Ferrielectric twin walls in CaTiO3

Sizeable spontaneous polarization has been found in the (100) twin walls of CaTiO3, a definitely nonpolar material. Theoretical simulations of these walls show an extremely rich texture of the local polarization at and close to the walls, including a strong anti ferroelectric component, and local nonzero contributions perpendicular to the wall plane, which do not contribute to the net dipole. Individual Ti displacements of 2 pin off the octahedron center give rise to a net polarization corresponding to a displacement of 0.6 pm in the direction of the bisector of the twin angle.