  Total energies, electronic structure, surface energies, polarization,
potentials and charge densities were studied for slabs of BaTiO_3 using the
Linearized Augmented Plane Wave (LAPW) method. The depolarization field
inhibits ferroelectricity in the slabs, and the macroscopic field set up across
a ferroelectric slab is sufficient to cause electronic states to span the gap
and give a metallic band structure, but the band shifts are not rigid and O p
states tend to pile up at the Fermi level. There are electronic surface states,
especially evident on TiO_2 surfaces. The dangling bonds bond back to the
surface Ti's and make the surface stable and reactive. The BaO surfaces are
more ionic than the bulk.
