Na2Ti6O13 crystallizes in the monoclinic C2/m space group. Na(1) is bonded in a 4-coordinate geometry to two equivalent O(3) and two equivalent O(7) atoms. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(3), one O(6), one O(7), and three equivalent O(4) atoms to form a mixture of distorted edge and corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 34°. In the second Ti site, Ti(2) is bonded to one O(1), one O(5), one O(6), one O(7), and two equivalent O(2) atoms to form a mixture of edge and corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-28°. In the third Ti site, Ti(3) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), and two equivalent O(6) atoms. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one Ti(2) and one Ti(3) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ti(3) and two equivalent Ti(2) atoms. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(1), one Ti(1), and one Ti(3) atom. In the fourth O site, O(4) is bonded to one Ti(3) and three equivalent Ti(1) atoms to form distorted OTi4 trigonal pyramids that share corners with three equivalent O(7)Na2Ti2 tetrahedra,  a cornercorner with one O(6)Ti4 trigonal pyramid, corners with two equivalent O(4)Ti4 trigonal pyramids, edges with two equivalent O(4)Ti4 trigonal pyramids, and edges with two equivalent O(6)Ti4 trigonal pyramids. In the fifth O site, O(5) is bonded in a linear geometry to two equivalent Ti(2) atoms. In the sixth O site, O(6) is bonded to one Ti(1), one Ti(2), and two equivalent Ti(3) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(4)Ti4 trigonal pyramid, corners with two equivalent O(6)Ti4 trigonal pyramids,  an edgeedge with one O(7)Na2Ti2 tetrahedra, and edges with two equivalent O(4)Ti4 trigonal pyramids. In the seventh O site, O(7) is bonded to two equivalent Na(1), one Ti(1), and one Ti(2) atom to form ONa2Ti2 tetrahedra that share corners with two equivalent O(7)Na2Ti2 tetrahedra, corners with three equivalent O(4)Ti4 trigonal pyramids, and  an edgeedge with one O(6)Ti4 trigonal pyramid.
Na2Ti6O13 crystallizes in the monoclinic C2/m space group. Na(1) is bonded in a 4-coordinate geometry to two equivalent O(3) and two equivalent O(7) atoms. Both Na(1)-O(3) bond lengths are 2.62 Å. Both Na(1)-O(7) bond lengths are 2.46 Å. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(3), one O(6), one O(7), and three equivalent O(4) atoms to form a mixture of distorted edge and corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 34°. The Ti(1)-O(3) bond length is 1.84 Å. The Ti(1)-O(6) bond length is 2.22 Å. The Ti(1)-O(7) bond length is 1.81 Å. There are two shorter (1.95 Å) and one longer (2.18 Å) Ti(1)-O(4) bond length. In the second Ti site, Ti(2) is bonded to one O(1), one O(5), one O(6), one O(7), and two equivalent O(2) atoms to form a mixture of edge and corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-28°. The Ti(2)-O(1) bond length is 1.93 Å. The Ti(2)-O(5) bond length is 1.82 Å. The Ti(2)-O(6) bond length is 2.18 Å. The Ti(2)-O(7) bond length is 2.03 Å. Both Ti(2)-O(2) bond lengths are 1.92 Å. In the third Ti site, Ti(3) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), and two equivalent O(6) atoms. The Ti(3)-O(1) bond length is 1.76 Å. The Ti(3)-O(2) bond length is 2.05 Å. The Ti(3)-O(3) bond length is 1.93 Å. The Ti(3)-O(4) bond length is 2.25 Å. Both Ti(3)-O(6) bond lengths are 1.94 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one Ti(2) and one Ti(3) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ti(3) and two equivalent Ti(2) atoms. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(1), one Ti(1), and one Ti(3) atom. In the fourth O site, O(4) is bonded to one Ti(3) and three equivalent Ti(1) atoms to form distorted OTi4 trigonal pyramids that share corners with three equivalent O(7)Na2Ti2 tetrahedra,  a cornercorner with one O(6)Ti4 trigonal pyramid, corners with two equivalent O(4)Ti4 trigonal pyramids, edges with two equivalent O(4)Ti4 trigonal pyramids, and edges with two equivalent O(6)Ti4 trigonal pyramids. In the fifth O site, O(5) is bonded in a linear geometry to two equivalent Ti(2) atoms. In the sixth O site, O(6) is bonded to one Ti(1), one Ti(2), and two equivalent Ti(3) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(4)Ti4 trigonal pyramid, corners with two equivalent O(6)Ti4 trigonal pyramids,  an edgeedge with one O(7)Na2Ti2 tetrahedra, and edges with two equivalent O(4)Ti4 trigonal pyramids. In the seventh O site, O(7) is bonded to two equivalent Na(1), one Ti(1), and one Ti(2) atom to form ONa2Ti2 tetrahedra that share corners with two equivalent O(7)Na2Ti2 tetrahedra, corners with three equivalent O(4)Ti4 trigonal pyramids, and  an edgeedge with one O(6)Ti4 trigonal pyramid.