  The role of electronic correlation effects for a realistic description of the
electronic properties of LaAlO3/SrTiO3 heterostructures as covered by the
on-site Coulomb repulsion within the GGA+U approach is investigated. Performing
a systematic variation of the values of the Coulomb parameters applied to the
Ti 3d and La 4f orbitals we put previous suggestions to include a large value
for the La 4f states into perspective. Furthermore, our calculations provide
deeper insight into the band gap landscape in the space spanned by these
Coulomb parameters and the resulting complex interference effects. In addition,
we identify important correlations between the local Coulomb interaction within
the La 4f shell, the band gap, and the atomic displacements at the interface.
In particular, these on-site Coulomb interactions influence buckling within the
LaO interface layer, which via its strong coupling to the electrostatic
potential in the LAO overlayer causes considerable shifts of the electronic
states at the surface and eventually controls the band gap.
