CuNbO3 crystallizes in the monoclinic C2/m space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form a mixture of distorted edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 8°. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form a mixture of distorted edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 8°. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a linear geometry to two equivalent O(3) atoms. In the second Cu site, Cu(2) is bonded in a linear geometry to one O(1) and one O(2) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Nb(2) and one Cu(2) atom. In the second O site, O(2) is bonded to one Nb(2), two equivalent Nb(1), and one Cu(2) atom to form distorted edge-sharing ONb3Cu tetrahedra. In the third O site, O(3) is bonded in a trigonal non-coplanar geometry to one Nb(1), one Nb(2), and one Cu(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom.
CuNbO3 crystallizes in the monoclinic C2/m space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form a mixture of distorted edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 8°. Both Nb(1)-O(2) bond lengths are 2.17 Å. Both Nb(1)-O(3) bond lengths are 2.03 Å. Both Nb(1)-O(4) bond lengths are 1.89 Å. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form a mixture of distorted edge and corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 8°. The Nb(2)-O(1) bond length is 1.82 Å. The Nb(2)-O(2) bond length is 2.28 Å. Both Nb(2)-O(3) bond lengths are 2.07 Å. Both Nb(2)-O(4) bond lengths are 1.98 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a linear geometry to two equivalent O(3) atoms. Both Cu(1)-O(3) bond lengths are 1.86 Å. In the second Cu site, Cu(2) is bonded in a linear geometry to one O(1) and one O(2) atom. The Cu(2)-O(1) bond length is 1.79 Å. The Cu(2)-O(2) bond length is 1.83 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Nb(2) and one Cu(2) atom. In the second O site, O(2) is bonded to one Nb(2), two equivalent Nb(1), and one Cu(2) atom to form distorted edge-sharing ONb3Cu tetrahedra. In the third O site, O(3) is bonded in a trigonal non-coplanar geometry to one Nb(1), one Nb(2), and one Cu(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to one Nb(1) and one Nb(2) atom.