Tb3OsO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. In the second Tb site, Tb(2) is bonded to one O(3), two equivalent O(2), and four equivalent O(1) atoms to form distorted TbO7 pentagonal bipyramids that share corners with two equivalent Os(1)O6 octahedra, corners with three equivalent Tb(2)O7 pentagonal bipyramids, edges with two equivalent Os(1)O6 octahedra, and edges with two equivalent Tb(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 38°. Os(1) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form OsO6 octahedra that share corners with two equivalent Os(1)O6 octahedra, corners with four equivalent Tb(2)O7 pentagonal bipyramids, and edges with four equivalent Tb(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Tb(1), two equivalent Tb(2), and one Os(1) atom to form distorted OTb3Os trigonal pyramids that share corners with four equivalent O(2)Tb4 tetrahedra, corners with eight equivalent O(1)Tb3Os trigonal pyramids, edges with two equivalent O(2)Tb4 tetrahedra, and edges with two equivalent O(1)Tb3Os trigonal pyramids. In the second O site, O(2) is bonded to two equivalent Tb(1) and two equivalent Tb(2) atoms to form OTb4 tetrahedra that share corners with six equivalent O(2)Tb4 tetrahedra, corners with eight equivalent O(1)Tb3Os trigonal pyramids,  an edgeedge with one O(2)Tb4 tetrahedra, and edges with four equivalent O(1)Tb3Os trigonal pyramids. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Tb(2) and two equivalent Os(1) atoms.
Tb3OsO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. All Tb(1)-O(1) bond lengths are 2.65 Å. All Tb(1)-O(2) bond lengths are 2.32 Å. In the second Tb site, Tb(2) is bonded to one O(3), two equivalent O(2), and four equivalent O(1) atoms to form distorted TbO7 pentagonal bipyramids that share corners with two equivalent Os(1)O6 octahedra, corners with three equivalent Tb(2)O7 pentagonal bipyramids, edges with two equivalent Os(1)O6 octahedra, and edges with two equivalent Tb(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 38°. The Tb(2)-O(3) bond length is 2.52 Å. There is one shorter (2.22 Å) and one longer (2.24 Å) Tb(2)-O(2) bond length. There are two shorter (2.32 Å) and two longer (2.36 Å) Tb(2)-O(1) bond lengths. Os(1) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form OsO6 octahedra that share corners with two equivalent Os(1)O6 octahedra, corners with four equivalent Tb(2)O7 pentagonal bipyramids, and edges with four equivalent Tb(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. Both Os(1)-O(3) bond lengths are 1.96 Å. All Os(1)-O(1) bond lengths are 1.96 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Tb(1), two equivalent Tb(2), and one Os(1) atom to form distorted OTb3Os trigonal pyramids that share corners with four equivalent O(2)Tb4 tetrahedra, corners with eight equivalent O(1)Tb3Os trigonal pyramids, edges with two equivalent O(2)Tb4 tetrahedra, and edges with two equivalent O(1)Tb3Os trigonal pyramids. In the second O site, O(2) is bonded to two equivalent Tb(1) and two equivalent Tb(2) atoms to form OTb4 tetrahedra that share corners with six equivalent O(2)Tb4 tetrahedra, corners with eight equivalent O(1)Tb3Os trigonal pyramids,  an edgeedge with one O(2)Tb4 tetrahedra, and edges with four equivalent O(1)Tb3Os trigonal pyramids. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Tb(2) and two equivalent Os(1) atoms.