Gd3SbO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded in a body-centered cubic geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(1) atoms. In the second Gd site, Gd(2) is bonded to one O(2), one O(3), one O(4), and four equivalent O(1) atoms to form distorted GdO7 pentagonal bipyramids that share corners with two equivalent Sb(1)O6 octahedra,  a cornercorner with one Gd(2)O7 pentagonal bipyramid, edges with two equivalent Sb(1)O6 octahedra, and edges with three equivalent Gd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 46°. Sb(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form SbO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with four equivalent Gd(2)O7 pentagonal bipyramids, and edges with four equivalent Gd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Gd(1), two equivalent Gd(2), and one Sb(1) atom to form distorted OGd3Sb tetrahedra that share corners with two equivalent O(3)Gd4 tetrahedra, corners with two equivalent O(4)Gd4 tetrahedra, corners with eight equivalent O(1)Gd3Sb tetrahedra, corners with two equivalent O(2)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(3)Gd4 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, edges with two equivalent O(1)Gd3Sb tetrahedra, and  an edgeedge with one O(2)Gd2Sb2 trigonal pyramid. In the second O site, O(2) is bonded to two equivalent Gd(2) and two equivalent Sb(1) atoms to form distorted OGd2Sb2 trigonal pyramids that share corners with two equivalent O(3)Gd4 tetrahedra, corners with eight equivalent O(1)Gd3Sb tetrahedra, corners with two equivalent O(2)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with four equivalent O(1)Gd3Sb tetrahedra. In the third O site, O(3) 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)Gd4 tetrahedra, corners with four equivalent O(4)Gd4 tetrahedra, corners with eight equivalent O(1)Gd3Sb tetrahedra, corners with two equivalent O(2)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with four equivalent O(1)Gd3Sb 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(4)Gd4 tetrahedra, corners with four equivalent O(3)Gd4 tetrahedra, corners with eight equivalent O(1)Gd3Sb tetrahedra,  an edgeedge with one O(3)Gd4 tetrahedra, edges with four equivalent O(1)Gd3Sb tetrahedra, and  an edgeedge with one O(2)Gd2Sb2 trigonal pyramid.
Gd3SbO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded in a body-centered cubic geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(1) atoms. Both Gd(1)-O(3) bond lengths are 2.34 Å. Both Gd(1)-O(4) bond lengths are 2.38 Å. All Gd(1)-O(1) bond lengths are 2.66 Å. In the second Gd site, Gd(2) is bonded to one O(2), one O(3), one O(4), and four equivalent O(1) atoms to form distorted GdO7 pentagonal bipyramids that share corners with two equivalent Sb(1)O6 octahedra,  a cornercorner with one Gd(2)O7 pentagonal bipyramid, edges with two equivalent Sb(1)O6 octahedra, and edges with three equivalent Gd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 46°. The Gd(2)-O(2) bond length is 2.52 Å. The Gd(2)-O(3) bond length is 2.28 Å. The Gd(2)-O(4) bond length is 2.24 Å. There are two shorter (2.32 Å) and two longer (2.44 Å) Gd(2)-O(1) bond lengths. Sb(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form SbO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with four equivalent Gd(2)O7 pentagonal bipyramids, and edges with four equivalent Gd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. Both Sb(1)-O(2) bond lengths are 2.01 Å. All Sb(1)-O(1) bond lengths are 1.97 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Gd(1), two equivalent Gd(2), and one Sb(1) atom to form distorted OGd3Sb tetrahedra that share corners with two equivalent O(3)Gd4 tetrahedra, corners with two equivalent O(4)Gd4 tetrahedra, corners with eight equivalent O(1)Gd3Sb tetrahedra, corners with two equivalent O(2)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(3)Gd4 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, edges with two equivalent O(1)Gd3Sb tetrahedra, and  an edgeedge with one O(2)Gd2Sb2 trigonal pyramid. In the second O site, O(2) is bonded to two equivalent Gd(2) and two equivalent Sb(1) atoms to form distorted OGd2Sb2 trigonal pyramids that share corners with two equivalent O(3)Gd4 tetrahedra, corners with eight equivalent O(1)Gd3Sb tetrahedra, corners with two equivalent O(2)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with four equivalent O(1)Gd3Sb tetrahedra. In the third O site, O(3) 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)Gd4 tetrahedra, corners with four equivalent O(4)Gd4 tetrahedra, corners with eight equivalent O(1)Gd3Sb tetrahedra, corners with two equivalent O(2)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with four equivalent O(1)Gd3Sb 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(4)Gd4 tetrahedra, corners with four equivalent O(3)Gd4 tetrahedra, corners with eight equivalent O(1)Gd3Sb tetrahedra,  an edgeedge with one O(3)Gd4 tetrahedra, edges with four equivalent O(1)Gd3Sb tetrahedra, and  an edgeedge with one O(2)Gd2Sb2 trigonal pyramid.