Epitaxially strained [001]-(PbTiO3)1(PbZrO3)1 superlattice and PbTiO3 from first principles -: art. no. 184101

The effect of layer-by-layer heterostructuring and epitaxial strain on lattice instabilities and related ferroelectric properties is investigated from first principles for the [001]-(PbTiO3)(1)(PbZrO3)(1) superlattice and pure PbTiO3 on a cubic substrate. The results for the superlattice show an enhancement of the stability of the monoclinic r phase with respect to pure PbTiO3. Analysis of the lattice instabilities of the relaxed centrosymmetric reference structure computed within density functional perturbation theory suggests that this results from the presence of two unstable zone-center modes, one confined in the PbTiO3 layer and one in the PbZrO3 layer, which produce in-plane and normal components of the polarization, respectively. The zero-temperature dielectric response is computed and shown to be enhanced not only near the phase boundaries, but throughout the r phase. Analysis of the analogous calculation for pure PbTiO3 is consistent with this interpretation, and suggests useful approaches to engineering the dielectric properties of artificially structured perovskite oxides.