Nb9V2O25 crystallizes in the tetragonal I4/m space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(5) and four O(6,6,6) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second Nb site, Nb(2) is bonded to one O(1), one O(3), one O(6), one O(7), and two equivalent O(2) atoms to form a mixture of edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 1-28°. In the third Nb site, Nb(3) is bonded to one O(2), one O(3), one O(4), one O(7), and two equivalent O(1) atoms to form distorted NbO6 octahedra that share corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Nb(3)O6 octahedra, corners with two equivalent V(1)O4 tetrahedra, and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 6-28°. V(1) is bonded to four equivalent O(4) atoms to form VO4 tetrahedra that share corners with four equivalent Nb(3)O6 octahedra and edges with two equivalent V(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 47°. There are nine inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one Nb(3) and two equivalent V(1) atoms. In the second O site, O(5) is bonded in a linear geometry to two equivalent Nb(1) atoms. In the third O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the fourth O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the fifth O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the sixth O site, O(7) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom. In the seventh O site, O(1) is bonded in a distorted T-shaped geometry to one Nb(2) and two equivalent Nb(3) atoms. In the eighth O site, O(2) is bonded in a distorted T-shaped geometry to one Nb(3) and two equivalent Nb(2) atoms. In the ninth O site, O(3) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom.
Nb9V2O25 crystallizes in the tetragonal I4/m space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(5) and four O(6,6,6) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Both Nb(1)-O(5) bond lengths are 2.00 Å. All Nb(1)-O(6,6,6) bond lengths are 2.06 Å. In the second Nb site, Nb(2) is bonded to one O(1), one O(3), one O(6), one O(7), and two equivalent O(2) atoms to form a mixture of edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 1-28°. The Nb(2)-O(1) bond length is 2.30 Å. The Nb(2)-O(3) bond length is 1.98 Å. The Nb(2)-O(6) bond length is 1.85 Å. The Nb(2)-O(7) bond length is 2.06 Å. Both Nb(2)-O(2) bond lengths are 2.06 Å. In the third Nb site, Nb(3) is bonded to one O(2), one O(3), one O(4), one O(7), and two equivalent O(1) atoms to form distorted NbO6 octahedra that share corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Nb(3)O6 octahedra, corners with two equivalent V(1)O4 tetrahedra, and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 6-28°. The Nb(3)-O(2) bond length is 2.29 Å. The Nb(3)-O(3) bond length is 1.89 Å. The Nb(3)-O(4) bond length is 2.14 Å. The Nb(3)-O(7) bond length is 1.87 Å. Both Nb(3)-O(1) bond lengths are 2.06 Å. V(1) is bonded to four equivalent O(4) atoms to form VO4 tetrahedra that share corners with four equivalent Nb(3)O6 octahedra and edges with two equivalent V(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 47°. All V(1)-O(4) bond lengths are 1.89 Å. There are nine inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one Nb(3) and two equivalent V(1) atoms. In the second O site, O(5) is bonded in a linear geometry to two equivalent Nb(1) atoms. In the third O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. In the fourth O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. The O(6)-Nb(2) bond length is 1.85 Å. In the fifth O site, O(6) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom. The O(6)-Nb(2) bond length is 1.85 Å. In the sixth O site, O(7) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom. In the seventh O site, O(1) is bonded in a distorted T-shaped geometry to one Nb(2) and two equivalent Nb(3) atoms. In the eighth O site, O(2) is bonded in a distorted T-shaped geometry to one Nb(3) and two equivalent Nb(2) atoms. In the ninth O site, O(3) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom.