Na4Ti7O16 crystallizes in the monoclinic Pm space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(10), one O(2), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(2), one O(9), two equivalent O(4), and two equivalent O(7) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(2), one O(4), one O(7), one O(8), and one O(9) atom. There are five inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(11), one O(6), two equivalent O(12), and two equivalent O(3) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 46-48°. In the second Ti site, Ti(2) is bonded to one O(10), one O(5), two equivalent O(12), and two equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 48-53°. In the third Ti site, Ti(3) is bonded in a 6-coordinate geometry to one O(1), one O(8), two equivalent O(4), and two equivalent O(7) atoms. In the fourth Ti site, Ti(4) is bonded to one O(12), one O(4), one O(5), one O(6), one O(8), and one O(9) atom to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 46-53°. In the fifth Ti site, Ti(5) is bonded to one O(1), one O(10), one O(11), one O(2), one O(3), and one O(7) atom to form edge-sharing TiO6 octahedra. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ti(3) and two equivalent Ti(5) atoms. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), two equivalent Na(3), and two equivalent Ti(5) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Na(1), one Ti(1), one Ti(2), and one Ti(5) atom. In the fourth O site, O(4) is bonded to one Na(2), one Na(3), one Ti(3), and one Ti(4) atom to form distorted ONa2Ti2 trigonal pyramids that share  a cornercorner with one O(8)Na2Ti3 square pyramid,  a cornercorner with one O(9)Na3Ti2 square pyramid, corners with two equivalent O(4)Na2Ti2 trigonal pyramids,  an edgeedge with one O(8)Na2Ti3 square pyramid, and  an edgeedge with one O(9)Na3Ti2 square pyramid. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ti(2) and two equivalent Ti(4) atoms. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ti(1) and two equivalent Ti(4) atoms. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Na(2), one Na(3), one Ti(3), and one Ti(5) atom. In the eighth O site, O(8) is bonded to two equivalent Na(3), one Ti(3), and two equivalent Ti(4) atoms to form ONa2Ti3 square pyramids that share corners with two equivalent O(4)Na2Ti2 trigonal pyramids, edges with two equivalent O(9)Na3Ti2 square pyramids, and edges with two equivalent O(4)Na2Ti2 trigonal pyramids. In the ninth O site, O(9) is bonded to one Na(2), two equivalent Na(3), and two equivalent Ti(4) atoms to form ONa3Ti2 square pyramids that share corners with two equivalent O(4)Na2Ti2 trigonal pyramids, edges with two equivalent O(8)Na2Ti3 square pyramids, and edges with two equivalent O(4)Na2Ti2 trigonal pyramids. In the tenth O site, O(10) is bonded in a tetrahedral geometry to one Na(1), one Ti(2), and two equivalent Ti(5) atoms. In the eleventh O site, O(11) is bonded in a trigonal non-coplanar geometry to one Ti(1) and two equivalent Ti(5) atoms. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Ti(1), one Ti(2), and one Ti(4) atom.
Na4Ti7O16 crystallizes in the monoclinic Pm space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(10), one O(2), and two equivalent O(3) atoms. The Na(1)-O(10) bond length is 2.11 Å. The Na(1)-O(2) bond length is 2.46 Å. Both Na(1)-O(3) bond lengths are 2.23 Å. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(2), one O(9), two equivalent O(4), and two equivalent O(7) atoms. The Na(2)-O(2) bond length is 2.28 Å. The Na(2)-O(9) bond length is 2.41 Å. Both Na(2)-O(4) bond lengths are 2.20 Å. Both Na(2)-O(7) bond lengths are 2.23 Å. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(2), one O(4), one O(7), one O(8), and one O(9) atom. The Na(3)-O(2) bond length is 2.78 Å. The Na(3)-O(4) bond length is 2.14 Å. The Na(3)-O(7) bond length is 2.37 Å. The Na(3)-O(8) bond length is 2.27 Å. The Na(3)-O(9) bond length is 2.30 Å. There are five inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(11), one O(6), two equivalent O(12), and two equivalent O(3) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 46-48°. The Ti(1)-O(11) bond length is 1.97 Å. The Ti(1)-O(6) bond length is 2.02 Å. Both Ti(1)-O(12) bond lengths are 2.08 Å. Both Ti(1)-O(3) bond lengths are 1.92 Å. In the second Ti site, Ti(2) is bonded to one O(10), one O(5), two equivalent O(12), and two equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 48-53°. The Ti(2)-O(10) bond length is 2.08 Å. The Ti(2)-O(5) bond length is 2.00 Å. Both Ti(2)-O(12) bond lengths are 1.90 Å. Both Ti(2)-O(3) bond lengths are 2.10 Å. In the third Ti site, Ti(3) is bonded in a 6-coordinate geometry to one O(1), one O(8), two equivalent O(4), and two equivalent O(7) atoms. The Ti(3)-O(1) bond length is 1.93 Å. The Ti(3)-O(8) bond length is 2.34 Å. Both Ti(3)-O(4) bond lengths are 1.93 Å. Both Ti(3)-O(7) bond lengths are 2.01 Å. In the fourth Ti site, Ti(4) is bonded to one O(12), one O(4), one O(5), one O(6), one O(8), and one O(9) atom to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 46-53°. The Ti(4)-O(12) bond length is 2.20 Å. The Ti(4)-O(4) bond length is 1.88 Å. The Ti(4)-O(5) bond length is 2.06 Å. The Ti(4)-O(6) bond length is 2.01 Å. The Ti(4)-O(8) bond length is 1.99 Å. The Ti(4)-O(9) bond length is 1.93 Å. In the fifth Ti site, Ti(5) is bonded to one O(1), one O(10), one O(11), one O(2), one O(3), and one O(7) atom to form edge-sharing TiO6 octahedra. The Ti(5)-O(1) bond length is 2.18 Å. The Ti(5)-O(10) bond length is 1.97 Å. The Ti(5)-O(11) bond length is 1.97 Å. The Ti(5)-O(2) bond length is 1.96 Å. The Ti(5)-O(3) bond length is 2.07 Å. The Ti(5)-O(7) bond length is 1.86 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ti(3) and two equivalent Ti(5) atoms. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), two equivalent Na(3), and two equivalent Ti(5) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Na(1), one Ti(1), one Ti(2), and one Ti(5) atom. In the fourth O site, O(4) is bonded to one Na(2), one Na(3), one Ti(3), and one Ti(4) atom to form distorted ONa2Ti2 trigonal pyramids that share  a cornercorner with one O(8)Na2Ti3 square pyramid,  a cornercorner with one O(9)Na3Ti2 square pyramid, corners with two equivalent O(4)Na2Ti2 trigonal pyramids,  an edgeedge with one O(8)Na2Ti3 square pyramid, and  an edgeedge with one O(9)Na3Ti2 square pyramid. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ti(2) and two equivalent Ti(4) atoms. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ti(1) and two equivalent Ti(4) atoms. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Na(2), one Na(3), one Ti(3), and one Ti(5) atom. In the eighth O site, O(8) is bonded to two equivalent Na(3), one Ti(3), and two equivalent Ti(4) atoms to form ONa2Ti3 square pyramids that share corners with two equivalent O(4)Na2Ti2 trigonal pyramids, edges with two equivalent O(9)Na3Ti2 square pyramids, and edges with two equivalent O(4)Na2Ti2 trigonal pyramids. In the ninth O site, O(9) is bonded to one Na(2), two equivalent Na(3), and two equivalent Ti(4) atoms to form ONa3Ti2 square pyramids that share corners with two equivalent O(4)Na2Ti2 trigonal pyramids, edges with two equivalent O(8)Na2Ti3 square pyramids, and edges with two equivalent O(4)Na2Ti2 trigonal pyramids. In the tenth O site, O(10) is bonded in a tetrahedral geometry to one Na(1), one Ti(2), and two equivalent Ti(5) atoms. In the eleventh O site, O(11) is bonded in a trigonal non-coplanar geometry to one Ti(1) and two equivalent Ti(5) atoms. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Ti(1), one Ti(2), and one Ti(4) atom.