[Wien] vacuum states in graphene slab calculations

[katrusiat]

Dear Wien2k community,

I perform slab calculations for the graphene single layers separated by ~ 10 A of vacuum.
In the bandstructure that comes out one sees a dense bunch of bands ~ 3 eV above the Fermi level which have parabolic behavior at the Gamma point.
Supposedly, these bands are the plane-wave states which describe the vast interstitial region.

My question is the following: If this interpretation of the dense bands above the Fermi level as plane-wave states is correct,
then these bands should be considered as artifacts of the Wien2k basis set. Can one get rid of them somehow?

Thanks!
Kateryna Foyevtsova