Sm2TiO5 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to one O(1), one O(3), one O(4), two equivalent O(2), and two equivalent O(5) atoms to form distorted SmO7 hexagonal pyramids that share corners with two equivalent Sm(2)O7 hexagonal pyramids, corners with three equivalent Ti(1)O5 trigonal bipyramids, edges with two equivalent Sm(1)O7 hexagonal pyramids, edges with three equivalent Sm(2)O7 hexagonal pyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. In the second Sm site, Sm(2) is bonded to one O(4), one O(5), two equivalent O(3), and three equivalent O(1) atoms to form distorted SmO7 hexagonal pyramids that share corners with two equivalent Sm(1)O7 hexagonal pyramids,  a cornercorner with one Ti(1)O5 trigonal bipyramid, edges with three equivalent Sm(1)O7 hexagonal pyramids, edges with four equivalent Sm(2)O7 hexagonal pyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. Ti(1) is bonded to one O(2), one O(3), one O(5), and two equivalent O(4) atoms to form distorted TiO5 trigonal bipyramids that share  a cornercorner with one Sm(2)O7 hexagonal pyramid, corners with three equivalent Sm(1)O7 hexagonal pyramids, corners with two equivalent Ti(1)O5 trigonal bipyramids, edges with two equivalent Sm(1)O7 hexagonal pyramids, and edges with two equivalent Sm(2)O7 hexagonal pyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Sm(1) and three equivalent Sm(2) atoms to form OSm4 tetrahedra that share corners with two equivalent O(4)Sm2Ti2 tetrahedra, corners with two equivalent O(1)Sm4 tetrahedra, corners with five equivalent O(3)Sm3Ti tetrahedra, corners with five equivalent O(5)Sm3Ti tetrahedra,  an edgeedge with one O(4)Sm2Ti2 tetrahedra,  an edgeedge with one O(3)Sm3Ti tetrahedra, and edges with two equivalent O(1)Sm4 tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Sm(1) and one Ti(1) atom. In the third O site, O(3) is bonded to one Sm(1), two equivalent Sm(2), and one Ti(1) atom to form distorted OSm3Ti tetrahedra that share  a cornercorner with one O(4)Sm2Ti2 tetrahedra,  a cornercorner with one O(5)Sm3Ti tetrahedra, corners with two equivalent O(3)Sm3Ti tetrahedra, corners with five equivalent O(1)Sm4 tetrahedra,  an edgeedge with one O(1)Sm4 tetrahedra, edges with two equivalent O(4)Sm2Ti2 tetrahedra, and edges with two equivalent O(5)Sm3Ti tetrahedra. In the fourth O site, O(4) is bonded to one Sm(1), one Sm(2), and two equivalent Ti(1) atoms to form distorted OSm2Ti2 tetrahedra that share  a cornercorner with one O(3)Sm3Ti tetrahedra,  a cornercorner with one O(5)Sm3Ti tetrahedra, corners with two equivalent O(4)Sm2Ti2 tetrahedra, corners with two equivalent O(1)Sm4 tetrahedra,  an edgeedge with one O(1)Sm4 tetrahedra, edges with two equivalent O(3)Sm3Ti tetrahedra, and edges with two equivalent O(5)Sm3Ti tetrahedra. In the fifth O site, O(5) is bonded to one Sm(2), two equivalent Sm(1), and one Ti(1) atom to form OSm3Ti tetrahedra that share  a cornercorner with one O(4)Sm2Ti2 tetrahedra,  a cornercorner with one O(3)Sm3Ti tetrahedra, corners with two equivalent O(5)Sm3Ti tetrahedra, corners with five equivalent O(1)Sm4 tetrahedra, edges with two equivalent O(4)Sm2Ti2 tetrahedra, and edges with two equivalent O(3)Sm3Ti tetrahedra.
Sm2TiO5 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to one O(1), one O(3), one O(4), two equivalent O(2), and two equivalent O(5) atoms to form distorted SmO7 hexagonal pyramids that share corners with two equivalent Sm(2)O7 hexagonal pyramids, corners with three equivalent Ti(1)O5 trigonal bipyramids, edges with two equivalent Sm(1)O7 hexagonal pyramids, edges with three equivalent Sm(2)O7 hexagonal pyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. The Sm(1)-O(1) bond length is 2.34 Å. The Sm(1)-O(3) bond length is 2.41 Å. The Sm(1)-O(4) bond length is 2.45 Å. Both Sm(1)-O(2) bond lengths are 2.42 Å. Both Sm(1)-O(5) bond lengths are 2.33 Å. In the second Sm site, Sm(2) is bonded to one O(4), one O(5), two equivalent O(3), and three equivalent O(1) atoms to form distorted SmO7 hexagonal pyramids that share corners with two equivalent Sm(1)O7 hexagonal pyramids,  a cornercorner with one Ti(1)O5 trigonal bipyramid, edges with three equivalent Sm(1)O7 hexagonal pyramids, edges with four equivalent Sm(2)O7 hexagonal pyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. The Sm(2)-O(4) bond length is 2.41 Å. The Sm(2)-O(5) bond length is 2.39 Å. Both Sm(2)-O(3) bond lengths are 2.41 Å. There is one shorter (2.39 Å) and two longer (2.40 Å) Sm(2)-O(1) bond lengths. Ti(1) is bonded to one O(2), one O(3), one O(5), and two equivalent O(4) atoms to form distorted TiO5 trigonal bipyramids that share  a cornercorner with one Sm(2)O7 hexagonal pyramid, corners with three equivalent Sm(1)O7 hexagonal pyramids, corners with two equivalent Ti(1)O5 trigonal bipyramids, edges with two equivalent Sm(1)O7 hexagonal pyramids, and edges with two equivalent Sm(2)O7 hexagonal pyramids. The Ti(1)-O(2) bond length is 1.78 Å. The Ti(1)-O(3) bond length is 1.89 Å. The Ti(1)-O(5) bond length is 1.91 Å. Both Ti(1)-O(4) bond lengths are 1.98 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Sm(1) and three equivalent Sm(2) atoms to form OSm4 tetrahedra that share corners with two equivalent O(4)Sm2Ti2 tetrahedra, corners with two equivalent O(1)Sm4 tetrahedra, corners with five equivalent O(3)Sm3Ti tetrahedra, corners with five equivalent O(5)Sm3Ti tetrahedra,  an edgeedge with one O(4)Sm2Ti2 tetrahedra,  an edgeedge with one O(3)Sm3Ti tetrahedra, and edges with two equivalent O(1)Sm4 tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Sm(1) and one Ti(1) atom. In the third O site, O(3) is bonded to one Sm(1), two equivalent Sm(2), and one Ti(1) atom to form distorted OSm3Ti tetrahedra that share  a cornercorner with one O(4)Sm2Ti2 tetrahedra,  a cornercorner with one O(5)Sm3Ti tetrahedra, corners with two equivalent O(3)Sm3Ti tetrahedra, corners with five equivalent O(1)Sm4 tetrahedra,  an edgeedge with one O(1)Sm4 tetrahedra, edges with two equivalent O(4)Sm2Ti2 tetrahedra, and edges with two equivalent O(5)Sm3Ti tetrahedra. In the fourth O site, O(4) is bonded to one Sm(1), one Sm(2), and two equivalent Ti(1) atoms to form distorted OSm2Ti2 tetrahedra that share  a cornercorner with one O(3)Sm3Ti tetrahedra,  a cornercorner with one O(5)Sm3Ti tetrahedra, corners with two equivalent O(4)Sm2Ti2 tetrahedra, corners with two equivalent O(1)Sm4 tetrahedra,  an edgeedge with one O(1)Sm4 tetrahedra, edges with two equivalent O(3)Sm3Ti tetrahedra, and edges with two equivalent O(5)Sm3Ti tetrahedra. In the fifth O site, O(5) is bonded to one Sm(2), two equivalent Sm(1), and one Ti(1) atom to form OSm3Ti tetrahedra that share  a cornercorner with one O(4)Sm2Ti2 tetrahedra,  a cornercorner with one O(3)Sm3Ti tetrahedra, corners with two equivalent O(5)Sm3Ti tetrahedra, corners with five equivalent O(1)Sm4 tetrahedra, edges with two equivalent O(4)Sm2Ti2 tetrahedra, and edges with two equivalent O(3)Sm3Ti tetrahedra.