Here we use the xc-field in Wannier basis to remove the spin polarization
from a spin polarized calculation.

This is a demonstration that the xc-field data work.

* The Fermi energy will be wrong of course.
* The little wiggles at the band bottom are due to inaccuracies
  if the Wannier model for the free electron bands.

You could compare to ../../NSP/slabify/3d
