Materials Data on Sr3Ti2O7 by Materials Project
Sr3Ti2O7 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.50–2.79 Å. In the second Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with four equivalent SrO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, and faces with eight equivalent TiO6 octahedra. All Sr–O bond lengths are 2.79 Å. Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with five equivalent TiO6 octahedra and faces with four equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–2°. There is five shorter (1.97 Å) and one longer (2.01 Å) Ti–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to four Sr2+ and two equivalent Ti4+ atoms. In the second O2- site, O2- is bonded to five equivalent Sr2+ and one Ti4+ atom to form a mixture of distorted edge and corner-sharing OSr5Ti octahedra. The corner-sharing octahedral tilt angles are 8°. In the third O2- site, O2- is bonded in a distorted linear geometry to four equivalent Sr2+ and two equivalent Ti4+ atoms.