[DFTB-Plus-User] Fermi level in DOS and Band calculation

[R.Perez Garcia]

(Dear DFTB users),
Dear Prof. Aradi,
Thank you for your detailed answers.
Reading Prof. Aradi answer two more question arise to me. First, in order to calculate the DOS at temperatures higher than 0K what shall I do? I thought it can not be done... 
Second, and less important, for the Valence Band edge...I normally count the electrons and check the correlative orbital, is there any other mean of doing this?
Thank you again for your time and consideration.
Best regards, R

On 28-08-12, Bálint Aradi  <balint.aradi at bccms.uni-bremen.de> wrote:
> Dear R,
> 
> > I have a doubt regarding the Fermi Energy.
> > It differ in the DOS calculation and in the subsequent calculation for
> > the Band Structure. Which is more likely to be correct in your opinion?
> > Please let me know if you need any further data.
> > Best regards: R
> 
>  The position of the Fermi energy heavily depends on your sampling of
> the Brillouin-zone. Usually, for DOS calculation you choose a proper
> sampling, while for band structure you sample along high symmetry lines.
> So in the former case it should be more accurate.
> 
>   Please note, however, that due to numerical issues, in case of
> isolators the position of the Fermi level is somewhat arbitrary between
> the highest occupied and the lowest unoccupied state. At 0K it should be
> theoretically in the middle between them, and by raising temperature
> move depending on the density of states at the band edges. But at lower
> temperatures and big gaps it is hard to find that position numerically.
> If you need a practical reference in those cases, take the VB edge.
> 
>  Best regards,
> 
>    Bálint
> 
> -- 
> Dr. Bálint Aradi
> Bremen Center for Computational Materials Science, University of Bremen
> http://www.bccms.uni-bremen.de/cms/people/b_aradi/
> 
> 
> 
> 
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