Figure 1 : The atomic structures of (a) the unrelaxed and (b) relaxed TiO2 terminated tetragonal SrTiO3 slab.

From: Oxygen Vacancy Induced Flat Phonon Mode at FeSe /SrTiO3 interface

Figure 1

The black arrows indicated the antiferrodistortive rotation in tetragonal phase SrTiO3 below 105 K, and the interlayer Ti-O bond length in top three layers are denoted.