[DFTB-Plus-User] DFTB-Plus-User Digest, Vol 118, Issue 5

[Bálint Aradi]

Dear Achyut,

first, please note, that this mailing list (as well as the 
issues/questions section on GitHub in the DFTB+ repo) are mainly 
provided to offer discussions about DFTB+ specific questions. They are 
definitely not the right forum for obtaining basic knowledge on solid 
state physics and atomistic simulations in general. For latter ones, 
please consult more advanced fellows in your local research group or 
some books on the topic. You will gain a much deeper understanding in 
the theoretical backgrounds as from fragmented email conversations.

The quick answer to your specific question: The Fermi-level should be 
taken from the self-consistent calculation with the proper (converged) 
k-point sampling. The Kohn-Sham-gap (which is not equivalent to the 
lowest excitation energy of your system!) you obtain by subtracting the 
energy of the highest occupied VB-state from the energy of the lowest 
unoccupied CB-state. You typically obtain those in the non-self 
consistent calculation using k-points along the high symmetry paths of 
your Brillouin-zone.

Best regards,

Bálint




On 6/27/24 5:46 PM, Achyut Subedi wrote:
> Which one is more correct for the band gap? If I am reporting in bulk.
> Also the Fermi level -of my system-which is stored in 
> *detailed.out*,   files that comes after *DOS calculation* and *band 
> structure *calculation are different. Why is that? Which value of Fermi 
> level is correct? And which value of band_gap is more correct? The one 
> that we can calculate from *dos_total.dat *file or the one we get from 
> subtracting the maximum energy below Fermi level (or detailed.out that 
> comes after band_structure calculation) and minimum energy above Fermi 
> level ?
> 
> How can we match the band_gap calculated from DOS and band_structure?
> 
> Any help in this regard would be appreciated.
> 
> Thank you.
> -- 
> Best Regards
> Er. Achyut Subedi
> Registered Mechanical Engineer
> (IOE, TU, Nepal)
> +977-9847703110
> 
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-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.uni-bremen.de/en/lmcqm/b-aradi


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