Materials Data on BaNb7O9 by Materials Project

Abstract

BaNb7O9 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with four equivalent BaO12 cuboctahedra, faces with four equivalent BaO12 cuboctahedra, and faces with eight equivalent NbO5 square pyramids. There are eight shorter (2.93 Å) and four longer (3.00 Å) Ba–O bond lengths. There are three inequivalent Nb+2.29+ sites. In the first Nb+2.29+ site, Nb+2.29+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Nb–O bond lengths are 2.12 Å. In the second Nb+2.29+ site, Nb+2.29+ is bonded in a square co-planar geometry to four O2- atoms. There are a spread of Nb–O bond distances ranging from 2.11–2.16 Å. In the third Nb+2.29+ site, Nb+2.29+ is bonded to five O2- atoms to form NbO5 square pyramids that share corners with five equivalent NbO5 square pyramids and faces with four equivalent BaO12 cuboctahedra. There are one shorter (2.12 Å) and four longer (2.13 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 Nb+2.29+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to four equivalent Nb+2.29+ atoms. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to two equivalent Ba2+ and three Nb+2.29+ atoms. In the fourth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+ and two equivalent Nb+2.29+ atoms.