UNb2O7 crystallizes in the orthorhombic Cmcm space group. U(1) is bonded to one O(2), two equivalent O(5), and four equivalent O(1) atoms to form distorted edge-sharing UO7 hexagonal pyramids. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms. In the second Nb site, Nb(2) is bonded in a 7-coordinate geometry to one O(4), two equivalent O(3), and four equivalent O(5) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to two equivalent U(1) and one Nb(1) atom. In the second O site, O(2) is bonded in a linear geometry to one U(1) and one Nb(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Nb(1) and two equivalent Nb(2) 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 distorted trigonal planar geometry to one U(1) and two equivalent Nb(2) atoms.
UNb2O7 crystallizes in the orthorhombic Cmcm space group. U(1) is bonded to one O(2), two equivalent O(5), and four equivalent O(1) atoms to form distorted edge-sharing UO7 hexagonal pyramids. The U(1)-O(2) bond length is 2.24 Å. Both U(1)-O(5) bond lengths are 2.30 Å. All U(1)-O(1) bond lengths are 2.30 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms. The Nb(1)-O(2) bond length is 1.84 Å. The Nb(1)-O(3) bond length is 2.45 Å. Both Nb(1)-O(1) bond lengths are 2.02 Å. Both Nb(1)-O(4) bond lengths are 2.00 Å. In the second Nb site, Nb(2) is bonded in a 7-coordinate geometry to one O(4), two equivalent O(3), and four equivalent O(5) atoms. The Nb(2)-O(4) bond length is 2.40 Å. Both Nb(2)-O(3) bond lengths are 1.98 Å. There are two shorter (2.02 Å) and two longer (2.15 Å) Nb(2)-O(5) bond lengths. There are five inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to two equivalent U(1) and one Nb(1) atom. In the second O site, O(2) is bonded in a linear geometry to one U(1) and one Nb(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Nb(1) and two equivalent Nb(2) 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 distorted trigonal planar geometry to one U(1) and two equivalent Nb(2) atoms.