[Wien] Bandgap of ionic bonds

[Stefaan Cottenier]

> I once heard that other types are also available as hidden options.

See http://zeus.theochem.tuwien.ac.at/pipermail/wien/2003-June/000090.html

>  One more complicataion; if I increase the R*Kmax value to 8 or higher, 
> the bandgap
>  disappears.

Then the true LDA/GGA result is that there is no bandgap. You should at 
least determine for which Rkmax your result doesn't change anymore on 
further increasing RKmax (check the fermi energy, for instance). It doesn't 
make sense to stick to a smaller RKmax just because there there is still a 
band gap: such a calculation is unreliable.

Stefaan