[Pw_forum] Unit-cell and Super-cell bandgap difference

[dario rocca]

Dear Vipul,
There could be two main explanations for your results:
-A problem with the k-points you use  to compute the bandstrucure: the grid
for the cell and supercell must be consistent
-An error in the supercell. Try comparing total energies: does the
supercell have 8 times the total energy of the cell?
Best,
Dario Rocca

On Fri, Nov 25, 2016 at 7:47 AM, Vipul Shivaji Ghemud <
vipul at physics.unipune.ac.in> wrote:

> I have been using 8*8*8 for unit cell and 4*4*4 for supercell as my
> supercell is 2*2*2 unit cell.
>
> > Dear Vipul,
> > how many k-points did you use for the cell and for the supercell
> > Best
> > Dario
>
> > On Thu, Nov 24, 2016 at 6:23 AM, Vipul Shivaji Ghemud <
> > vipul at physics.unipune.ac.in> wrote:
>
> > Hi all,
> > I am working on a system of 9atoms in a unit-cell having bandgap of
> 3.5eV;
> > but I am considering the super-cell(4 unit-cells) then the bandgap is
> > reduced by ~0.45eV for HSE06. The bandgaps are similar with GGA. Is it
> due
> > to the exchnage-correlation contribution of the increased number of
> > electrons in the system, as the code QE considers unit-cell and
> super-cell
> > both a a single system? It's a bulk cubic system. I am facing similar
> > problem with other systems also.
> >
> >
> >
> > --
> > Vipul S. Ghemud
> > Ph.D. student.
> > Dept of Physics,
> > SPPU, Ganeshkhind,
> > Pune- 411007.
> >
> >
>
>
> --
> Vipul S. Ghemud
> Ph.D. student.
> Dept of Physics,
> SPPU, Ganeshkhind,
> Pune- 411007.
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20161125/dbd57155/attachment.html>