Sm3SbO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Sm sites. In the first Sm site, Sm(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 Sm site, Sm(2) is bonded to one O(2), one O(3), one O(4), and four equivalent O(1) atoms to form distorted SmO7 pentagonal bipyramids that share corners with two equivalent Sb(1)O6 octahedra,  a cornercorner with one Sm(2)O7 pentagonal bipyramid, edges with two equivalent Sb(1)O6 octahedra, and edges with three equivalent Sm(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 Sm(2)O7 pentagonal bipyramids, and edges with four equivalent Sm(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 39°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Sm(1), two equivalent Sm(2), and one Sb(1) atom. In the second O site, O(2) is bonded to two equivalent Sm(2) and two equivalent Sb(1) atoms to form distorted OSm2Sb2 trigonal pyramids that share corners with two equivalent O(3)Sm4 tetrahedra, corners with two equivalent O(2)Sm2Sb2 trigonal pyramids, and  an edgeedge with one O(4)Sm4 tetrahedra. In the third O site, O(3) is bonded to two equivalent Sm(1) and two equivalent Sm(2) atoms to form OSm4 tetrahedra that share corners with two equivalent O(3)Sm4 tetrahedra, corners with four equivalent O(4)Sm4 tetrahedra, corners with two equivalent O(2)Sm2Sb2 trigonal pyramids, and  an edgeedge with one O(4)Sm4 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Sm(1) and two equivalent Sm(2) atoms to form OSm4 tetrahedra that share corners with two equivalent O(4)Sm4 tetrahedra, corners with four equivalent O(3)Sm4 tetrahedra,  an edgeedge with one O(3)Sm4 tetrahedra, and  an edgeedge with one O(2)Sm2Sb2 trigonal pyramid.
Sm3SbO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Sm sites. In the first Sm site, Sm(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 Sm(1)-O(3) bond lengths are 2.36 Å. Both Sm(1)-O(4) bond lengths are 2.39 Å. All Sm(1)-O(1) bond lengths are 2.68 Å. In the second Sm site, Sm(2) is bonded to one O(2), one O(3), one O(4), and four equivalent O(1) atoms to form distorted SmO7 pentagonal bipyramids that share corners with two equivalent Sb(1)O6 octahedra,  a cornercorner with one Sm(2)O7 pentagonal bipyramid, edges with two equivalent Sb(1)O6 octahedra, and edges with three equivalent Sm(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 46°. The Sm(2)-O(2) bond length is 2.54 Å. The Sm(2)-O(3) bond length is 2.30 Å. The Sm(2)-O(4) bond length is 2.26 Å. There are two shorter (2.35 Å) and two longer (2.45 Å) Sm(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 Sm(2)O7 pentagonal bipyramids, and edges with four equivalent Sm(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 39°. Both Sb(1)-O(2) bond lengths are 2.02 Å. All Sb(1)-O(1) bond lengths are 1.98 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Sm(1), two equivalent Sm(2), and one Sb(1) atom. In the second O site, O(2) is bonded to two equivalent Sm(2) and two equivalent Sb(1) atoms to form distorted OSm2Sb2 trigonal pyramids that share corners with two equivalent O(3)Sm4 tetrahedra, corners with two equivalent O(2)Sm2Sb2 trigonal pyramids, and  an edgeedge with one O(4)Sm4 tetrahedra. In the third O site, O(3) is bonded to two equivalent Sm(1) and two equivalent Sm(2) atoms to form OSm4 tetrahedra that share corners with two equivalent O(3)Sm4 tetrahedra, corners with four equivalent O(4)Sm4 tetrahedra, corners with two equivalent O(2)Sm2Sb2 trigonal pyramids, and  an edgeedge with one O(4)Sm4 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Sm(1) and two equivalent Sm(2) atoms to form OSm4 tetrahedra that share corners with two equivalent O(4)Sm4 tetrahedra, corners with four equivalent O(3)Sm4 tetrahedra,  an edgeedge with one O(3)Sm4 tetrahedra, and  an edgeedge with one O(2)Sm2Sb2 trigonal pyramid.