But I mentioned a problem with using a very dense k - point grid and an 8 atom Si cell, the program exits before it can output the forces, stresses, and the individual contributions to the total energy (hence why regardless of what screening parameter I used I got the same band gap, as the fock). Nobody was able to point me in the right direction with that. Also, another user has previously reported that using a 2 atom si cell results in an oscillation in the total energy as you increase ecutwfc (something I have also verified), so I'm not sure I can accurately calculate the band gap using a 2 atom cell either.
Phil On 11 November 2015 at 12:18, Ref Fymz <[email protected]> wrote: > Hey, > > Thanks for the reply. So if I use an 8 atom Si cell, and use fixed > occupations with 32 bands, the difference between the highest occupied and > lowest unoccupied is my actual band gap? (i.e the one I can compare to PBE > and experiment) > > > Phil > > On 11 November 2015 at 10:13, Ref Fymz <[email protected]> wrote: > >> Hey, >> >> I've tried searching the forum, and I haven't come across a way to >> calculate the band gap in a material using the hybrid functionals. I know >> you can't do nscf calculations, but is there any simple way to calculate >> the band gap for a material using scf simulations? >> >> Thanks, >> >> Phil >> > >
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