UNb6O16 crystallizes in the triclinic P1 space group. U(1) is bonded to one O(1), one O(14), one O(15), one O(2), one O(8), and one O(9) atom to form UO6 octahedra that share  a cornercorner with one Nb(6)O6 octahedra and  an edgeedge with one Nb(6)O6 octahedra. The corner-sharing octahedral tilt angles are 32°. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(15), one O(2), and one O(3) atom. In the second Nb site, Nb(2) is bonded to one O(12), one O(16), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NbO6 octahedra that share  a cornercorner with one Nb(6)O6 octahedra,  a cornercorner with one Nb(5)O5 trigonal bipyramid, and  an edgeedge with one Nb(5)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 45°. In the third Nb site, Nb(3) is bonded in a 5-coordinate geometry to one O(11), one O(5), one O(6), one O(7), and one O(8) atom. In the fourth Nb site, Nb(4) is bonded in a 4-coordinate geometry to one O(10), one O(11), one O(6), and one O(9) atom. In the fifth Nb site, Nb(5) is bonded to one O(11), one O(12), one O(13), one O(16), and one O(4) atom to form a mixture of corner and edge-sharing NbO5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 2-42°. In the sixth Nb site, Nb(6) is bonded to one O(1), one O(10), one O(13), one O(14), one O(15), and one O(5) atom to form distorted NbO6 octahedra that share  a cornercorner with one U(1)O6 octahedra,  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(5)O5 trigonal bipyramid, and  an edgeedge with one U(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-45°. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to one U(1), one Nb(1), and one Nb(6) atom. In the second O site, O(2) is bonded in a water-like geometry to one U(1) and one Nb(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(2) atom. In the fourth O site, O(4) is bonded in a linear geometry to one Nb(2) and one Nb(5) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Nb(2), one Nb(3), and one Nb(6) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Nb(2), one Nb(3), and one Nb(4) atom. In the seventh O site, O(7) is bonded in a single-bond geometry to one Nb(3) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one U(1) and one Nb(3) atom. In the ninth O site, O(9) is bonded in a bent 120 degrees geometry to one U(1) and one Nb(4) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Nb(4) and one Nb(6) atom. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Nb(3), one Nb(4), and one Nb(5) atom. In the twelfth O site, O(12) is bonded in a water-like geometry to one Nb(2) and one Nb(5) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Nb(5) and one Nb(6) atom. In the fourteenth O site, O(14) is bonded in a water-like geometry to one U(1) and one Nb(6) atom. In the fifteenth O site, O(15) is bonded in a distorted T-shaped geometry to one U(1), one Nb(1), and one Nb(6) atom. In the sixteenth O site, O(16) is bonded in a water-like geometry to one Nb(2) and one Nb(5) atom.
UNb6O16 crystallizes in the triclinic P1 space group. U(1) is bonded to one O(1), one O(14), one O(15), one O(2), one O(8), and one O(9) atom to form UO6 octahedra that share  a cornercorner with one Nb(6)O6 octahedra and  an edgeedge with one Nb(6)O6 octahedra. The corner-sharing octahedral tilt angles are 32°. The U(1)-O(1) bond length is 2.23 Å. The U(1)-O(14) bond length is 2.16 Å. The U(1)-O(15) bond length is 2.25 Å. The U(1)-O(2) bond length is 2.16 Å. The U(1)-O(8) bond length is 2.14 Å. The U(1)-O(9) bond length is 2.19 Å. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(15), one O(2), and one O(3) atom. The Nb(1)-O(1) bond length is 2.06 Å. The Nb(1)-O(15) bond length is 2.05 Å. The Nb(1)-O(2) bond length is 1.91 Å. The Nb(1)-O(3) bond length is 1.94 Å. In the second Nb site, Nb(2) is bonded to one O(12), one O(16), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NbO6 octahedra that share  a cornercorner with one Nb(6)O6 octahedra,  a cornercorner with one Nb(5)O5 trigonal bipyramid, and  an edgeedge with one Nb(5)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 45°. The Nb(2)-O(12) bond length is 2.29 Å. The Nb(2)-O(16) bond length is 1.85 Å. The Nb(2)-O(3) bond length is 1.93 Å. The Nb(2)-O(4) bond length is 1.94 Å. The Nb(2)-O(5) bond length is 2.33 Å. The Nb(2)-O(6) bond length is 2.14 Å. In the third Nb site, Nb(3) is bonded in a 5-coordinate geometry to one O(11), one O(5), one O(6), one O(7), and one O(8) atom. The Nb(3)-O(11) bond length is 2.13 Å. The Nb(3)-O(5) bond length is 2.01 Å. The Nb(3)-O(6) bond length is 2.14 Å. The Nb(3)-O(7) bond length is 1.75 Å. The Nb(3)-O(8) bond length is 1.92 Å. In the fourth Nb site, Nb(4) is bonded in a 4-coordinate geometry to one O(10), one O(11), one O(6), and one O(9) atom. The Nb(4)-O(10) bond length is 1.86 Å. The Nb(4)-O(11) bond length is 2.14 Å. The Nb(4)-O(6) bond length is 2.03 Å. The Nb(4)-O(9) bond length is 1.85 Å. In the fifth Nb site, Nb(5) is bonded to one O(11), one O(12), one O(13), one O(16), and one O(4) atom to form a mixture of corner and edge-sharing NbO5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 2-42°. The Nb(5)-O(11) bond length is 2.04 Å. The Nb(5)-O(12) bond length is 1.82 Å. The Nb(5)-O(13) bond length is 1.90 Å. The Nb(5)-O(16) bond length is 2.18 Å. The Nb(5)-O(4) bond length is 1.99 Å. In the sixth Nb site, Nb(6) is bonded to one O(1), one O(10), one O(13), one O(14), one O(15), and one O(5) atom to form distorted NbO6 octahedra that share  a cornercorner with one U(1)O6 octahedra,  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(5)O5 trigonal bipyramid, and  an edgeedge with one U(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 32-45°. The Nb(6)-O(1) bond length is 2.16 Å. The Nb(6)-O(10) bond length is 2.11 Å. The Nb(6)-O(13) bond length is 1.95 Å. The Nb(6)-O(14) bond length is 1.89 Å. The Nb(6)-O(15) bond length is 2.14 Å. The Nb(6)-O(5) bond length is 2.04 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to one U(1), one Nb(1), and one Nb(6) atom. In the second O site, O(2) is bonded in a water-like geometry to one U(1) and one Nb(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Nb(1) and one Nb(2) atom. In the fourth O site, O(4) is bonded in a linear geometry to one Nb(2) and one Nb(5) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Nb(2), one Nb(3), and one Nb(6) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Nb(2), one Nb(3), and one Nb(4) atom. In the seventh O site, O(7) is bonded in a single-bond geometry to one Nb(3) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one U(1) and one Nb(3) atom. In the ninth O site, O(9) is bonded in a bent 120 degrees geometry to one U(1) and one Nb(4) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Nb(4) and one Nb(6) atom. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Nb(3), one Nb(4), and one Nb(5) atom. In the twelfth O site, O(12) is bonded in a water-like geometry to one Nb(2) and one Nb(5) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Nb(5) and one Nb(6) atom. In the fourteenth O site, O(14) is bonded in a water-like geometry to one U(1) and one Nb(6) atom. In the fifteenth O site, O(15) is bonded in a distorted T-shaped geometry to one U(1), one Nb(1), and one Nb(6) atom. In the sixteenth O site, O(16) is bonded in a water-like geometry to one Nb(2) and one Nb(5) atom.