First-principles simulations on the structural and energetic properties of domains in PbTiO${}_3$/SrTiO${}_3$ superlattices

Abstract

We report first-principles calculations, within the density functional theory, on the structural and energetic properties of 180${}^{\circ }$ stripe domains in (PbTiO${}_3$)${}_n$/(SrTiO${}_3$)${}_n$ superlattices. For the explored periodicities ($n$=3 and 6) we find that the polydomain structures compete in energy with the monodomain phases. Our results suggest the progressive transition, as a function of $n$, from a strong to a weak electrostatic coupling regime between the SrTiO${}_3$ and PbTiO${}_3$ layers. Structurally, they display continuous rotation of polarization connecting 180${}^{\circ }$ domains. A large offset between [100] atomic rows across the domain wall and huge strain gradients are observed. The domain wall energy is very isotropic, depending very weakly on the stripe orientation.

8 pages, 7 figures