Gd3NbO7 crystallizes in the triclinic P-1 space group. There are three inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to one O(3), one O(4), one O(7), two equivalent O(2), and two equivalent O(6) atoms to form distorted GdO7 pentagonal bipyramids that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Gd(3)O7 pentagonal bipyramid,  an edgeedge with one Nb(1)O6 octahedra, edges with two equivalent Gd(1)O7 pentagonal bipyramids, and edges with two equivalent Gd(3)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 47-50°. In the second Gd site, Gd(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(6), two equivalent O(4), and two equivalent O(7) atoms. In the third Gd site, Gd(3) is bonded to one O(5), one O(6), one O(7), two equivalent O(1), and two equivalent O(3) atoms to form distorted GdO7 pentagonal bipyramids that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Gd(1)O7 pentagonal bipyramid,  an edgeedge with one Nb(1)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra, edges with two equivalent Gd(1)O7 pentagonal bipyramids, and edges with two equivalent Gd(3)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 44-45°. 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(5) atoms to form NbO6 octahedra that share corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Gd(1)O7 pentagonal bipyramids, corners with two equivalent Gd(3)O7 pentagonal bipyramids, edges with two equivalent Gd(1)O7 pentagonal bipyramids, and edges with two equivalent Gd(3)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. In the second Nb site, Nb(2) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Gd(1)O7 pentagonal bipyramids, corners with two equivalent Gd(3)O7 pentagonal bipyramids, and edges with two equivalent Gd(3)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Gd(2), two equivalent Gd(3), and one Nb(2) atom to form distorted OGd3Nb trigonal pyramids that share  a cornercorner with one O(6)Gd4 tetrahedra, corners with two equivalent O(4)Gd3Nb tetrahedra, corners with two equivalent O(7)Gd4 tetrahedra, corners with four equivalent O(3)Gd3Nb tetrahedra,  a cornercorner with one O(1)Gd3Nb trigonal pyramid,  an edgeedge with one O(4)Gd3Nb tetrahedra,  an edgeedge with one O(6)Gd4 tetrahedra,  an edgeedge with one O(7)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd3Nb trigonal pyramid. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Gd(2), two equivalent Gd(1), and one Nb(1) atom. In the third O site, O(3) is bonded to one Gd(1), two equivalent Gd(3), and one Nb(1) atom to form distorted OGd3Nb tetrahedra that share  a cornercorner with one O(3)Gd3Nb tetrahedra,  a cornercorner with one O(4)Gd3Nb tetrahedra,  a cornercorner with one O(7)Gd4 tetrahedra, corners with two equivalent O(6)Gd4 tetrahedra, corners with four equivalent O(1)Gd3Nb trigonal pyramids,  an edgeedge with one O(3)Gd3Nb tetrahedra,  an edgeedge with one O(6)Gd4 tetrahedra, and  an edgeedge with one O(7)Gd4 tetrahedra. In the fourth O site, O(4) is bonded to one Gd(1), two equivalent Gd(2), and one Nb(2) atom to form distorted OGd3Nb tetrahedra that share  a cornercorner with one O(3)Gd3Nb tetrahedra,  a cornercorner with one O(4)Gd3Nb tetrahedra, corners with three equivalent O(7)Gd4 tetrahedra, corners with four equivalent O(6)Gd4 tetrahedra, corners with two equivalent O(1)Gd3Nb trigonal pyramids,  an edgeedge with one O(4)Gd3Nb tetrahedra,  an edgeedge with one O(7)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd3Nb trigonal pyramid. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Gd(3), one Nb(1), and one Nb(2) atom. In the sixth O site, O(6) is bonded to one Gd(2), one Gd(3), and two equivalent Gd(1) atoms to form OGd4 tetrahedra that share corners with two equivalent O(3)Gd3Nb tetrahedra, corners with three equivalent O(7)Gd4 tetrahedra, corners with four equivalent O(4)Gd3Nb tetrahedra,  a cornercorner with one O(1)Gd3Nb trigonal pyramid,  an edgeedge with one O(3)Gd3Nb tetrahedra,  an edgeedge with one O(6)Gd4 tetrahedra,  an edgeedge with one O(7)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd3Nb trigonal pyramid. In the seventh O site, O(7) is bonded to one Gd(1), one Gd(3), and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share  a cornercorner with one O(3)Gd3Nb tetrahedra, corners with three equivalent O(4)Gd3Nb tetrahedra, corners with three equivalent O(6)Gd4 tetrahedra, corners with two equivalent O(1)Gd3Nb trigonal pyramids,  an edgeedge with one O(3)Gd3Nb tetrahedra,  an edgeedge with one O(4)Gd3Nb tetrahedra,  an edgeedge with one O(6)Gd4 tetrahedra,  an edgeedge with one O(7)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd3Nb trigonal pyramid.
Gd3NbO7 crystallizes in the triclinic P-1 space group. There are three inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to one O(3), one O(4), one O(7), two equivalent O(2), and two equivalent O(6) atoms to form distorted GdO7 pentagonal bipyramids that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Gd(3)O7 pentagonal bipyramid,  an edgeedge with one Nb(1)O6 octahedra, edges with two equivalent Gd(1)O7 pentagonal bipyramids, and edges with two equivalent Gd(3)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 47-50°. The Gd(1)-O(3) bond length is 2.45 Å. The Gd(1)-O(4) bond length is 2.39 Å. The Gd(1)-O(7) bond length is 2.33 Å. There is one shorter (2.37 Å) and one longer (2.48 Å) Gd(1)-O(2) bond length. There is one shorter (2.33 Å) and one longer (2.36 Å) Gd(1)-O(6) bond length. In the second Gd site, Gd(2) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(6), two equivalent O(4), and two equivalent O(7) atoms. The Gd(2)-O(1) bond length is 2.44 Å. The Gd(2)-O(2) bond length is 2.74 Å. The Gd(2)-O(6) bond length is 2.30 Å. There is one shorter (2.43 Å) and one longer (2.63 Å) Gd(2)-O(4) bond length. There is one shorter (2.24 Å) and one longer (2.29 Å) Gd(2)-O(7) bond length. In the third Gd site, Gd(3) is bonded to one O(5), one O(6), one O(7), two equivalent O(1), and two equivalent O(3) atoms to form distorted GdO7 pentagonal bipyramids that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Gd(1)O7 pentagonal bipyramid,  an edgeedge with one Nb(1)O6 octahedra,  an edgeedge with one Nb(2)O6 octahedra, edges with two equivalent Gd(1)O7 pentagonal bipyramids, and edges with two equivalent Gd(3)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 44-45°. The Gd(3)-O(5) bond length is 2.41 Å. The Gd(3)-O(6) bond length is 2.22 Å. The Gd(3)-O(7) bond length is 2.22 Å. There is one shorter (2.34 Å) and one longer (2.44 Å) Gd(3)-O(1) bond length. There is one shorter (2.32 Å) and one longer (2.42 Å) Gd(3)-O(3) bond length. 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(5) atoms to form NbO6 octahedra that share corners with two equivalent Nb(2)O6 octahedra, corners with two equivalent Gd(1)O7 pentagonal bipyramids, corners with two equivalent Gd(3)O7 pentagonal bipyramids, edges with two equivalent Gd(1)O7 pentagonal bipyramids, and edges with two equivalent Gd(3)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. Both Nb(1)-O(2) bond lengths are 2.01 Å. Both Nb(1)-O(3) bond lengths are 1.99 Å. Both Nb(1)-O(5) bond lengths are 2.01 Å. In the second Nb site, Nb(2) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with two equivalent Gd(1)O7 pentagonal bipyramids, corners with two equivalent Gd(3)O7 pentagonal bipyramids, and edges with two equivalent Gd(3)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. Both Nb(2)-O(1) bond lengths are 1.99 Å. Both Nb(2)-O(4) bond lengths are 2.06 Å. Both Nb(2)-O(5) bond lengths are 1.99 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Gd(2), two equivalent Gd(3), and one Nb(2) atom to form distorted OGd3Nb trigonal pyramids that share  a cornercorner with one O(6)Gd4 tetrahedra, corners with two equivalent O(4)Gd3Nb tetrahedra, corners with two equivalent O(7)Gd4 tetrahedra, corners with four equivalent O(3)Gd3Nb tetrahedra,  a cornercorner with one O(1)Gd3Nb trigonal pyramid,  an edgeedge with one O(4)Gd3Nb tetrahedra,  an edgeedge with one O(6)Gd4 tetrahedra,  an edgeedge with one O(7)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd3Nb trigonal pyramid. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Gd(2), two equivalent Gd(1), and one Nb(1) atom. In the third O site, O(3) is bonded to one Gd(1), two equivalent Gd(3), and one Nb(1) atom to form distorted OGd3Nb tetrahedra that share  a cornercorner with one O(3)Gd3Nb tetrahedra,  a cornercorner with one O(4)Gd3Nb tetrahedra,  a cornercorner with one O(7)Gd4 tetrahedra, corners with two equivalent O(6)Gd4 tetrahedra, corners with four equivalent O(1)Gd3Nb trigonal pyramids,  an edgeedge with one O(3)Gd3Nb tetrahedra,  an edgeedge with one O(6)Gd4 tetrahedra, and  an edgeedge with one O(7)Gd4 tetrahedra. In the fourth O site, O(4) is bonded to one Gd(1), two equivalent Gd(2), and one Nb(2) atom to form distorted OGd3Nb tetrahedra that share  a cornercorner with one O(3)Gd3Nb tetrahedra,  a cornercorner with one O(4)Gd3Nb tetrahedra, corners with three equivalent O(7)Gd4 tetrahedra, corners with four equivalent O(6)Gd4 tetrahedra, corners with two equivalent O(1)Gd3Nb trigonal pyramids,  an edgeedge with one O(4)Gd3Nb tetrahedra,  an edgeedge with one O(7)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd3Nb trigonal pyramid. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Gd(3), one Nb(1), and one Nb(2) atom. In the sixth O site, O(6) is bonded to one Gd(2), one Gd(3), and two equivalent Gd(1) atoms to form OGd4 tetrahedra that share corners with two equivalent O(3)Gd3Nb tetrahedra, corners with three equivalent O(7)Gd4 tetrahedra, corners with four equivalent O(4)Gd3Nb tetrahedra,  a cornercorner with one O(1)Gd3Nb trigonal pyramid,  an edgeedge with one O(3)Gd3Nb tetrahedra,  an edgeedge with one O(6)Gd4 tetrahedra,  an edgeedge with one O(7)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd3Nb trigonal pyramid. In the seventh O site, O(7) is bonded to one Gd(1), one Gd(3), and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share  a cornercorner with one O(3)Gd3Nb tetrahedra, corners with three equivalent O(4)Gd3Nb tetrahedra, corners with three equivalent O(6)Gd4 tetrahedra, corners with two equivalent O(1)Gd3Nb trigonal pyramids,  an edgeedge with one O(3)Gd3Nb tetrahedra,  an edgeedge with one O(4)Gd3Nb tetrahedra,  an edgeedge with one O(6)Gd4 tetrahedra,  an edgeedge with one O(7)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd3Nb trigonal pyramid.