[Pw_forum] Shifting Fermi energy for Fermi surface calculations and X-mas

[Eyvaz Isaev]

Hi,

>That code requires in input the Fermi energy (it  might
>read it from the bands data, but apparently it doesn't).

Well, it is my pleasure telling you that I will fix this small problem soon.  

By the way, why we are discussing such kind serious problems, when X-mas is approaching? 
Merry X-mas and Happy New Year to all q-ESPRESSO Developers and Users!

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


--- On Wed, 12/23/09, Paolo Giannozzi <giannozz at democritos.it> wrote:

> From: Paolo Giannozzi <giannozz at democritos.it>
> Subject: Re: [Pw_forum] Shifting Fermi energy for Fermi surface calculations
> To: "PWSCF Forum" <pw_forum at pwscf.org>
> Date: Wednesday, December 23, 2009, 11:09 PM
> 
> On Dec 23, 2009, at 20:52 , Nicki Frank Hinsche wrote:
> 
> > 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.
> 
> input_FS is the file containing input data for the program

> (written  by Eyvaz)

> that calculates the Fermi surface, given the band
> structure calculated in a  previous run, IIRC. That code requires in input the Fermi energy (it  might
> read it from the bands data, but apparently it doesn't). If
> this is  your problem: you can change the Fermi at will, since the band structure is fixed.
> 
> You can change the Fermi energy in a self-consistent way by
> adding or  removing charge to the system (variable "nelec"). This will 
> modify the band structure wrt the  neutral case, but not by much if you add or remove just a  fraction of an electron.  The code will take care of adding a neutralizing background (needed in order to have a finite value of the energy).
> 
> Paolo
> ---
> Paolo Giannozzi, Dept of Physics, University of Udine
> via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>