Materials Data on Ba3SrNb2O9 by Materials Project
Ba3SrNb2O9 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with six equivalent BaO12 cuboctahedra, faces with two equivalent SrO6 octahedra, and faces with six equivalent NbO6 octahedra. There are six shorter (3.00 Å) and six longer (3.05 Å) Ba–O bond lengths. In the second Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are three shorter (2.76 Å) and six longer (3.08 Å) Ba–O bond lengths. Sr2+ is bonded to six equivalent O2- atoms to form SrO6 octahedra that share corners with six equivalent NbO6 octahedra and faces with two equivalent BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 15°. All Sr–O bond lengths are 2.46 Å. Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with three equivalent SrO6 octahedra, faces with three equivalent BaO12 cuboctahedra, and a faceface with one NbO6 octahedra. The corner-sharing octahedral tilt angles are 15°. There are three shorter (1.91 Å) and three longer (2.20 Å) Nb–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to four Ba2+ and two equivalent Nb5+ atoms to form a mixture of distorted face and corner-sharing OBa4Nb2 octahedra. The corner-sharing octahedra tilt angles range from 6–60°. In the second O2- site, O2- is bonded in a 2-coordinate geometry to three Ba2+, one Sr2+, and one Nb5+ atom.