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

[Vipul Shivaji Ghemud]

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.