Nb12O29 crystallizes in the monoclinic C2/m space group. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(2), one O(7), two equivalent O(4), and two equivalent O(6) atoms. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(8), and two equivalent O(2) atoms. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one O(2), one O(5), one O(6), one O(9), and two equivalent O(3) atoms. In the fourth Nb site, Nb(4) is bonded to one O(10), one O(11), one O(15), one O(7), and two equivalent O(13) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 4-32°. In the fifth Nb site, Nb(5) is bonded to one O(13), one O(14), one O(15), one O(8), and two equivalent O(11) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 5-32°. In the sixth Nb site, Nb(6) is bonded to one O(1), one O(10), one O(14), one O(9), and two equivalent O(12) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-15°. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Nb(6) atoms. In the second O site, O(2) is bonded to one Nb(1), one Nb(3), and two equivalent Nb(2) atoms to form distorted corner-sharing ONb4 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(3) atoms. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Nb(3) and two equivalent Nb(1) atoms. In the seventh O site, O(7) is bonded in a linear geometry to one Nb(1) and one Nb(4) atom. In the eighth O site, O(8) is bonded in a linear geometry to one Nb(2) and one Nb(5) atom. In the ninth O site, O(9) is bonded in a linear geometry to one Nb(3) and one Nb(6) atom. In the tenth O site, O(10) is bonded in a linear geometry to one Nb(4) and one Nb(6) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Nb(4) and two equivalent Nb(5) atoms. In the twelfth O site, O(12) is bonded in a linear geometry to two equivalent Nb(6) atoms. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one Nb(5) and two equivalent Nb(4) atoms. In the fourteenth O site, O(14) is bonded in a linear geometry to one Nb(5) and one Nb(6) atom. In the fifteenth O site, O(15) is bonded in a linear geometry to one Nb(4) and one Nb(5) atom.
Nb12O29 crystallizes in the monoclinic C2/m space group. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(2), one O(7), two equivalent O(4), and two equivalent O(6) atoms. The Nb(1)-O(2) bond length is 2.31 Å. The Nb(1)-O(7) bond length is 1.80 Å. Both Nb(1)-O(4) bond lengths are 2.01 Å. There is one shorter (1.91 Å) and one longer (2.44 Å) Nb(1)-O(6) bond length. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(8), and two equivalent O(2) atoms. The Nb(2)-O(3) bond length is 2.35 Å. The Nb(2)-O(4) bond length is 2.28 Å. The Nb(2)-O(5) bond length is 1.87 Å. The Nb(2)-O(8) bond length is 1.81 Å. Both Nb(2)-O(2) bond lengths are 2.04 Å. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one O(2), one O(5), one O(6), one O(9), and two equivalent O(3) atoms. The Nb(3)-O(2) bond length is 2.48 Å. The Nb(3)-O(5) bond length is 2.02 Å. The Nb(3)-O(6) bond length is 2.15 Å. The Nb(3)-O(9) bond length is 1.78 Å. Both Nb(3)-O(3) bond lengths are 2.02 Å. In the fourth Nb site, Nb(4) is bonded to one O(10), one O(11), one O(15), one O(7), and two equivalent O(13) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 4-32°. The Nb(4)-O(10) bond length is 1.84 Å. The Nb(4)-O(11) bond length is 2.29 Å. The Nb(4)-O(15) bond length is 1.92 Å. The Nb(4)-O(7) bond length is 2.17 Å. Both Nb(4)-O(13) bond lengths are 2.01 Å. In the fifth Nb site, Nb(5) is bonded to one O(13), one O(14), one O(15), one O(8), and two equivalent O(11) atoms to form a mixture of distorted corner and edge-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 5-32°. The Nb(5)-O(13) bond length is 2.29 Å. The Nb(5)-O(14) bond length is 1.85 Å. The Nb(5)-O(15) bond length is 1.94 Å. The Nb(5)-O(8) bond length is 2.14 Å. Both Nb(5)-O(11) bond lengths are 2.01 Å. In the sixth Nb site, Nb(6) is bonded to one O(1), one O(10), one O(14), one O(9), and two equivalent O(12) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 0-15°. The Nb(6)-O(1) bond length is 1.94 Å. The Nb(6)-O(10) bond length is 2.03 Å. The Nb(6)-O(14) bond length is 2.04 Å. The Nb(6)-O(9) bond length is 2.23 Å. Both Nb(6)-O(12) bond lengths are 1.95 Å. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Nb(6) atoms. In the second O site, O(2) is bonded to one Nb(1), one Nb(3), and two equivalent Nb(2) atoms to form distorted corner-sharing ONb4 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(3) atoms. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Nb(3) and two equivalent Nb(1) atoms. In the seventh O site, O(7) is bonded in a linear geometry to one Nb(1) and one Nb(4) atom. In the eighth O site, O(8) is bonded in a linear geometry to one Nb(2) and one Nb(5) atom. In the ninth O site, O(9) is bonded in a linear geometry to one Nb(3) and one Nb(6) atom. In the tenth O site, O(10) is bonded in a linear geometry to one Nb(4) and one Nb(6) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Nb(4) and two equivalent Nb(5) atoms. In the twelfth O site, O(12) is bonded in a linear geometry to two equivalent Nb(6) atoms. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one Nb(5) and two equivalent Nb(4) atoms. In the fourteenth O site, O(14) is bonded in a linear geometry to one Nb(5) and one Nb(6) atom. In the fifteenth O site, O(15) is bonded in a linear geometry to one Nb(4) and one Nb(5) atom.