[QE-users] About the Fermi level determination algorithm in q-e.

[Hongyi Zhao]

On Tue, Sep 15, 2020 at 3:56 PM Nicola Marzari <nicola.marzari at epfl.ch> wrote:
>
> On 15/09/2020 09:47, Hongyi Zhao wrote:
> > Hi,
> >
> > I try to figure out the Fermi level determination algorithm in q-e but
> > still not so clear on the procedure implemented currently.
> >
> > Any hints for this question?
> >
>
> bisection method

I searched the git local repo of q-e and find several results relevant
to 'bisection method':

q-e.git$ egrep -inR 'bisection method' .
./CPV/src/efermi.f90:147:!     chosen to be the robust bisection
method (from Numerical
./EPW/src/utilities.f90:603:    !! Energy of the current Fermi level
for the bisection method
./EPW/src/utilities.f90:605:    !! Energy lower bound for the bisection method
./EPW/src/utilities.f90:607:    !! Energy upper bound for the bisection method
./EPW/src/utilities.f90:709:      ! Use bisection method
./EPW/src/utilities.f90:777:      ! Use bisection method
./EPW/src/utilities.f90:827:      ! Use bisection method
./PW/src/efermig.f90:70:  ! ... Bisection method
./PW/src/efermit.f90:74:  !      Bisection method
./PW/src/tetra.f90:763:  !! Calculate Fermi energy by using bisection method.
./PW/src/tetra.f90:798:  ! Bisection method
./PP/simple_transport/src/ef.f90:140:         ! Compute efermi using
the bisection method

Are the algorithms appeared in these source code files exactly
equivalent or not? If they are exactly equivalent, why not create a
common function/library for this purpose?

Regards,
HY

>
> ----------------------------------------------------------------------
> Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
> Director, National Centre for Competence in Research NCCR MARVEL, EPFL
> http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project



-- 
Hongyi Zhao <hongyi.zhao at gmail.com>