[Wien] Supercell Coulomb potential using single unitcell results

[Marco Schowalter]

Dear Changlin Zheng,

I think the second method you mention will not work, since the MIP
depends on the type of surface. The charge distribution of the surface
will change the Coulomb potential in the vacuum and hence the zero point
of the Coulomb potential (See for example the paper of Kim et al.). In
order to get the charge distribution at the surface correct it is not
sufficient to compute a thin slab only. Since the MIP is a property of
the bulk crystal you have to check convergence with respect to the
thickness of the slab.