In this thesis SrRuO3 /PbTiO3 superlattices are studied. Experimentally it is not known which interface forms when these structures are grown. We investigated the formation energy, the structural, electrostatic, magnetic and electronic properties of the different interfaces and compared our findings to measurements to determine the interface structure realized in experiments. The dependence of the superlattices on strain and rotational distortions is also analyzed. For asymmetric interface structures we find an interesting phase diagram of the superlattices going from a ferroelectric material with an asymmetric double-well potential then via a self-poling polar structure to a paraelectric superlattice when the PbTiO3 volume fraction is decreased.