Tb2TiO5 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 6-coordinate geometry to one O(3), two equivalent O(1), and three equivalent O(4) atoms. In the second Tb site, Tb(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form TbO6 octahedra that share corners with two equivalent Tb(2)O6 octahedra, corners with four equivalent Ti(1)O6 octahedra, and edges with two equivalent Tb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-65°. Ti(1) is bonded to one O(3), one O(4), one O(5), and three equivalent O(2) atoms to form distorted TiO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra, corners with four equivalent Tb(2)O6 octahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 35-64°. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Tb(1) and two equivalent Tb(2) atoms to form OTb4 tetrahedra that share corners with two equivalent O(3)Tb3Ti tetrahedra, corners with four equivalent O(4)Tb3Ti tetrahedra, corners with four equivalent O(1)Tb4 tetrahedra,  an edgeedge with one O(4)Tb3Ti tetrahedra, and edges with two equivalent O(3)Tb3Ti tetrahedra. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to three equivalent Ti(1) atoms. In the third O site, O(3) is bonded to one Tb(1), two equivalent Tb(2), and one Ti(1) atom to form OTb3Ti tetrahedra that share corners with two equivalent O(3)Tb3Ti tetrahedra, corners with two equivalent O(1)Tb4 tetrahedra, corners with four equivalent O(4)Tb3Ti tetrahedra, and edges with two equivalent O(1)Tb4 tetrahedra. In the fourth O site, O(4) is bonded to three equivalent Tb(1) and one Ti(1) atom to form OTb3Ti tetrahedra that share corners with two equivalent O(4)Tb3Ti tetrahedra, corners with four equivalent O(3)Tb3Ti tetrahedra, corners with four equivalent O(1)Tb4 tetrahedra,  an edgeedge with one O(1)Tb4 tetrahedra, and edges with two equivalent O(4)Tb3Ti tetrahedra. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Tb(2) and one Ti(1) atom.
Tb2TiO5 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 6-coordinate geometry to one O(3), two equivalent O(1), and three equivalent O(4) atoms. The Tb(1)-O(3) bond length is 2.36 Å. Both Tb(1)-O(1) bond lengths are 2.32 Å. There are two shorter (2.31 Å) and one longer (2.34 Å) Tb(1)-O(4) bond length. In the second Tb site, Tb(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form TbO6 octahedra that share corners with two equivalent Tb(2)O6 octahedra, corners with four equivalent Ti(1)O6 octahedra, and edges with two equivalent Tb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-65°. There is one shorter (2.22 Å) and one longer (2.24 Å) Tb(2)-O(1) bond length. Both Tb(2)-O(3) bond lengths are 2.31 Å. Both Tb(2)-O(5) bond lengths are 2.38 Å. Ti(1) is bonded to one O(3), one O(4), one O(5), and three equivalent O(2) atoms to form distorted TiO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra, corners with four equivalent Tb(2)O6 octahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 35-64°. The Ti(1)-O(3) bond length is 2.05 Å. The Ti(1)-O(4) bond length is 2.01 Å. The Ti(1)-O(5) bond length is 1.86 Å. There are two shorter (1.91 Å) and one longer (2.47 Å) Ti(1)-O(2) bond length. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Tb(1) and two equivalent Tb(2) atoms to form OTb4 tetrahedra that share corners with two equivalent O(3)Tb3Ti tetrahedra, corners with four equivalent O(4)Tb3Ti tetrahedra, corners with four equivalent O(1)Tb4 tetrahedra,  an edgeedge with one O(4)Tb3Ti tetrahedra, and edges with two equivalent O(3)Tb3Ti tetrahedra. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to three equivalent Ti(1) atoms. In the third O site, O(3) is bonded to one Tb(1), two equivalent Tb(2), and one Ti(1) atom to form OTb3Ti tetrahedra that share corners with two equivalent O(3)Tb3Ti tetrahedra, corners with two equivalent O(1)Tb4 tetrahedra, corners with four equivalent O(4)Tb3Ti tetrahedra, and edges with two equivalent O(1)Tb4 tetrahedra. In the fourth O site, O(4) is bonded to three equivalent Tb(1) and one Ti(1) atom to form OTb3Ti tetrahedra that share corners with two equivalent O(4)Tb3Ti tetrahedra, corners with four equivalent O(3)Tb3Ti tetrahedra, corners with four equivalent O(1)Tb4 tetrahedra,  an edgeedge with one O(1)Tb4 tetrahedra, and edges with two equivalent O(4)Tb3Ti tetrahedra. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Tb(2) and one Ti(1) atom.