[Pw_forum] Shifting Fermi energy for Fermi surface calculations

[Nicki Frank Hinsche]

Dear Eyvaz,

You are right. I already mentioned this in my first post. In the right  
physical way I want to simulate doping by shifting the chemical  
potential to an energy near the original Fermi energy for the charge  
neutral, isolating system.
In any case the chemical potential has to be shifted in either  
valence- or conduction band and therefore there would be an iso-energy  
surface (what I sloppy called Fermi surface...).

in any case, thank you

Nicki

> Dear Nicki,
>
>> I just want to know whether and how it is possible to shift
>> the Fermi  energy before constructing the Fermi surface?!
>
>> I just want to know whether and how it is possible to shift
>> the Fermi  energy before constructing the Fermi surface?!
>
> I should note there is NO Fermi level, thus, no Fermi surface for  
> semiconductors!!! Please think about why.
>
> Bests,
> Eyvaz.
>
> -------------------------------------------------------------------
> Prof. Eyvaz Isaev,
> Theoretical Physics Department, Moscow State Institute of Steel &  
> Alloys, Russia,
> Department of Physics, Chemistry, and Biology (IFM), Linkoping  
> University, Sweden
> Condensed Matter Theory Group, Uppsala University, Sweden
> Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com

Dear Paolo,

The previous stages are the formal ones:

-making a proper scf calculation for the isolating system
-calculate the total DOS to obtain the size of the gap and the  
possible energetic positions of valence/conduction band edge, where  
later on the chemical potential should be shifted into.
-generating a k-point grid in the BZ with kvecs_FS.x
-afterwards the eigenvalues are calculated on this grid for one  
special energy -> this is the Fermi energy, but:

For my isolating system the Fermi energy would be in the gap,  
therefore there wont be an eigenvalue for given k-points at the Fermi  
energy. If I shift the energy to a value right where states are, then  
I would expect of course some contribution to an iso-energetic  
surface. But how to change this 'Fermi energy' in the right way. Is it  
enough to change the parameter in input_FS? Of course I know, that the  
system isn't charge-neutral anymore after artificially shifting the  
Fermi energy.

Thanks a lot,

Nicki


> On Dec 23, 2009, at 14:32 , Nicki Frank Hinsche wrote:
>
>> plotting the fermi surface for the shifted energy would be the last
>> stage...
>
> and what are the previous stages? P.
> ---
> Paolo Giannozzi, Dept of Physics, University of Udine
> via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222

-------------------------------------------------------------
Nicki Frank Hinsche, Dipl. Phys.
Institut für Physik - Theoretische Physik,
Martin-Luther-Universität Halle-Wittenberg,
Von-Seckendorff-Platz 1, Raum 1.07
D-06120 Halle/Saale, Germany
Tel.: ++49 345 5525460
nicki.hinsche at physik.uni-halle.de
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