[Pw_forum] band gap at Gamma point in primitive cell different from the band gap at Gamma point in conventional cell

[Juliana Morbec]

Dear All.

I have tried to calculate the band gap of Ta3N5. When I use the primitive
cell with 16 atoms I obtain a band gap of 1.68 eV at the Gamma point;
however, when I use the conventional cell with 32 atoms, I find a band gap
 of 1.34 eV at the Gamma point. I have already checked the convergence of
both calculations with respect to the energy cutoff and the k-point grid.

I was wondering if this could be related to the Brillouin zone folding. Do
anyone have any idea why I obtain too different values at the same point?

I will really appreciate any help in this issue.

Best wishes,

Juliana Morbec
-----
Juliana M. Morbec, Ph.D.
Postdoctoral Researcher
Institute for Molecular Engineering, The University of Chicago
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