AlNbO4 crystallizes in the monoclinic Cm space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(3), one O(8), and two equivalent O(5) atoms. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(10), one O(15), one O(7), one O(9), and two equivalent O(13) atoms. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(15), one O(4), and two equivalent O(2) atoms. In the fourth Nb site, Nb(4) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(16), one O(6), and two equivalent O(14) atoms. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(11), one O(5), one O(6), and two equivalent O(3) atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 26°. In the second Al site, Al(2) is bonded to one O(13), one O(16), one O(2), one O(7), and two equivalent O(15) atoms to form a mixture of distorted corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 29°. In the third Al site, Al(3) is bonded to one O(10), one O(2), one O(7), one O(8), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 26°. In the fourth Al site, Al(4) is bonded to one O(14), one O(5), one O(6), one O(9), and two equivalent O(12) atoms to form a mixture of distorted corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 29°. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Nb(3) and one Al(1) atom. In the second O site, O(2) is bonded to two equivalent Nb(3), one Al(2), and one Al(3) atom to form corner-sharing ONb2Al2 trigonal pyramids. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Nb(1) and two equivalent Al(1) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Nb(3) and two equivalent Al(3) atoms. In the fifth O site, O(5) is bonded to two equivalent Nb(1), one Al(1), and one Al(4) atom to form corner-sharing ONb2Al2 trigonal pyramids. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Nb(4), one Al(1), and one Al(4) atom. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Nb(2), one Al(2), and one Al(3) atom. In the eighth O site, O(8) is bonded in a linear geometry to one Nb(1) and one Al(3) atom. In the ninth O site, O(9) is bonded in a linear geometry to one Nb(2) and one Al(4) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(3), and one Al(3) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(4), and one Al(1) atom. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to one Nb(1), one Nb(4), and two equivalent Al(4) atoms. In the thirteenth O site, O(13) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Nb(2) and one Al(2) atom. In the fourteenth O site, O(14) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Nb(4) and one Al(4) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Nb(2), one Nb(3), and two equivalent Al(2) atoms. In the sixteenth O site, O(16) is bonded in a linear geometry to one Nb(4) and one Al(2) atom.
AlNbO4 crystallizes in the monoclinic Cm space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(3), one O(8), and two equivalent O(5) atoms. The Nb(1)-O(11) bond length is 1.88 Å. The Nb(1)-O(12) bond length is 2.47 Å. The Nb(1)-O(3) bond length is 2.04 Å. The Nb(1)-O(8) bond length is 1.82 Å. Both Nb(1)-O(5) bond lengths are 2.03 Å. In the second Nb site, Nb(2) is bonded in a 6-coordinate geometry to one O(10), one O(15), one O(7), one O(9), and two equivalent O(13) atoms. The Nb(2)-O(10) bond length is 2.31 Å. The Nb(2)-O(15) bond length is 2.11 Å. The Nb(2)-O(7) bond length is 2.00 Å. The Nb(2)-O(9) bond length is 1.83 Å. Both Nb(2)-O(13) bond lengths are 1.99 Å. In the third Nb site, Nb(3) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(15), one O(4), and two equivalent O(2) atoms. The Nb(3)-O(1) bond length is 1.80 Å. The Nb(3)-O(10) bond length is 1.88 Å. The Nb(3)-O(15) bond length is 2.47 Å. The Nb(3)-O(4) bond length is 2.04 Å. Both Nb(3)-O(2) bond lengths are 2.03 Å. In the fourth Nb site, Nb(4) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(16), one O(6), and two equivalent O(14) atoms. The Nb(4)-O(11) bond length is 2.31 Å. The Nb(4)-O(12) bond length is 2.11 Å. The Nb(4)-O(16) bond length is 1.83 Å. The Nb(4)-O(6) bond length is 2.00 Å. Both Nb(4)-O(14) bond lengths are 1.99 Å. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(11), one O(5), one O(6), and two equivalent O(3) atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 26°. The Al(1)-O(1) bond length is 1.87 Å. The Al(1)-O(11) bond length is 1.91 Å. The Al(1)-O(5) bond length is 2.00 Å. The Al(1)-O(6) bond length is 1.97 Å. Both Al(1)-O(3) bond lengths are 1.95 Å. In the second Al site, Al(2) is bonded to one O(13), one O(16), one O(2), one O(7), and two equivalent O(15) atoms to form a mixture of distorted corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 29°. The Al(2)-O(13) bond length is 1.93 Å. The Al(2)-O(16) bond length is 1.83 Å. The Al(2)-O(2) bond length is 2.15 Å. The Al(2)-O(7) bond length is 1.80 Å. Both Al(2)-O(15) bond lengths are 1.96 Å. In the third Al site, Al(3) is bonded to one O(10), one O(2), one O(7), one O(8), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 26°. The Al(3)-O(10) bond length is 1.91 Å. The Al(3)-O(2) bond length is 2.00 Å. The Al(3)-O(7) bond length is 1.97 Å. The Al(3)-O(8) bond length is 1.88 Å. Both Al(3)-O(4) bond lengths are 1.95 Å. In the fourth Al site, Al(4) is bonded to one O(14), one O(5), one O(6), one O(9), and two equivalent O(12) atoms to form a mixture of distorted corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 29°. The Al(4)-O(14) bond length is 1.93 Å. The Al(4)-O(5) bond length is 2.15 Å. The Al(4)-O(6) bond length is 1.80 Å. The Al(4)-O(9) bond length is 1.83 Å. Both Al(4)-O(12) bond lengths are 1.96 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Nb(3) and one Al(1) atom. In the second O site, O(2) is bonded to two equivalent Nb(3), one Al(2), and one Al(3) atom to form corner-sharing ONb2Al2 trigonal pyramids. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Nb(1) and two equivalent Al(1) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to one Nb(3) and two equivalent Al(3) atoms. In the fifth O site, O(5) is bonded to two equivalent Nb(1), one Al(1), and one Al(4) atom to form corner-sharing ONb2Al2 trigonal pyramids. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Nb(4), one Al(1), and one Al(4) atom. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Nb(2), one Al(2), and one Al(3) atom. In the eighth O site, O(8) is bonded in a linear geometry to one Nb(1) and one Al(3) atom. In the ninth O site, O(9) is bonded in a linear geometry to one Nb(2) and one Al(4) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Nb(2), one Nb(3), and one Al(3) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Nb(1), one Nb(4), and one Al(1) atom. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to one Nb(1), one Nb(4), and two equivalent Al(4) atoms. In the thirteenth O site, O(13) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Nb(2) and one Al(2) atom. In the fourteenth O site, O(14) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Nb(4) and one Al(4) atom. In the fifteenth O site, O(15) is bonded in a 4-coordinate geometry to one Nb(2), one Nb(3), and two equivalent Al(2) atoms. In the sixteenth O site, O(16) is bonded in a linear geometry to one Nb(4) and one Al(2) atom.