Gd3SbO7 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to one O(1), one O(2), one O(4), two equivalent O(3), and two equivalent O(5) atoms to form distorted GdO7 pentagonal bipyramids that share corners with two equivalent Sb(1)O6 octahedra,  a cornercorner with one Gd(1)O7 pentagonal bipyramid, edges with two equivalent Sb(1)O6 octahedra, and edges with three equivalent Gd(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 45-48°. In the second Gd site, Gd(2) is bonded in a distorted body-centered cubic geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Sb(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form SbO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with four equivalent Gd(1)O7 pentagonal bipyramids, and edges with four equivalent Gd(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Gd(1) and two equivalent Sb(1) atoms to form distorted OGd2Sb2 trigonal pyramids that share corners with two equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(5)Gd3Sb tetrahedra, corners with two equivalent O(1)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(2)Gd4 tetrahedra, and edges with two equivalent O(5)Gd3Sb tetrahedra. In the second O site, O(2) is bonded to two equivalent Gd(1) and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share corners with two equivalent O(2)Gd4 tetrahedra, corners with four equivalent O(5)Gd3Sb tetrahedra, corners with four equivalent O(4)Gd4 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, edges with two equivalent O(5)Gd3Sb tetrahedra, and  an edgeedge with one O(1)Gd2Sb2 trigonal pyramid. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Gd(2), two equivalent Gd(1), and one Sb(1) atom. 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(5)Gd3Sb tetrahedra, corners with four equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(1)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(2)Gd4 tetrahedra, and edges with two equivalent O(5)Gd3Sb tetrahedra. In the fifth O site, O(5) is bonded to one Gd(2), two equivalent Gd(1), and one Sb(1) atom to form distorted OGd3Sb tetrahedra that share corners with two equivalent O(5)Gd3Sb tetrahedra, corners with two equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(4)Gd4 tetrahedra, corners with two equivalent O(1)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(5)Gd3Sb tetrahedra,  an edgeedge with one O(2)Gd4 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd2Sb2 trigonal pyramid.
Gd3SbO7 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to one O(1), one O(2), one O(4), two equivalent O(3), and two equivalent O(5) atoms to form distorted GdO7 pentagonal bipyramids that share corners with two equivalent Sb(1)O6 octahedra,  a cornercorner with one Gd(1)O7 pentagonal bipyramid, edges with two equivalent Sb(1)O6 octahedra, and edges with three equivalent Gd(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 45-48°. The Gd(1)-O(1) bond length is 2.52 Å. The Gd(1)-O(2) bond length is 2.25 Å. The Gd(1)-O(4) bond length is 2.31 Å. There is one shorter (2.32 Å) and one longer (2.45 Å) Gd(1)-O(3) bond length. There is one shorter (2.33 Å) and one longer (2.45 Å) Gd(1)-O(5) bond length. In the second Gd site, Gd(2) is bonded in a distorted body-centered cubic geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Both Gd(2)-O(2) bond lengths are 2.40 Å. Both Gd(2)-O(3) bond lengths are 2.80 Å. Both Gd(2)-O(4) bond lengths are 2.35 Å. Both Gd(2)-O(5) bond lengths are 2.57 Å. Sb(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form SbO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with four equivalent Gd(1)O7 pentagonal bipyramids, and edges with four equivalent Gd(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. Both Sb(1)-O(1) bond lengths are 2.03 Å. Both Sb(1)-O(3) bond lengths are 1.99 Å. Both Sb(1)-O(5) bond lengths are 2.01 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Gd(1) and two equivalent Sb(1) atoms to form distorted OGd2Sb2 trigonal pyramids that share corners with two equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(5)Gd3Sb tetrahedra, corners with two equivalent O(1)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(2)Gd4 tetrahedra, and edges with two equivalent O(5)Gd3Sb tetrahedra. In the second O site, O(2) is bonded to two equivalent Gd(1) and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share corners with two equivalent O(2)Gd4 tetrahedra, corners with four equivalent O(5)Gd3Sb tetrahedra, corners with four equivalent O(4)Gd4 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, edges with two equivalent O(5)Gd3Sb tetrahedra, and  an edgeedge with one O(1)Gd2Sb2 trigonal pyramid. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Gd(2), two equivalent Gd(1), and one Sb(1) atom. 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(5)Gd3Sb tetrahedra, corners with four equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(1)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(2)Gd4 tetrahedra, and edges with two equivalent O(5)Gd3Sb tetrahedra. In the fifth O site, O(5) is bonded to one Gd(2), two equivalent Gd(1), and one Sb(1) atom to form distorted OGd3Sb tetrahedra that share corners with two equivalent O(5)Gd3Sb tetrahedra, corners with two equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(4)Gd4 tetrahedra, corners with two equivalent O(1)Gd2Sb2 trigonal pyramids,  an edgeedge with one O(5)Gd3Sb tetrahedra,  an edgeedge with one O(2)Gd4 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd2Sb2 trigonal pyramid.