Gd2FeSbO7 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(2), two equivalent O(4), and four equivalent O(3) atoms to form distorted GdO8 hexagonal bipyramids that share edges with two equivalent Gd(1)O8 hexagonal bipyramids, edges with two equivalent Fe(1)O6 octahedra, and edges with four equivalent Sb(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(4), and four equivalent O(3) atoms. Fe(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with four equivalent Sb(1)O6 octahedra, and edges with two equivalent Gd(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 50-52°. Sb(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form SbO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with four equivalent Fe(1)O6 octahedra, and edges with four equivalent Gd(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-50°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Gd(2) and two equivalent Fe(1) atoms to form distorted OGd2Fe2 tetrahedra that share corners with two equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(1)Gd2Fe2 tetrahedra, corners with eight equivalent O(3)Gd2FeSb tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with four equivalent O(3)Gd2FeSb tetrahedra. In the second O site, O(2) is bonded to two equivalent Gd(1) and two equivalent Sb(1) atoms to form distorted OGd2Sb2 tetrahedra that share corners with two equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(2)Gd2Sb2 tetrahedra, corners with eight equivalent O(3)Gd2FeSb tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with four equivalent O(3)Gd2FeSb tetrahedra. In the third O site, O(3) is bonded to one Gd(1), one Gd(2), one Fe(1), and one Sb(1) atom to form distorted OGd2FeSb tetrahedra that share corners with two equivalent O(1)Gd2Fe2 tetrahedra, corners with two equivalent O(2)Gd2Sb2 tetrahedra, corners with two equivalent O(4)Gd4 tetrahedra, corners with eight equivalent O(3)Gd2FeSb tetrahedra,  an edgeedge with one O(1)Gd2Fe2 tetrahedra,  an edgeedge with one O(2)Gd2Sb2 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with two equivalent O(3)Gd2FeSb tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Gd(1) and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share corners with two equivalent O(1)Gd2Fe2 tetrahedra, corners with two equivalent O(2)Gd2Sb2 tetrahedra, corners with four equivalent O(4)Gd4 tetrahedra, corners with eight equivalent O(3)Gd2FeSb tetrahedra,  an edgeedge with one O(1)Gd2Fe2 tetrahedra,  an edgeedge with one O(2)Gd2Sb2 tetrahedra, and edges with four equivalent O(3)Gd2FeSb tetrahedra.
Gd2FeSbO7 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(2), two equivalent O(4), and four equivalent O(3) atoms to form distorted GdO8 hexagonal bipyramids that share edges with two equivalent Gd(1)O8 hexagonal bipyramids, edges with two equivalent Fe(1)O6 octahedra, and edges with four equivalent Sb(1)O6 octahedra. Both Gd(1)-O(2) bond lengths are 2.54 Å. Both Gd(1)-O(4) bond lengths are 2.22 Å. All Gd(1)-O(3) bond lengths are 2.51 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(4), and four equivalent O(3) atoms. Both Gd(2)-O(1) bond lengths are 2.51 Å. Both Gd(2)-O(4) bond lengths are 2.26 Å. All Gd(2)-O(3) bond lengths are 2.54 Å. Fe(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with four equivalent Sb(1)O6 octahedra, and edges with two equivalent Gd(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 50-52°. Both Fe(1)-O(1) bond lengths are 2.03 Å. All Fe(1)-O(3) bond lengths are 2.05 Å. Sb(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form SbO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with four equivalent Fe(1)O6 octahedra, and edges with four equivalent Gd(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-50°. Both Sb(1)-O(2) bond lengths are 2.02 Å. All Sb(1)-O(3) bond lengths are 1.99 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Gd(2) and two equivalent Fe(1) atoms to form distorted OGd2Fe2 tetrahedra that share corners with two equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(1)Gd2Fe2 tetrahedra, corners with eight equivalent O(3)Gd2FeSb tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with four equivalent O(3)Gd2FeSb tetrahedra. In the second O site, O(2) is bonded to two equivalent Gd(1) and two equivalent Sb(1) atoms to form distorted OGd2Sb2 tetrahedra that share corners with two equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(2)Gd2Sb2 tetrahedra, corners with eight equivalent O(3)Gd2FeSb tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with four equivalent O(3)Gd2FeSb tetrahedra. In the third O site, O(3) is bonded to one Gd(1), one Gd(2), one Fe(1), and one Sb(1) atom to form distorted OGd2FeSb tetrahedra that share corners with two equivalent O(1)Gd2Fe2 tetrahedra, corners with two equivalent O(2)Gd2Sb2 tetrahedra, corners with two equivalent O(4)Gd4 tetrahedra, corners with eight equivalent O(3)Gd2FeSb tetrahedra,  an edgeedge with one O(1)Gd2Fe2 tetrahedra,  an edgeedge with one O(2)Gd2Sb2 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with two equivalent O(3)Gd2FeSb tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Gd(1) and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share corners with two equivalent O(1)Gd2Fe2 tetrahedra, corners with two equivalent O(2)Gd2Sb2 tetrahedra, corners with four equivalent O(4)Gd4 tetrahedra, corners with eight equivalent O(3)Gd2FeSb tetrahedra,  an edgeedge with one O(1)Gd2Fe2 tetrahedra,  an edgeedge with one O(2)Gd2Sb2 tetrahedra, and edges with four equivalent O(3)Gd2FeSb tetrahedra.