Credit:
The atomic scale structure of a 1/1 PbTiO3/SrTiO3 superlattice (as obtained from first-principles calculations), (Pb atoms in grey, Sr atoms in blue, Ti atoms in green and O atoms in red). The associated electron cloud is in yellow. The distinct rotations of oxygen atoms (in red) in consecutive layers are generated by the artificially produced layering in the structure and are a specific feature of the improper ferroelectric behavior discovered. (© University of Liège)