  Perovskite transition-metal oxides are networks of corner-sharing octahedra
whose tilts and distortions are known to affect their electronic and magnetic
properties. We report calculations on a model interfacial structure to avoid
chemical influences and show that the symmetry mismatch imposes an interfacial
layer with distortion modes that do not exist in either bulk material, creating
new interface properties driven by symmetry alone. Depending on the resistance
of the octahedra to deformation, the interface layer can be as small as one
unit cell or extend deep into the thin film.
