Bandstructure of GaN

[kesh]

Hi!
I am trying to simulate the bandstructure of GaN and I know it has a direct band gap of about 3.4eV but the results I'm getting from the simulation shows an indirect band gap. Do I need to do something extra before simulating it?

Thanks

[Nordland]

Are you doing a DFT-LDA calculation?

[kesh]

Yes I am doing a DFT-LDA calculation

[Nordland]

So if your question goes to why the band gap is not the correct value, I have this link http://www.iop.kiev.ua/~yakovkin/My_pdf/Exchange_gap.pdf for you. It is more or less - a fundamental properties that
the band gap is not well described in LDA. There are method for compensate for this like LDA+U or MGGA, but it is an intrinsic property of LDA that it gives too small band gaps.

[kesh]

Thank you!