[DFTB-Plus-User] DFTB-Plus-User Digest, Vol 117, Issue 3

[Achyut Subedi]

Dear Professor Niehaus,

Thank you for your response.  Among the k points and corresponding orbital
energy values, how do we know which value corresponds to the band gap?
I couldn't attach my band.out file here to get more insight on it because
of size limitation.
Which value should we pick to get the band gap?
I have seen many authors reporting the band gap using DFTB+ calculation but
I am not sure how they calculate.

I would be happy to be more clear on this topic. Thank you!

On Tue, May 7, 2024 at 6:00 AM <
dftb-plus-user-request at mailman.zfn.uni-bremen.de> wrote:

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>    1. Re: Band_gap calculation in DFTB+ (Thomas Niehaus)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 6 May 2024 16:34:14 +0200
> From: Thomas Niehaus <thomas.niehaus at univ-lyon1.fr>
> To: <dftb-plus-user at mailman.zfn.uni-bremen.de>
> Subject: Re: [DFTB-Plus-User] Band_gap calculation in DFTB+
> Message-ID: <3be399f8-5753-4337-9421-bfc8ebc47d7d at univ-lyon1.fr>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> Hi,
>
> the file band.out contains the information you are looking for. It lists
> for each k-Point the orbital energy and the occupation of that
> orbital/band. Be aware that for indirect band gaps the conduction band
> minimum and the valence band maximum might be at different k-Points.
>
> Hope that helps.
>
> Best Thomas
>
> On 5/3/24 18:00, Achyut Subedi wrote:
> >
> > I am a new DFTB+ user and I am trying to calculate the band structure
> > and Density of states for a larger system.
> >
> > I have got one confusion while calculating the band gap of a band
> > structure. What I did for now is plotted the "band_tot.dat" output
> > file in MATLAB and calculated the difference between maximum valence
> > band and lowest conduction band. But, I wanted to know if we can get
> > the band gap directly from our calculation in DFTB+ as we get in DFT
> > calculation as "Highest Occupied Molecular Orbital" and "Lowest
> > Unoccupied Molecular Orbital" and find difference in between them.
> >
> >
> > I want to know if the band gap can be directly calculated by
> > manipulating the input files or there is another method for its
> > calculation.
> >
> > I can see a lot of papers reporting the band gap calculated for a
> > larger ( systems) but I am not sure how it was calculated.
> >
> >
> > --
> > Best Regards
> > Er. Achyut Subedi
> > Registered Mechanical Engineer
> > (IOE, TU, Nepal)
> > +977-9847703110
> >
> > _______________________________________________
> > DFTB-Plus-User mailing list
> > DFTB-Plus-User at mailman.zfn.uni-bremen.de
> >
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>
> --
> Prof. Dr. Thomas Niehaus
> Institut Lumière Matière
> UMR5306 CNRS
> Université Claude Bernard Lyon 1
> Domaine Scientifique de La Doua
> 10 rue Ada Byron
> 69622 Villeurbanne CEDEX, France
> --
> Office: Brillouin building, 4th floor, room 006
> Tel: +33 472 431 571
> Home page:http://ilm-perso.univ-lyon1.fr/~tniehaus
> Lab:http://ilm.univ-lyon1.fr
>
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-- 
Best Regards
Er. Achyut Subedi
Registered Mechanical Engineer
(IOE, TU, Nepal)
+977-9847703110
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