
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