Materials Data on Sr2Nb5O9 by Materials Project
Sr2Nb5O9 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with eight equivalent SrO12 cuboctahedra, faces with five equivalent SrO12 cuboctahedra, faces with four equivalent NbO6 octahedra, and faces with four equivalent NbO5 square pyramids. There are a spread of Sr–O bond distances ranging from 2.81–2.97 Å. There are three inequivalent Nb+2.80+ sites. In the first Nb+2.80+ site, Nb+2.80+ is bonded to five O2- atoms to form NbO5 square pyramids that share a cornercorner with one NbO6 octahedra, corners with four equivalent NbO5 square pyramids, and faces with four equivalent SrO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Nb–O bond lengths are 2.11 Å. In the second Nb+2.80+ site, Nb+2.80+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.10 Å) and two longer (2.16 Å) Nb–O bond lengths. In the third Nb+2.80+ site, Nb+2.80+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with four equivalent NbO6 octahedra, corners with two equivalent NbO5 square pyramids, and faces with eight equivalent SrO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (1.97 Å) and four longer (2.10 Å) Nb–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a square co-planar geometry to four equivalent Nb+2.80+ atoms. In the second O2- site, O2- is bonded to two equivalent Sr2+ and three Nb+2.80+ atoms to form a mixture of distorted edge and corner-sharing OSr2Nb3 trigonal bipyramids. In the third O2- site, O2- is bonded in a distorted linear geometry to four equivalent Sr2+ and two Nb+2.80+ atoms. In the fourth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Sr2+ and two equivalent Nb+2.80+ atoms.