MgTb2V2O8 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share corners with two equivalent V(1)O4 tetrahedra and edges with two equivalent V(1)O4 tetrahedra. Tb(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. V(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form VO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 56°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Tb(1), and one V(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Tb(1) and one V(1) atom. In the third O site, O(3) is bonded to one Mg(1), two equivalent Tb(1), and one V(1) atom to form distorted corner-sharing OTb2MgV trigonal pyramids. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Tb(1), and one V(1) atom.
MgTb2V2O8 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share corners with two equivalent V(1)O4 tetrahedra and edges with two equivalent V(1)O4 tetrahedra. Both Mg(1)-O(1) bond lengths are 2.40 Å. Both Mg(1)-O(3) bond lengths are 1.97 Å. Both Mg(1)-O(4) bond lengths are 2.07 Å. Tb(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There is one shorter (2.30 Å) and one longer (2.46 Å) Tb(1)-O(1) bond length. There is one shorter (2.28 Å) and one longer (2.40 Å) Tb(1)-O(2) bond length. There is one shorter (2.41 Å) and one longer (2.47 Å) Tb(1)-O(3) bond length. There is one shorter (2.42 Å) and one longer (2.82 Å) Tb(1)-O(4) bond length. V(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form VO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 56°. The V(1)-O(1) bond length is 1.88 Å. The V(1)-O(2) bond length is 1.77 Å. The V(1)-O(3) bond length is 1.89 Å. The V(1)-O(4) bond length is 1.78 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Tb(1), and one V(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Tb(1) and one V(1) atom. In the third O site, O(3) is bonded to one Mg(1), two equivalent Tb(1), and one V(1) atom to form distorted corner-sharing OTb2MgV trigonal pyramids. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Tb(1), and one V(1) atom.