MgTb2Ti2S2O5 crystallizes in the monoclinic Cm space group. Mg(1) is bonded in a 5-coordinate geometry to one S(2) and four equivalent O(2) atoms. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 8-coordinate geometry to four equivalent S(1) and four equivalent O(1) atoms. In the second Tb site, Tb(2) is bonded to one S(1) and four equivalent S(2) atoms to form a mixture of distorted corner and edge-sharing TbS5 trigonal bipyramids. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 5-coordinate geometry to one O(3) and four equivalent O(1) atoms. In the second Ti site, Ti(2) is bonded in a 5-coordinate geometry to one O(3) and four equivalent O(2) atoms. There are two inequivalent S sites. In the first S site, S(1) is bonded in a 5-coordinate geometry to one Tb(2) and four equivalent Tb(1) atoms. In the second S site, S(2) is bonded to one Mg(1) and four equivalent Tb(2) atoms to form distorted STb4Mg trigonal bipyramids that share corners with four equivalent S(2)Tb4Mg trigonal bipyramids, corners with four equivalent O(2)Mg2Ti2 trigonal pyramids, and edges with four equivalent S(2)Tb4Mg trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Tb(1) and two equivalent Ti(1) atoms to form a mixture of corner and edge-sharing OTb2Ti2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Ti(2) atoms to form distorted OMg2Ti2 trigonal pyramids that share corners with two equivalent S(2)Tb4Mg trigonal bipyramids, corners with four equivalent O(2)Mg2Ti2 trigonal pyramids, and edges with four equivalent O(2)Mg2Ti2 trigonal pyramids. In the third O site, O(3) is bonded in a linear geometry to one Ti(1) and one Ti(2) atom.
MgTb2Ti2S2O5 crystallizes in the monoclinic Cm space group. Mg(1) is bonded in a 5-coordinate geometry to one S(2) and four equivalent O(2) atoms. The Mg(1)-S(2) bond length is 2.57 Å. All Mg(1)-O(2) bond lengths are 2.02 Å. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 8-coordinate geometry to four equivalent S(1) and four equivalent O(1) atoms. There is one shorter (3.00 Å) and three longer (3.01 Å) Tb(1)-S(1) bond lengths. All Tb(1)-O(1) bond lengths are 2.29 Å. In the second Tb site, Tb(2) is bonded to one S(1) and four equivalent S(2) atoms to form a mixture of distorted corner and edge-sharing TbS5 trigonal bipyramids. The Tb(2)-S(1) bond length is 2.61 Å. There are three shorter (2.77 Å) and one longer (2.78 Å) Tb(2)-S(2) bond length. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 5-coordinate geometry to one O(3) and four equivalent O(1) atoms. The Ti(1)-O(3) bond length is 1.82 Å. All Ti(1)-O(1) bond lengths are 2.02 Å. In the second Ti site, Ti(2) is bonded in a 5-coordinate geometry to one O(3) and four equivalent O(2) atoms. The Ti(2)-O(3) bond length is 1.82 Å. All Ti(2)-O(2) bond lengths are 2.03 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded in a 5-coordinate geometry to one Tb(2) and four equivalent Tb(1) atoms. In the second S site, S(2) is bonded to one Mg(1) and four equivalent Tb(2) atoms to form distorted STb4Mg trigonal bipyramids that share corners with four equivalent S(2)Tb4Mg trigonal bipyramids, corners with four equivalent O(2)Mg2Ti2 trigonal pyramids, and edges with four equivalent S(2)Tb4Mg trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Tb(1) and two equivalent Ti(1) atoms to form a mixture of corner and edge-sharing OTb2Ti2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Ti(2) atoms to form distorted OMg2Ti2 trigonal pyramids that share corners with two equivalent S(2)Tb4Mg trigonal bipyramids, corners with four equivalent O(2)Mg2Ti2 trigonal pyramids, and edges with four equivalent O(2)Mg2Ti2 trigonal pyramids. In the third O site, O(3) is bonded in a linear geometry to one Ti(1) and one Ti(2) atom.