Na2Ti7O15 crystallizes in the monoclinic Cm space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a square co-planar geometry to two equivalent O(29) and two equivalent O(30) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(12), two equivalent O(14), and two equivalent O(18) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to two equivalent O(3) and two equivalent O(5) atoms. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to two equivalent O(4) and two equivalent O(6) atoms. There are fourteen inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(17), one O(19), one O(21), one O(29), and two equivalent O(1) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 33°. In the second Ti site, Ti(2) is bonded to one O(18), one O(20), one O(22), one O(30), and two equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 34°. In the third Ti site, Ti(3) is bonded to one O(13), one O(15), one O(23), one O(5), and two equivalent O(27) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 7-28°. In the fourth Ti site, Ti(4) is bonded to one O(14), one O(16), one O(24), one O(6), and two equivalent O(28) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 5-25°. In the fifth Ti site, Ti(5) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(13), one O(25), and two equivalent O(19) atoms. In the sixth Ti site, Ti(6) is bonded in a 6-coordinate geometry to one O(12), one O(14), one O(2), one O(26), and two equivalent O(20) atoms. In the seventh Ti site, Ti(7) is bonded in a 6-coordinate geometry to one O(27), one O(3), one O(7), one O(9), and two equivalent O(15) atoms. In the eighth Ti site, Ti(8) is bonded to one O(10), one O(28), one O(4), one O(8), and two equivalent O(16) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 8-31°. In the ninth Ti site, Ti(9) is bonded to one O(1), one O(11), one O(22), one O(30), and two equivalent O(21) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 32°. In the tenth Ti site, Ti(10) is bonded to one O(12), one O(2), one O(21), one O(29), and two equivalent O(22) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 30°. In the eleventh Ti site, Ti(11) is bonded to one O(10), one O(15), one O(4), one O(5), and two equivalent O(9) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 34°. In the twelfth Ti site, Ti(12) is bonded to one O(16), one O(3), one O(6), one O(9), and two equivalent O(10) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 33°. In the thirteenth Ti site, Ti(13) is bonded to one O(17), one O(19), one O(23), one O(7), and two equivalent O(25) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 7-31°. In the fourteenth Ti site, Ti(14) is bonded to one O(18), one O(20), one O(24), one O(8), and two equivalent O(26) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 5-27°. There are thirty inequivalent O sites. In the first O site, O(1) is bonded to one Ti(5), one Ti(9), and two equivalent Ti(1) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(30)Na2Ti2 tetrahedra, corners with two equivalent O(29)Na2Ti2 tetrahedra,  a cornercorner with one O(22)Ti4 trigonal pyramid, corners with two equivalent O(1)Ti4 trigonal pyramids, edges with two equivalent O(19)Ti4 trigonal pyramids, and edges with two equivalent O(21)Ti4 trigonal pyramids. In the second O site, O(2) is bonded to one Ti(10), one Ti(6), and two equivalent Ti(2) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(29)Na2Ti2 tetrahedra, corners with two equivalent O(30)Na2Ti2 tetrahedra,  a cornercorner with one O(21)Ti4 trigonal pyramid, corners with two equivalent O(2)Ti4 trigonal pyramids, edges with two equivalent O(20)Ti4 trigonal pyramids, and edges with two equivalent O(22)Ti4 trigonal pyramids. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(3), one Ti(12), and one Ti(7) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(4), one Ti(11), and one Ti(8) atom. In the fifth O site, O(5) is bonded to two equivalent Na(3), one Ti(11), and one Ti(3) atom to form distorted ONa2Ti2 tetrahedra that share corners with two equivalent O(5)Na2Ti2 tetrahedra,  a cornercorner with one O(10)Ti4 trigonal pyramid, corners with two equivalent O(9)Ti4 trigonal pyramids, and  an edgeedge with one O(15)Ti4 trigonal pyramid. In the sixth O site, O(6) is bonded to two equivalent Na(4), one Ti(12), and one Ti(4) atom to form distorted ONa2Ti2 tetrahedra that share corners with two equivalent O(6)Na2Ti2 tetrahedra,  a cornercorner with one O(9)Ti4 trigonal pyramid, corners with two equivalent O(10)Ti4 trigonal pyramids, and  an edgeedge with one O(16)Ti4 trigonal pyramid. In the seventh O site, O(7) is bonded in a linear geometry to one Ti(13) and one Ti(7) atom. In the eighth O site, O(8) is bonded in a linear geometry to one Ti(14) and one Ti(8) atom. In the ninth O site, O(9) is bonded to one Ti(12), one Ti(7), and two equivalent Ti(11) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(6)Na2Ti2 tetrahedra, corners with two equivalent O(5)Na2Ti2 tetrahedra,  a cornercorner with one O(16)Ti4 trigonal pyramid, corners with two equivalent O(9)Ti4 trigonal pyramids, edges with two equivalent O(10)Ti4 trigonal pyramids, and edges with two equivalent O(15)Ti4 trigonal pyramids. In the tenth O site, O(10) is bonded to one Ti(11), one Ti(8), and two equivalent Ti(12) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(5)Na2Ti2 tetrahedra, corners with two equivalent O(6)Na2Ti2 tetrahedra,  a cornercorner with one O(15)Ti4 trigonal pyramid, corners with two equivalent O(10)Ti4 trigonal pyramids, edges with two equivalent O(16)Ti4 trigonal pyramids, and edges with two equivalent O(9)Ti4 trigonal pyramids. In the eleventh O site, O(11) is bonded in a water-like geometry to one Ti(5) and one Ti(9) atom. In the twelfth O site, O(12) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(2), one Ti(10), and one Ti(6) atom. In the thirteenth O site, O(13) is bonded in a linear geometry to one Ti(3) and one Ti(5) atom. In the fourteenth O site, O(14) is bonded in a distorted linear geometry to two equivalent Na(2), one Ti(4), and one Ti(6) atom. In the fifteenth O site, O(15) is bonded to one Ti(11), one Ti(3), and two equivalent Ti(7) atoms to form OTi4 trigonal pyramids that share  a cornercorner with one O(10)Ti4 trigonal pyramid, corners with two equivalent O(15)Ti4 trigonal pyramids,  an edgeedge with one O(5)Na2Ti2 tetrahedra, and edges with two equivalent O(9)Ti4 trigonal pyramids. In the sixteenth O site, O(16) is bonded to one Ti(12), one Ti(4), and two equivalent Ti(8) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(9)Ti4 trigonal pyramid, corners with two equivalent O(16)Ti4 trigonal pyramids,  an edgeedge with one O(6)Na2Ti2 tetrahedra, and edges with two equivalent O(10)Ti4 trigonal pyramids. In the seventeenth O site, O(17) is bonded in a water-like geometry to one Ti(1) and one Ti(13) atom. In the eighteenth O site, O(18) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(2), one Ti(14), and one Ti(2) atom. In the nineteenth O site, O(19) is bonded to one Ti(1), one Ti(13), and two equivalent Ti(5) atoms to form OTi4 trigonal pyramids that share  a cornercorner with one O(29)Na2Ti2 tetrahedra,  a cornercorner with one O(21)Ti4 trigonal pyramid, corners with two equivalent O(19)Ti4 trigonal pyramids, and edges with two equivalent O(1)Ti4 trigonal pyramids. In the twentieth O site, O(20) is bonded to one Ti(14), one Ti(2), and two equivalent Ti(6) atoms to form OTi4 trigonal pyramids that share  a cornercorner with one O(30)Na2Ti2 tetrahedra,  a cornercorner with one O(22)Ti4 trigonal pyramid, corners with two equivalent O(20)Ti4 trigonal pyramids, and edges with two equivalent O(2)Ti4 trigonal pyramids. In the twenty-first O site, O(21) is bonded to one Ti(1), one Ti(10), and two equivalent Ti(9) atoms to form distorted OTi4 trigonal pyramids that share corners with two equivalent O(30)Na2Ti2 tetrahedra,  a cornercorner with one O(19)Ti4 trigonal pyramid,  a cornercorner with one O(2)Ti4 trigonal pyramid, corners with two equivalent O(21)Ti4 trigonal pyramids,  an edgeedge with one O(29)Na2Ti2 tetrahedra, edges with two equivalent O(1)Ti4 trigonal pyramids, and edges with two equivalent O(22)Ti4 trigonal pyramids. In the twenty-second O site, O(22) is bonded to one Ti(2), one Ti(9), and two equivalent Ti(10) atoms to form distorted OTi4 trigonal pyramids that share corners with two equivalent O(29)Na2Ti2 tetrahedra,  a cornercorner with one O(1)Ti4 trigonal pyramid,  a cornercorner with one O(20)Ti4 trigonal pyramid, corners with two equivalent O(22)Ti4 trigonal pyramids,  an edgeedge with one O(30)Na2Ti2 tetrahedra, edges with two equivalent O(2)Ti4 trigonal pyramids, and edges with two equivalent O(21)Ti4 trigonal pyramids. In the twenty-third O site, O(23) is bonded in a linear geometry to one Ti(13) and one Ti(3) atom. In the twenty-fourth O site, O(24) is bonded in a linear geometry to one Ti(14) and one Ti(4) atom. In the twenty-fifth O site, O(25) is bonded in a distorted trigonal non-coplanar geometry to one Ti(5) and two equivalent Ti(13) atoms. In the twenty-sixth O site, O(26) is bonded in a distorted T-shaped geometry to one Ti(6) and two equivalent Ti(14) atoms. In the twenty-seventh O site, O(27) is bonded in a distorted T-shaped geometry to one Ti(7) and two equivalent Ti(3) atoms. In the twenty-eighth O site, O(28) is bonded in a distorted T-shaped geometry to one Ti(8) and two equivalent Ti(4) atoms. In the twenty-ninth O site, O(29) is bonded to two equivalent Na(1), one Ti(1), and one Ti(10) atom to form ONa2Ti2 tetrahedra that share corners with two equivalent O(29)Na2Ti2 tetrahedra, corners with two equivalent O(30)Na2Ti2 tetrahedra,  a cornercorner with one O(19)Ti4 trigonal pyramid,  a cornercorner with one O(2)Ti4 trigonal pyramid, corners with two equivalent O(1)Ti4 trigonal pyramids, corners with two equivalent O(22)Ti4 trigonal pyramids,  an edgeedge with one O(30)Na2Ti2 tetrahedra, and  an edgeedge with one O(21)Ti4 trigonal pyramid. In the thirtieth O site, O(30) is bonded to two equivalent Na(1), one Ti(2), and one Ti(9) atom to form ONa2Ti2 tetrahedra that share corners with two equivalent O(29)Na2Ti2 tetrahedra, corners with two equivalent O(30)Na2Ti2 tetrahedra,  a cornercorner with one O(1)Ti4 trigonal pyramid,  a cornercorner with one O(20)Ti4 trigonal pyramid, corners with two equivalent O(2)Ti4 trigonal pyramids, corners with two equivalent O(21)Ti4 trigonal pyramids,  an edgeedge with one O(29)Na2Ti2 tetrahedra, and  an edgeedge with one O(22)Ti4 trigonal pyramid.
Na2Ti7O15 crystallizes in the monoclinic Cm space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a square co-planar geometry to two equivalent O(29) and two equivalent O(30) atoms. Both Na(1)-O(29) bond lengths are 2.46 Å. Both Na(1)-O(30) bond lengths are 2.48 Å. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(12), two equivalent O(14), and two equivalent O(18) atoms. Both Na(2)-O(12) bond lengths are 2.75 Å. Both Na(2)-O(14) bond lengths are 2.85 Å. Both Na(2)-O(18) bond lengths are 2.58 Å. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to two equivalent O(3) and two equivalent O(5) atoms. Both Na(3)-O(3) bond lengths are 2.66 Å. Both Na(3)-O(5) bond lengths are 2.52 Å. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to two equivalent O(4) and two equivalent O(6) atoms. Both Na(4)-O(4) bond lengths are 2.63 Å. Both Na(4)-O(6) bond lengths are 2.52 Å. There are fourteen inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(17), one O(19), one O(21), one O(29), and two equivalent O(1) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 33°. The Ti(1)-O(17) bond length is 1.75 Å. The Ti(1)-O(19) bond length is 2.14 Å. The Ti(1)-O(21) bond length is 2.30 Å. The Ti(1)-O(29) bond length is 1.95 Å. Both Ti(1)-O(1) bond lengths are 1.97 Å. In the second Ti site, Ti(2) is bonded to one O(18), one O(20), one O(22), one O(30), and two equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 34°. The Ti(2)-O(18) bond length is 1.79 Å. The Ti(2)-O(20) bond length is 2.21 Å. The Ti(2)-O(22) bond length is 2.27 Å. The Ti(2)-O(30) bond length is 1.89 Å. Both Ti(2)-O(2) bond lengths are 1.97 Å. In the third Ti site, Ti(3) is bonded to one O(13), one O(15), one O(23), one O(5), and two equivalent O(27) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 7-28°. The Ti(3)-O(13) bond length is 1.90 Å. The Ti(3)-O(15) bond length is 2.22 Å. The Ti(3)-O(23) bond length is 1.83 Å. The Ti(3)-O(5) bond length is 2.12 Å. Both Ti(3)-O(27) bond lengths are 1.94 Å. In the fourth Ti site, Ti(4) is bonded to one O(14), one O(16), one O(24), one O(6), and two equivalent O(28) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 5-25°. The Ti(4)-O(14) bond length is 2.02 Å. The Ti(4)-O(16) bond length is 2.15 Å. The Ti(4)-O(24) bond length is 1.86 Å. The Ti(4)-O(6) bond length is 1.98 Å. Both Ti(4)-O(28) bond lengths are 1.93 Å. In the fifth Ti site, Ti(5) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(13), one O(25), and two equivalent O(19) atoms. The Ti(5)-O(1) bond length is 2.38 Å. The Ti(5)-O(11) bond length is 1.94 Å. The Ti(5)-O(13) bond length is 1.75 Å. The Ti(5)-O(25) bond length is 2.07 Å. Both Ti(5)-O(19) bond lengths are 1.98 Å. In the sixth Ti site, Ti(6) is bonded in a 6-coordinate geometry to one O(12), one O(14), one O(2), one O(26), and two equivalent O(20) atoms. The Ti(6)-O(12) bond length is 1.95 Å. The Ti(6)-O(14) bond length is 1.76 Å. The Ti(6)-O(2) bond length is 2.31 Å. The Ti(6)-O(26) bond length is 2.08 Å. Both Ti(6)-O(20) bond lengths are 1.96 Å. In the seventh Ti site, Ti(7) is bonded in a 6-coordinate geometry to one O(27), one O(3), one O(7), one O(9), and two equivalent O(15) atoms. The Ti(7)-O(27) bond length is 2.06 Å. The Ti(7)-O(3) bond length is 1.97 Å. The Ti(7)-O(7) bond length is 1.75 Å. The Ti(7)-O(9) bond length is 2.33 Å. Both Ti(7)-O(15) bond lengths are 1.96 Å. In the eighth Ti site, Ti(8) is bonded to one O(10), one O(28), one O(4), one O(8), and two equivalent O(16) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 8-31°. The Ti(8)-O(10) bond length is 2.25 Å. The Ti(8)-O(28) bond length is 2.12 Å. The Ti(8)-O(4) bond length is 1.90 Å. The Ti(8)-O(8) bond length is 1.80 Å. Both Ti(8)-O(16) bond lengths are 1.96 Å. In the ninth Ti site, Ti(9) is bonded to one O(1), one O(11), one O(22), one O(30), and two equivalent O(21) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 32°. The Ti(9)-O(1) bond length is 2.11 Å. The Ti(9)-O(11) bond length is 1.78 Å. The Ti(9)-O(22) bond length is 2.27 Å. The Ti(9)-O(30) bond length is 1.93 Å. Both Ti(9)-O(21) bond lengths are 1.96 Å. In the tenth Ti site, Ti(10) is bonded to one O(12), one O(2), one O(21), one O(29), and two equivalent O(22) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 30°. The Ti(10)-O(12) bond length is 1.84 Å. The Ti(10)-O(2) bond length is 2.17 Å. The Ti(10)-O(21) bond length is 2.19 Å. The Ti(10)-O(29) bond length is 1.88 Å. Both Ti(10)-O(22) bond lengths are 1.95 Å. In the eleventh Ti site, Ti(11) is bonded to one O(10), one O(15), one O(4), one O(5), and two equivalent O(9) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 34°. The Ti(11)-O(10) bond length is 2.26 Å. The Ti(11)-O(15) bond length is 2.19 Å. The Ti(11)-O(4) bond length is 1.89 Å. The Ti(11)-O(5) bond length is 1.79 Å. Both Ti(11)-O(9) bond lengths are 1.97 Å. In the twelfth Ti site, Ti(12) is bonded to one O(16), one O(3), one O(6), one O(9), and two equivalent O(10) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 33°. The Ti(12)-O(16) bond length is 2.28 Å. The Ti(12)-O(3) bond length is 1.83 Å. The Ti(12)-O(6) bond length is 1.86 Å. The Ti(12)-O(9) bond length is 2.17 Å. Both Ti(12)-O(10) bond lengths are 1.97 Å. In the thirteenth Ti site, Ti(13) is bonded to one O(17), one O(19), one O(23), one O(7), and two equivalent O(25) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 7-31°. The Ti(13)-O(17) bond length is 1.98 Å. The Ti(13)-O(19) bond length is 2.24 Å. The Ti(13)-O(23) bond length is 1.83 Å. The Ti(13)-O(7) bond length is 2.01 Å. Both Ti(13)-O(25) bond lengths are 1.95 Å. In the fourteenth Ti site, Ti(14) is bonded to one O(18), one O(20), one O(24), one O(8), and two equivalent O(26) atoms to form a mixture of distorted corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 5-27°. The Ti(14)-O(18) bond length is 2.11 Å. The Ti(14)-O(20) bond length is 2.19 Å. The Ti(14)-O(24) bond length is 1.84 Å. The Ti(14)-O(8) bond length is 1.91 Å. Both Ti(14)-O(26) bond lengths are 1.94 Å. There are thirty inequivalent O sites. In the first O site, O(1) is bonded to one Ti(5), one Ti(9), and two equivalent Ti(1) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(30)Na2Ti2 tetrahedra, corners with two equivalent O(29)Na2Ti2 tetrahedra,  a cornercorner with one O(22)Ti4 trigonal pyramid, corners with two equivalent O(1)Ti4 trigonal pyramids, edges with two equivalent O(19)Ti4 trigonal pyramids, and edges with two equivalent O(21)Ti4 trigonal pyramids. In the second O site, O(2) is bonded to one Ti(10), one Ti(6), and two equivalent Ti(2) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(29)Na2Ti2 tetrahedra, corners with two equivalent O(30)Na2Ti2 tetrahedra,  a cornercorner with one O(21)Ti4 trigonal pyramid, corners with two equivalent O(2)Ti4 trigonal pyramids, edges with two equivalent O(20)Ti4 trigonal pyramids, and edges with two equivalent O(22)Ti4 trigonal pyramids. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(3), one Ti(12), and one Ti(7) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(4), one Ti(11), and one Ti(8) atom. In the fifth O site, O(5) is bonded to two equivalent Na(3), one Ti(11), and one Ti(3) atom to form distorted ONa2Ti2 tetrahedra that share corners with two equivalent O(5)Na2Ti2 tetrahedra,  a cornercorner with one O(10)Ti4 trigonal pyramid, corners with two equivalent O(9)Ti4 trigonal pyramids, and  an edgeedge with one O(15)Ti4 trigonal pyramid. In the sixth O site, O(6) is bonded to two equivalent Na(4), one Ti(12), and one Ti(4) atom to form distorted ONa2Ti2 tetrahedra that share corners with two equivalent O(6)Na2Ti2 tetrahedra,  a cornercorner with one O(9)Ti4 trigonal pyramid, corners with two equivalent O(10)Ti4 trigonal pyramids, and  an edgeedge with one O(16)Ti4 trigonal pyramid. In the seventh O site, O(7) is bonded in a linear geometry to one Ti(13) and one Ti(7) atom. In the eighth O site, O(8) is bonded in a linear geometry to one Ti(14) and one Ti(8) atom. In the ninth O site, O(9) is bonded to one Ti(12), one Ti(7), and two equivalent Ti(11) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(6)Na2Ti2 tetrahedra, corners with two equivalent O(5)Na2Ti2 tetrahedra,  a cornercorner with one O(16)Ti4 trigonal pyramid, corners with two equivalent O(9)Ti4 trigonal pyramids, edges with two equivalent O(10)Ti4 trigonal pyramids, and edges with two equivalent O(15)Ti4 trigonal pyramids. In the tenth O site, O(10) is bonded to one Ti(11), one Ti(8), and two equivalent Ti(12) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(5)Na2Ti2 tetrahedra, corners with two equivalent O(6)Na2Ti2 tetrahedra,  a cornercorner with one O(15)Ti4 trigonal pyramid, corners with two equivalent O(10)Ti4 trigonal pyramids, edges with two equivalent O(16)Ti4 trigonal pyramids, and edges with two equivalent O(9)Ti4 trigonal pyramids. In the eleventh O site, O(11) is bonded in a water-like geometry to one Ti(5) and one Ti(9) atom. In the twelfth O site, O(12) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(2), one Ti(10), and one Ti(6) atom. In the thirteenth O site, O(13) is bonded in a linear geometry to one Ti(3) and one Ti(5) atom. In the fourteenth O site, O(14) is bonded in a distorted linear geometry to two equivalent Na(2), one Ti(4), and one Ti(6) atom. In the fifteenth O site, O(15) is bonded to one Ti(11), one Ti(3), and two equivalent Ti(7) atoms to form OTi4 trigonal pyramids that share  a cornercorner with one O(10)Ti4 trigonal pyramid, corners with two equivalent O(15)Ti4 trigonal pyramids,  an edgeedge with one O(5)Na2Ti2 tetrahedra, and edges with two equivalent O(9)Ti4 trigonal pyramids. In the sixteenth O site, O(16) is bonded to one Ti(12), one Ti(4), and two equivalent Ti(8) atoms to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(9)Ti4 trigonal pyramid, corners with two equivalent O(16)Ti4 trigonal pyramids,  an edgeedge with one O(6)Na2Ti2 tetrahedra, and edges with two equivalent O(10)Ti4 trigonal pyramids. In the seventeenth O site, O(17) is bonded in a water-like geometry to one Ti(1) and one Ti(13) atom. In the eighteenth O site, O(18) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(2), one Ti(14), and one Ti(2) atom. In the nineteenth O site, O(19) is bonded to one Ti(1), one Ti(13), and two equivalent Ti(5) atoms to form OTi4 trigonal pyramids that share  a cornercorner with one O(29)Na2Ti2 tetrahedra,  a cornercorner with one O(21)Ti4 trigonal pyramid, corners with two equivalent O(19)Ti4 trigonal pyramids, and edges with two equivalent O(1)Ti4 trigonal pyramids. In the twentieth O site, O(20) is bonded to one Ti(14), one Ti(2), and two equivalent Ti(6) atoms to form OTi4 trigonal pyramids that share  a cornercorner with one O(30)Na2Ti2 tetrahedra,  a cornercorner with one O(22)Ti4 trigonal pyramid, corners with two equivalent O(20)Ti4 trigonal pyramids, and edges with two equivalent O(2)Ti4 trigonal pyramids. In the twenty-first O site, O(21) is bonded to one Ti(1), one Ti(10), and two equivalent Ti(9) atoms to form distorted OTi4 trigonal pyramids that share corners with two equivalent O(30)Na2Ti2 tetrahedra,  a cornercorner with one O(19)Ti4 trigonal pyramid,  a cornercorner with one O(2)Ti4 trigonal pyramid, corners with two equivalent O(21)Ti4 trigonal pyramids,  an edgeedge with one O(29)Na2Ti2 tetrahedra, edges with two equivalent O(1)Ti4 trigonal pyramids, and edges with two equivalent O(22)Ti4 trigonal pyramids. In the twenty-second O site, O(22) is bonded to one Ti(2), one Ti(9), and two equivalent Ti(10) atoms to form distorted OTi4 trigonal pyramids that share corners with two equivalent O(29)Na2Ti2 tetrahedra,  a cornercorner with one O(1)Ti4 trigonal pyramid,  a cornercorner with one O(20)Ti4 trigonal pyramid, corners with two equivalent O(22)Ti4 trigonal pyramids,  an edgeedge with one O(30)Na2Ti2 tetrahedra, edges with two equivalent O(2)Ti4 trigonal pyramids, and edges with two equivalent O(21)Ti4 trigonal pyramids. In the twenty-third O site, O(23) is bonded in a linear geometry to one Ti(13) and one Ti(3) atom. In the twenty-fourth O site, O(24) is bonded in a linear geometry to one Ti(14) and one Ti(4) atom. In the twenty-fifth O site, O(25) is bonded in a distorted trigonal non-coplanar geometry to one Ti(5) and two equivalent Ti(13) atoms. In the twenty-sixth O site, O(26) is bonded in a distorted T-shaped geometry to one Ti(6) and two equivalent Ti(14) atoms. In the twenty-seventh O site, O(27) is bonded in a distorted T-shaped geometry to one Ti(7) and two equivalent Ti(3) atoms. In the twenty-eighth O site, O(28) is bonded in a distorted T-shaped geometry to one Ti(8) and two equivalent Ti(4) atoms. In the twenty-ninth O site, O(29) is bonded to two equivalent Na(1), one Ti(1), and one Ti(10) atom to form ONa2Ti2 tetrahedra that share corners with two equivalent O(29)Na2Ti2 tetrahedra, corners with two equivalent O(30)Na2Ti2 tetrahedra,  a cornercorner with one O(19)Ti4 trigonal pyramid,  a cornercorner with one O(2)Ti4 trigonal pyramid, corners with two equivalent O(1)Ti4 trigonal pyramids, corners with two equivalent O(22)Ti4 trigonal pyramids,  an edgeedge with one O(30)Na2Ti2 tetrahedra, and  an edgeedge with one O(21)Ti4 trigonal pyramid. In the thirtieth O site, O(30) is bonded to two equivalent Na(1), one Ti(2), and one Ti(9) atom to form ONa2Ti2 tetrahedra that share corners with two equivalent O(29)Na2Ti2 tetrahedra, corners with two equivalent O(30)Na2Ti2 tetrahedra,  a cornercorner with one O(1)Ti4 trigonal pyramid,  a cornercorner with one O(20)Ti4 trigonal pyramid, corners with two equivalent O(2)Ti4 trigonal pyramids, corners with two equivalent O(21)Ti4 trigonal pyramids,  an edgeedge with one O(29)Na2Ti2 tetrahedra, and  an edgeedge with one O(22)Ti4 trigonal pyramid.