Atomistic study of surface polarization in superconducting perovskites

We simulated the surface relaxation of the cubic perovskite paraelectric SrTiO₃ crystal. The atomic positions in ten near-surface layers placed into the electrostatic field of the remainder of the crystal were calculated. Two-dimensional, periodic slab model was combined with the pair potentials treated in terms of the shell-model. Our calculations show that Ti⁺⁴, Sr⁺² and O^-2 ions shift differently from their crystal sites. This leads to a creation of a dipole moment near the surface which might give the paraelectric crystal the ferroelectric properties.