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

[Vipul Shivaji Ghemud]

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.