Na3Ti6O13 crystallizes in the monoclinic C2/m space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 7-coordinate geometry to one O(5), two equivalent O(2), two equivalent O(6), and two equivalent O(7) atoms. In the second Na site, Na(2) is bonded in a square co-planar geometry to four equivalent O(4) atoms. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(6), one O(7), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-23°. In the second Ti site, Ti(2) is bonded to one O(1), one O(2), one O(4), and three equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 31°. In the third Ti site, Ti(3) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(6), and two equivalent O(1) atoms. There are seven inequivalent O sites. In the first O site, O(1) 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(7)Na4Ti2 octahedra,  a cornercorner with one O(3)Ti4 trigonal pyramid, corners with two equivalent O(1)Ti4 trigonal pyramids, and edges with two equivalent O(3)Ti4 trigonal pyramids. The corner-sharing octahedral tilt angles are 16°. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Ti(1), and one Ti(2) atom. 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 corner and edge-sharing OTi4 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(2), one Ti(2), and one Ti(3) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Na(1), one Ti(3), and two equivalent Ti(1) atoms. In the sixth O site, O(6) 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 seventh O site, O(7) is bonded to four equivalent Na(1) and two equivalent Ti(1) atoms to form distorted ONa4Ti2 octahedra that share corners with two equivalent O(1)Ti4 trigonal pyramids and edges with two equivalent O(7)Na4Ti2 octahedra.
Na3Ti6O13 crystallizes in the monoclinic C2/m space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 7-coordinate geometry to one O(5), two equivalent O(2), two equivalent O(6), and two equivalent O(7) atoms. The Na(1)-O(5) bond length is 2.84 Å. Both Na(1)-O(2) bond lengths are 2.53 Å. Both Na(1)-O(6) bond lengths are 2.67 Å. Both Na(1)-O(7) bond lengths are 2.65 Å. In the second Na site, Na(2) is bonded in a square co-planar geometry to four equivalent O(4) atoms. All Na(2)-O(4) bond lengths are 2.64 Å. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(6), one O(7), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-23°. The Ti(1)-O(1) bond length is 2.16 Å. The Ti(1)-O(2) bond length is 2.21 Å. The Ti(1)-O(6) bond length is 1.97 Å. The Ti(1)-O(7) bond length is 1.87 Å. Both Ti(1)-O(5) bond lengths are 1.93 Å. In the second Ti site, Ti(2) is bonded to one O(1), one O(2), one O(4), and three equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 31°. The Ti(2)-O(1) bond length is 2.24 Å. The Ti(2)-O(2) bond length is 1.79 Å. The Ti(2)-O(4) bond length is 1.88 Å. There are two shorter (1.96 Å) and one longer (2.20 Å) Ti(2)-O(3) bond length. In the third Ti site, Ti(3) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(6), and two equivalent O(1) atoms. The Ti(3)-O(3) bond length is 2.31 Å. The Ti(3)-O(4) bond length is 1.95 Å. The Ti(3)-O(5) bond length is 2.12 Å. The Ti(3)-O(6) bond length is 1.79 Å. Both Ti(3)-O(1) bond lengths are 1.96 Å. There are seven inequivalent O sites. In the first O site, O(1) 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(7)Na4Ti2 octahedra,  a cornercorner with one O(3)Ti4 trigonal pyramid, corners with two equivalent O(1)Ti4 trigonal pyramids, and edges with two equivalent O(3)Ti4 trigonal pyramids. The corner-sharing octahedral tilt angles are 16°. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Ti(1), and one Ti(2) atom. 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 corner and edge-sharing OTi4 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(2), one Ti(2), and one Ti(3) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Na(1), one Ti(3), and two equivalent Ti(1) atoms. In the sixth O site, O(6) 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 seventh O site, O(7) is bonded to four equivalent Na(1) and two equivalent Ti(1) atoms to form distorted ONa4Ti2 octahedra that share corners with two equivalent O(1)Ti4 trigonal pyramids and edges with two equivalent O(7)Na4Ti2 octahedra.