BaNb7O9 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded to four equivalent O(4) and eight equivalent O(3) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with eight equivalent Nb(3)O5 square pyramids. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a square co-planar geometry to four equivalent O(1) atoms. In the second Nb site, Nb(2) is bonded in a square co-planar geometry to one O(1), one O(3), and two equivalent O(2) atoms. In the third Nb site, Nb(3) is bonded to one O(4) and four equivalent O(3) atoms to form NbO5 square pyramids that share corners with five equivalent Nb(3)O5 square pyramids and faces with four equivalent Ba(1)O12 cuboctahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a square co-planar geometry to two equivalent Nb(1) and two equivalent Nb(2) atoms. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to four equivalent Nb(2) atoms. In the third O site, O(3) is bonded to two equivalent Ba(1), one Nb(2), and two equivalent Nb(3) atoms to form a mixture of distorted edge and corner-sharing OBa2Nb3 trigonal bipyramids. In the fourth O site, O(4) is bonded in a distorted linear geometry to four equivalent Ba(1) and two equivalent Nb(3) atoms.
BaNb7O9 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded to four equivalent O(4) and eight equivalent O(3) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with eight equivalent Nb(3)O5 square pyramids. All Ba(1)-O(4) bond lengths are 2.99 Å. All Ba(1)-O(3) bond lengths are 2.92 Å. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a square co-planar geometry to four equivalent O(1) atoms. All Nb(1)-O(1) bond lengths are 2.12 Å. In the second Nb site, Nb(2) is bonded in a square co-planar geometry to one O(1), one O(3), and two equivalent O(2) atoms. The Nb(2)-O(1) bond length is 2.15 Å. The Nb(2)-O(3) bond length is 2.11 Å. Both Nb(2)-O(2) bond lengths are 2.12 Å. In the third Nb site, Nb(3) is bonded to one O(4) and four equivalent O(3) atoms to form NbO5 square pyramids that share corners with five equivalent Nb(3)O5 square pyramids and faces with four equivalent Ba(1)O12 cuboctahedra. The Nb(3)-O(4) bond length is 2.11 Å. All Nb(3)-O(3) bond lengths are 2.12 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a square co-planar geometry to two equivalent Nb(1) and two equivalent Nb(2) atoms. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to four equivalent Nb(2) atoms. In the third O site, O(3) is bonded to two equivalent Ba(1), one Nb(2), and two equivalent Nb(3) atoms to form a mixture of distorted edge and corner-sharing OBa2Nb3 trigonal bipyramids. In the fourth O site, O(4) is bonded in a distorted linear geometry to four equivalent Ba(1) and two equivalent Nb(3) atoms.