Gd2NbGaO7 crystallizes in the orthorhombic Imma space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to two equivalent O(1), two equivalent O(2), and four equivalent O(4) atoms to form distorted GdO8 hexagonal bipyramids that share edges with two equivalent Gd(1)O8 hexagonal bipyramids, edges with two equivalent Ga(1)O6 octahedra, and edges with four equivalent Nb(1)O6 octahedra. In the second Gd site, Gd(2) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(4) atoms. Nb(1) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Ga(1)O6 octahedra, and edges with four equivalent Gd(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-49°. Ga(1) is bonded to two equivalent O(3) and four equivalent O(4) atoms to form GaO6 octahedra that share corners with two equivalent Ga(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and edges with two equivalent Gd(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 49-51°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Gd(1) and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share corners with two equivalent O(3)Gd2Ga2 tetrahedra, corners with two equivalent O(2)Gd2Nb2 tetrahedra, corners with four equivalent O(1)Gd4 tetrahedra, corners with eight equivalent O(4)Gd2NbGa tetrahedra,  an edgeedge with one O(3)Gd2Ga2 tetrahedra,  an edgeedge with one O(2)Gd2Nb2 tetrahedra, and edges with four equivalent O(4)Gd2NbGa tetrahedra. In the second O site, O(2) is bonded to two equivalent Gd(1) and two equivalent Nb(1) atoms to form distorted OGd2Nb2 tetrahedra that share corners with two equivalent O(1)Gd4 tetrahedra, corners with four equivalent O(2)Gd2Nb2 tetrahedra, corners with eight equivalent O(4)Gd2NbGa tetrahedra,  an edgeedge with one O(1)Gd4 tetrahedra, and edges with four equivalent O(4)Gd2NbGa tetrahedra. In the third O site, O(3) is bonded to two equivalent Gd(2) and two equivalent Ga(1) atoms to form distorted OGd2Ga2 tetrahedra that share corners with two equivalent O(1)Gd4 tetrahedra, corners with four equivalent O(3)Gd2Ga2 tetrahedra, corners with eight equivalent O(4)Gd2NbGa tetrahedra,  an edgeedge with one O(1)Gd4 tetrahedra, and edges with four equivalent O(4)Gd2NbGa tetrahedra. In the fourth O site, O(4) is bonded to one Gd(1), one Gd(2), one Nb(1), and one Ga(1) atom to form distorted OGd2NbGa tetrahedra that share corners with two equivalent O(3)Gd2Ga2 tetrahedra, corners with two equivalent O(2)Gd2Nb2 tetrahedra, corners with two equivalent O(1)Gd4 tetrahedra, corners with eight equivalent O(4)Gd2NbGa tetrahedra,  an edgeedge with one O(3)Gd2Ga2 tetrahedra,  an edgeedge with one O(2)Gd2Nb2 tetrahedra,  an edgeedge with one O(1)Gd4 tetrahedra, and edges with two equivalent O(4)Gd2NbGa tetrahedra.
Gd2NbGaO7 crystallizes in the orthorhombic Imma space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to two equivalent O(1), two equivalent O(2), and four equivalent O(4) atoms to form distorted GdO8 hexagonal bipyramids that share edges with two equivalent Gd(1)O8 hexagonal bipyramids, edges with two equivalent Ga(1)O6 octahedra, and edges with four equivalent Nb(1)O6 octahedra. Both Gd(1)-O(1) bond lengths are 2.23 Å. Both Gd(1)-O(2) bond lengths are 2.53 Å. All Gd(1)-O(4) bond lengths are 2.56 Å. In the second Gd site, Gd(2) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(4) atoms. Both Gd(2)-O(1) bond lengths are 2.27 Å. Both Gd(2)-O(3) bond lengths are 2.55 Å. All Gd(2)-O(4) bond lengths are 2.53 Å. Nb(1) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Ga(1)O6 octahedra, and edges with four equivalent Gd(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-49°. Both Nb(1)-O(2) bond lengths are 2.04 Å. All Nb(1)-O(4) bond lengths are 2.00 Å. Ga(1) is bonded to two equivalent O(3) and four equivalent O(4) atoms to form GaO6 octahedra that share corners with two equivalent Ga(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and edges with two equivalent Gd(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 49-51°. Both Ga(1)-O(3) bond lengths are 2.00 Å. All Ga(1)-O(4) bond lengths are 2.04 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Gd(1) and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share corners with two equivalent O(3)Gd2Ga2 tetrahedra, corners with two equivalent O(2)Gd2Nb2 tetrahedra, corners with four equivalent O(1)Gd4 tetrahedra, corners with eight equivalent O(4)Gd2NbGa tetrahedra,  an edgeedge with one O(3)Gd2Ga2 tetrahedra,  an edgeedge with one O(2)Gd2Nb2 tetrahedra, and edges with four equivalent O(4)Gd2NbGa tetrahedra. In the second O site, O(2) is bonded to two equivalent Gd(1) and two equivalent Nb(1) atoms to form distorted OGd2Nb2 tetrahedra that share corners with two equivalent O(1)Gd4 tetrahedra, corners with four equivalent O(2)Gd2Nb2 tetrahedra, corners with eight equivalent O(4)Gd2NbGa tetrahedra,  an edgeedge with one O(1)Gd4 tetrahedra, and edges with four equivalent O(4)Gd2NbGa tetrahedra. In the third O site, O(3) is bonded to two equivalent Gd(2) and two equivalent Ga(1) atoms to form distorted OGd2Ga2 tetrahedra that share corners with two equivalent O(1)Gd4 tetrahedra, corners with four equivalent O(3)Gd2Ga2 tetrahedra, corners with eight equivalent O(4)Gd2NbGa tetrahedra,  an edgeedge with one O(1)Gd4 tetrahedra, and edges with four equivalent O(4)Gd2NbGa tetrahedra. In the fourth O site, O(4) is bonded to one Gd(1), one Gd(2), one Nb(1), and one Ga(1) atom to form distorted OGd2NbGa tetrahedra that share corners with two equivalent O(3)Gd2Ga2 tetrahedra, corners with two equivalent O(2)Gd2Nb2 tetrahedra, corners with two equivalent O(1)Gd4 tetrahedra, corners with eight equivalent O(4)Gd2NbGa tetrahedra,  an edgeedge with one O(3)Gd2Ga2 tetrahedra,  an edgeedge with one O(2)Gd2Nb2 tetrahedra,  an edgeedge with one O(1)Gd4 tetrahedra, and edges with two equivalent O(4)Gd2NbGa tetrahedra.