Structure and energetics of 180° domain walls in PbTiO₃ by density functional theory

Density functional theory at the level of the local density approximation with the projector augmented wave method is used to determine the structure of 180° domain walls in tetragonal ferroelectric PbTiO₃. In agreement with previous studies, it is found that PbO-centered {100} walls have lower energies than TiO₂-centered {100} walls, leading to a Peierls potential barrier for wall motion along 〈010〉 of ∼ 36mJm ^-2. In addition to the Ising-like polarization along the tetragonal axis, it is found that near the domain wall, there is a small polarization in the wall-normal direction away from the domain wall. These Néel-like contributions to the domain wall are analyzed in terms of the Landau-Ginzburg-Devonshire phenomenological theory for ferroelectrics. Similar characteristics are found for {110} domain walls, where OO-centered walls are energetically more favorable than the PbTiO-centered walls.