Nd3NbO7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(3) atoms. In the second Nd site, Nd(2) is bonded to one O(2), two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted NdO7 pentagonal bipyramids that share corners with two equivalent Nb(1)O6 octahedra, corners with three equivalent Nd(2)O7 pentagonal bipyramids, edges with two equivalent Nb(1)O6 octahedra, and edges with two equivalent Nd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 30-42°. Nb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Nd(2)O7 pentagonal bipyramids, and edges with four equivalent Nd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 37°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Nd(1), two equivalent Nd(2), and one Nb(1) atom to form distorted ONd3Nb tetrahedra that share corners with four equivalent O(3)Nd4 tetrahedra, edges with two equivalent O(1)Nd3Nb tetrahedra, and edges with two equivalent O(3)Nd4 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Nd(2) and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded to two equivalent Nd(1) and two equivalent Nd(2) atoms to form ONd4 tetrahedra that share corners with four equivalent O(1)Nd3Nb tetrahedra, corners with six equivalent O(3)Nd4 tetrahedra,  an edgeedge with one O(3)Nd4 tetrahedra, and edges with two equivalent O(1)Nd3Nb tetrahedra. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Nd(2) and one Nb(1) atom.
Nd3NbO7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(3) atoms. Both Nd(1)-O(1) bond lengths are 2.41 Å. There are two shorter (2.41 Å) and two longer (2.44 Å) Nd(1)-O(3) bond lengths. In the second Nd site, Nd(2) is bonded to one O(2), two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted NdO7 pentagonal bipyramids that share corners with two equivalent Nb(1)O6 octahedra, corners with three equivalent Nd(2)O7 pentagonal bipyramids, edges with two equivalent Nb(1)O6 octahedra, and edges with two equivalent Nd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 30-42°. The Nd(2)-O(2) bond length is 2.65 Å. There is one shorter (2.43 Å) and one longer (2.46 Å) Nd(2)-O(1) bond length. There is one shorter (2.33 Å) and one longer (2.34 Å) Nd(2)-O(3) bond length. There is one shorter (2.43 Å) and one longer (2.48 Å) Nd(2)-O(4) bond length. Nb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Nd(2)O7 pentagonal bipyramids, and edges with four equivalent Nd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 37°. Both Nb(1)-O(1) bond lengths are 2.07 Å. There is one shorter (1.95 Å) and one longer (2.07 Å) Nb(1)-O(2) bond length. Both Nb(1)-O(4) bond lengths are 1.95 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Nd(1), two equivalent Nd(2), and one Nb(1) atom to form distorted ONd3Nb tetrahedra that share corners with four equivalent O(3)Nd4 tetrahedra, edges with two equivalent O(1)Nd3Nb tetrahedra, and edges with two equivalent O(3)Nd4 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Nd(2) and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded to two equivalent Nd(1) and two equivalent Nd(2) atoms to form ONd4 tetrahedra that share corners with four equivalent O(1)Nd3Nb tetrahedra, corners with six equivalent O(3)Nd4 tetrahedra,  an edgeedge with one O(3)Nd4 tetrahedra, and edges with two equivalent O(1)Nd3Nb tetrahedra. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Nd(2) and one Nb(1) atom.