Tb2TiO5 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one O(3), one O(5), two equivalent O(1), and three equivalent O(2) atoms to form distorted TbO7 hexagonal pyramids that share corners with two equivalent Tb(2)O7 pentagonal bipyramids,  a cornercorner with one Ti(1)O5 trigonal bipyramid, edges with four equivalent Tb(1)O7 hexagonal pyramids, edges with three equivalent Tb(2)O7 pentagonal bipyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. In the second Tb site, Tb(2) is bonded to one O(1), one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form distorted TbO7 pentagonal bipyramids that share corners with two equivalent Tb(1)O7 hexagonal pyramids, corners with three equivalent Ti(1)O5 trigonal bipyramids, edges with three equivalent Tb(1)O7 hexagonal pyramids, edges with two equivalent Tb(2)O7 pentagonal bipyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. Ti(1) is bonded to one O(1), one O(4), one O(5), and two equivalent O(3) atoms to form distorted TiO5 trigonal bipyramids that share  a cornercorner with one Tb(1)O7 hexagonal pyramid, corners with three equivalent Tb(2)O7 pentagonal bipyramids, corners with two equivalent Ti(1)O5 trigonal bipyramids, edges with two equivalent Tb(1)O7 hexagonal pyramids, and edges with two equivalent Tb(2)O7 pentagonal bipyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Tb(2), two equivalent Tb(1), and one Ti(1) atom to form OTb3Ti tetrahedra that share  a cornercorner with one O(3)Tb2Ti2 tetrahedra,  a cornercorner with one O(5)Tb3Ti tetrahedra, corners with two equivalent O(1)Tb3Ti tetrahedra, corners with five equivalent O(2)Tb4 tetrahedra,  an edgeedge with one O(2)Tb4 tetrahedra, edges with two equivalent O(3)Tb2Ti2 tetrahedra, and edges with two equivalent O(5)Tb3Ti tetrahedra. In the second O site, O(2) is bonded to one Tb(2) and three equivalent Tb(1) atoms to form OTb4 tetrahedra that share corners with two equivalent O(3)Tb2Ti2 tetrahedra, corners with two equivalent O(2)Tb4 tetrahedra, corners with five equivalent O(1)Tb3Ti tetrahedra, corners with five equivalent O(5)Tb3Ti tetrahedra,  an edgeedge with one O(3)Tb2Ti2 tetrahedra,  an edgeedge with one O(1)Tb3Ti tetrahedra, and edges with two equivalent O(2)Tb4 tetrahedra. In the third O site, O(3) is bonded to one Tb(1), one Tb(2), and two equivalent Ti(1) atoms to form distorted OTb2Ti2 tetrahedra that share  a cornercorner with one O(1)Tb3Ti tetrahedra,  a cornercorner with one O(5)Tb3Ti tetrahedra, corners with two equivalent O(3)Tb2Ti2 tetrahedra, corners with two equivalent O(2)Tb4 tetrahedra,  an edgeedge with one O(2)Tb4 tetrahedra, edges with two equivalent O(1)Tb3Ti tetrahedra, and edges with two equivalent O(5)Tb3Ti tetrahedra. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Tb(2) and one Ti(1) atom. In the fifth O site, O(5) is bonded to one Tb(1), two equivalent Tb(2), and one Ti(1) atom to form OTb3Ti tetrahedra that share  a cornercorner with one O(3)Tb2Ti2 tetrahedra,  a cornercorner with one O(1)Tb3Ti tetrahedra, corners with two equivalent O(5)Tb3Ti tetrahedra, corners with five equivalent O(2)Tb4 tetrahedra, edges with two equivalent O(3)Tb2Ti2 tetrahedra, and edges with two equivalent O(1)Tb3Ti tetrahedra.
Tb2TiO5 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one O(3), one O(5), two equivalent O(1), and three equivalent O(2) atoms to form distorted TbO7 hexagonal pyramids that share corners with two equivalent Tb(2)O7 pentagonal bipyramids,  a cornercorner with one Ti(1)O5 trigonal bipyramid, edges with four equivalent Tb(1)O7 hexagonal pyramids, edges with three equivalent Tb(2)O7 pentagonal bipyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. The Tb(1)-O(3) bond length is 2.36 Å. The Tb(1)-O(5) bond length is 2.32 Å. Both Tb(1)-O(1) bond lengths are 2.36 Å. All Tb(1)-O(2) bond lengths are 2.35 Å. In the second Tb site, Tb(2) is bonded to one O(1), one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form distorted TbO7 pentagonal bipyramids that share corners with two equivalent Tb(1)O7 hexagonal pyramids, corners with three equivalent Ti(1)O5 trigonal bipyramids, edges with three equivalent Tb(1)O7 hexagonal pyramids, edges with two equivalent Tb(2)O7 pentagonal bipyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. The Tb(2)-O(1) bond length is 2.34 Å. The Tb(2)-O(2) bond length is 2.31 Å. The Tb(2)-O(3) bond length is 2.38 Å. Both Tb(2)-O(4) bond lengths are 2.37 Å. Both Tb(2)-O(5) bond lengths are 2.28 Å. Ti(1) is bonded to one O(1), one O(4), one O(5), and two equivalent O(3) atoms to form distorted TiO5 trigonal bipyramids that share  a cornercorner with one Tb(1)O7 hexagonal pyramid, corners with three equivalent Tb(2)O7 pentagonal bipyramids, corners with two equivalent Ti(1)O5 trigonal bipyramids, edges with two equivalent Tb(1)O7 hexagonal pyramids, and edges with two equivalent Tb(2)O7 pentagonal bipyramids. The Ti(1)-O(1) bond length is 1.90 Å. The Ti(1)-O(4) bond length is 1.78 Å. The Ti(1)-O(5) bond length is 1.91 Å. Both Ti(1)-O(3) bond lengths are 1.96 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Tb(2), two equivalent Tb(1), and one Ti(1) atom to form OTb3Ti tetrahedra that share  a cornercorner with one O(3)Tb2Ti2 tetrahedra,  a cornercorner with one O(5)Tb3Ti tetrahedra, corners with two equivalent O(1)Tb3Ti tetrahedra, corners with five equivalent O(2)Tb4 tetrahedra,  an edgeedge with one O(2)Tb4 tetrahedra, edges with two equivalent O(3)Tb2Ti2 tetrahedra, and edges with two equivalent O(5)Tb3Ti tetrahedra. In the second O site, O(2) is bonded to one Tb(2) and three equivalent Tb(1) atoms to form OTb4 tetrahedra that share corners with two equivalent O(3)Tb2Ti2 tetrahedra, corners with two equivalent O(2)Tb4 tetrahedra, corners with five equivalent O(1)Tb3Ti tetrahedra, corners with five equivalent O(5)Tb3Ti tetrahedra,  an edgeedge with one O(3)Tb2Ti2 tetrahedra,  an edgeedge with one O(1)Tb3Ti tetrahedra, and edges with two equivalent O(2)Tb4 tetrahedra. In the third O site, O(3) is bonded to one Tb(1), one Tb(2), and two equivalent Ti(1) atoms to form distorted OTb2Ti2 tetrahedra that share  a cornercorner with one O(1)Tb3Ti tetrahedra,  a cornercorner with one O(5)Tb3Ti tetrahedra, corners with two equivalent O(3)Tb2Ti2 tetrahedra, corners with two equivalent O(2)Tb4 tetrahedra,  an edgeedge with one O(2)Tb4 tetrahedra, edges with two equivalent O(1)Tb3Ti tetrahedra, and edges with two equivalent O(5)Tb3Ti tetrahedra. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Tb(2) and one Ti(1) atom. In the fifth O site, O(5) is bonded to one Tb(1), two equivalent Tb(2), and one Ti(1) atom to form OTb3Ti tetrahedra that share  a cornercorner with one O(3)Tb2Ti2 tetrahedra,  a cornercorner with one O(1)Tb3Ti tetrahedra, corners with two equivalent O(5)Tb3Ti tetrahedra, corners with five equivalent O(2)Tb4 tetrahedra, edges with two equivalent O(3)Tb2Ti2 tetrahedra, and edges with two equivalent O(1)Tb3Ti tetrahedra.