Tm2Sb2O7 crystallizes in the orthorhombic Ima2 space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted TmO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with four equivalent Sb(2)O6 octahedra, and edges with two equivalent Sb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-67°. In the second Tm site, Tm(2) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(2) atoms. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted SbO6 octahedra that share corners with two equivalent Tm(1)O6 octahedra, corners with four equivalent Sb(2)O6 octahedra, and edges with two equivalent Tm(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-67°. In the second Sb site, Sb(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form SbO6 octahedra that share corners with two equivalent Sb(2)O6 octahedra, corners with four equivalent Tm(1)O6 octahedra, and corners with four equivalent Sb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-66°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Tm(1), one Tm(2), one Sb(1), and one Sb(2) atom to form distorted OTm2Sb2 tetrahedra that share corners with four equivalent O(2)Tm3Sb tetrahedra, edges with two equivalent O(1)Tm2Sb2 tetrahedra, and edges with two equivalent O(2)Tm3Sb tetrahedra. In the second O site, O(2) is bonded to one Tm(1), two equivalent Tm(2), and one Sb(1) atom to form OTm3Sb tetrahedra that share corners with four equivalent O(1)Tm2Sb2 tetrahedra, corners with six equivalent O(2)Tm3Sb tetrahedra,  an edgeedge with one O(2)Tm3Sb tetrahedra, and edges with two equivalent O(1)Tm2Sb2 tetrahedra. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Tm(1), one Sb(1), and one Sb(2) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Sb(2) atoms.
Tm2Sb2O7 crystallizes in the orthorhombic Ima2 space group. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted TmO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with four equivalent Sb(2)O6 octahedra, and edges with two equivalent Sb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-67°. Both Tm(1)-O(1) bond lengths are 2.26 Å. Both Tm(1)-O(2) bond lengths are 2.25 Å. Both Tm(1)-O(3) bond lengths are 2.33 Å. In the second Tm site, Tm(2) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(2) atoms. Both Tm(2)-O(1) bond lengths are 2.29 Å. There are two shorter (2.34 Å) and two longer (2.44 Å) Tm(2)-O(2) bond lengths. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted SbO6 octahedra that share corners with two equivalent Tm(1)O6 octahedra, corners with four equivalent Sb(2)O6 octahedra, and edges with two equivalent Tm(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-67°. Both Sb(1)-O(1) bond lengths are 2.61 Å. Both Sb(1)-O(2) bond lengths are 2.28 Å. Both Sb(1)-O(3) bond lengths are 2.18 Å. In the second Sb site, Sb(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form SbO6 octahedra that share corners with two equivalent Sb(2)O6 octahedra, corners with four equivalent Tm(1)O6 octahedra, and corners with four equivalent Sb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-66°. Both Sb(2)-O(1) bond lengths are 2.00 Å. Both Sb(2)-O(3) bond lengths are 2.01 Å. Both Sb(2)-O(4) bond lengths are 1.92 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Tm(1), one Tm(2), one Sb(1), and one Sb(2) atom to form distorted OTm2Sb2 tetrahedra that share corners with four equivalent O(2)Tm3Sb tetrahedra, edges with two equivalent O(1)Tm2Sb2 tetrahedra, and edges with two equivalent O(2)Tm3Sb tetrahedra. In the second O site, O(2) is bonded to one Tm(1), two equivalent Tm(2), and one Sb(1) atom to form OTm3Sb tetrahedra that share corners with four equivalent O(1)Tm2Sb2 tetrahedra, corners with six equivalent O(2)Tm3Sb tetrahedra,  an edgeedge with one O(2)Tm3Sb tetrahedra, and edges with two equivalent O(1)Tm2Sb2 tetrahedra. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Tm(1), one Sb(1), and one Sb(2) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Sb(2) atoms.