PbTi3O7 crystallizes in the monoclinic P2_1/m space group. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(4), one O(6), one O(7), and three equivalent O(1) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra, corners with five equivalent Pb(1)O5 square pyramids,  an edgeedge with one Ti(3)O6 octahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 22-23°. In the second Ti site, Ti(2) is bonded to one O(2), one O(5), one O(6), and three equivalent O(3) atoms to form a mixture of distorted edge and corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 14-31°. In the third Ti site, Ti(3) is bonded to one O(3), one O(5), one O(6), one O(7), and two equivalent O(2) atoms to form distorted TiO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra, corners with two equivalent Ti(3)O6 octahedra, corners with two equivalent Pb(1)O5 square pyramids,  an edgeedge with one Ti(1)O6 octahedra, and edges with three equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-24°. Pb(1) is bonded to two equivalent O(7) and three equivalent O(4) atoms to form distorted PbO5 square pyramids that share corners with two equivalent Ti(3)O6 octahedra, corners with five equivalent Ti(1)O6 octahedra, and edges with four equivalent Pb(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 54-78°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to three equivalent Ti(1) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ti(2) and two equivalent Ti(3) atoms. In the third O site, O(3) is bonded to one Ti(3) and three equivalent Ti(2) atoms to form a mixture of distorted edge and corner-sharing OTi4 trigonal pyramids. In the fourth O site, O(4) is bonded to one Ti(1) and three equivalent Pb(1) atoms to form a mixture of distorted edge and corner-sharing OTiPb3 tetrahedra. In the fifth O site, O(5) is bonded in a linear geometry to one Ti(2) and one Ti(3) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Ti(1), one Ti(2), and one Ti(3) atom. In the seventh O site, O(7) is bonded in a distorted water-like geometry to one Ti(1), one Ti(3), and two equivalent Pb(1) atoms.
PbTi3O7 crystallizes in the monoclinic P2_1/m space group. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(4), one O(6), one O(7), and three equivalent O(1) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra, corners with five equivalent Pb(1)O5 square pyramids,  an edgeedge with one Ti(3)O6 octahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 22-23°. The Ti(1)-O(4) bond length is 1.86 Å. The Ti(1)-O(6) bond length is 2.00 Å. The Ti(1)-O(7) bond length is 2.04 Å. There are two shorter (1.94 Å) and one longer (2.02 Å) Ti(1)-O(1) bond length. In the second Ti site, Ti(2) is bonded to one O(2), one O(5), one O(6), and three equivalent O(3) atoms to form a mixture of distorted edge and corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 14-31°. The Ti(2)-O(2) bond length is 2.03 Å. The Ti(2)-O(5) bond length is 1.77 Å. The Ti(2)-O(6) bond length is 1.92 Å. There are two shorter (1.98 Å) and one longer (2.29 Å) Ti(2)-O(3) bond length. In the third Ti site, Ti(3) is bonded to one O(3), one O(5), one O(6), one O(7), and two equivalent O(2) atoms to form distorted TiO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra, corners with two equivalent Ti(3)O6 octahedra, corners with two equivalent Pb(1)O5 square pyramids,  an edgeedge with one Ti(1)O6 octahedra, and edges with three equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-24°. The Ti(3)-O(3) bond length is 2.11 Å. The Ti(3)-O(5) bond length is 1.95 Å. The Ti(3)-O(6) bond length is 2.07 Å. The Ti(3)-O(7) bond length is 1.82 Å. Both Ti(3)-O(2) bond lengths are 1.95 Å. Pb(1) is bonded to two equivalent O(7) and three equivalent O(4) atoms to form distorted PbO5 square pyramids that share corners with two equivalent Ti(3)O6 octahedra, corners with five equivalent Ti(1)O6 octahedra, and edges with four equivalent Pb(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 54-78°. Both Pb(1)-O(7) bond lengths are 2.58 Å. There is one shorter (2.34 Å) and two longer (2.48 Å) Pb(1)-O(4) bond lengths. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to three equivalent Ti(1) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ti(2) and two equivalent Ti(3) atoms. In the third O site, O(3) is bonded to one Ti(3) and three equivalent Ti(2) atoms to form a mixture of distorted edge and corner-sharing OTi4 trigonal pyramids. In the fourth O site, O(4) is bonded to one Ti(1) and three equivalent Pb(1) atoms to form a mixture of distorted edge and corner-sharing OTiPb3 tetrahedra. In the fifth O site, O(5) is bonded in a linear geometry to one Ti(2) and one Ti(3) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Ti(1), one Ti(2), and one Ti(3) atom. In the seventh O site, O(7) is bonded in a distorted water-like geometry to one Ti(1), one Ti(3), and two equivalent Pb(1) atoms.