[Pw_forum] Shifting Fermi energy for Fermi surface calculations and X-mas
Eyvaz Isaev
eyvaz_isaev at yahoo.com
Wed Dec 23 22:17:24 CET 2009
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
>
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