Na2Ti2O5 is Chalcostibite-like structured and crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(3), one O(5), and two equivalent O(2) atoms to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Ti(2)O4 tetrahedra, corners with two equivalent Ti(1)O4 tetrahedra, corners with two equivalent Na(2)O4 trigonal pyramids,  an edgeedge with one Ti(1)O4 tetrahedra,  an edgeedge with one Ti(2)O4 tetrahedra,  an edgeedge with one Na(1)O5 trigonal bipyramid, and  an edgeedge with one Na(2)O4 trigonal pyramid. In the second Na site, Na(2) is bonded to one O(2), one O(4), and two equivalent O(3) atoms to form NaO4 trigonal pyramids that share corners with two equivalent Ti(1)O4 tetrahedra, corners with three equivalent Ti(2)O4 tetrahedra, corners with two equivalent Na(1)O5 trigonal bipyramids,  an edgeedge with one Na(1)O5 trigonal bipyramid, and  an edgeedge with one Na(2)O4 trigonal pyramid. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(4), and one O(5) atom to form TiO4 tetrahedra that share corners with three equivalent Ti(2)O4 tetrahedra, corners with two equivalent Na(1)O5 trigonal bipyramids, corners with two equivalent Na(2)O4 trigonal pyramids, and  an edgeedge with one Na(1)O5 trigonal bipyramid. In the second Ti site, Ti(2) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form TiO4 tetrahedra that share corners with three equivalent Ti(1)O4 tetrahedra,  a cornercorner with one Na(1)O5 trigonal bipyramid, corners with three equivalent Na(2)O4 trigonal pyramids, and  an edgeedge with one Na(1)O5 trigonal bipyramid. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Na(1), one Ti(1), and one Ti(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(2), two equivalent Na(1), and one Ti(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), and one Ti(2) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Na(2), one Ti(1), and one Ti(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Na(1), one Ti(1), and one Ti(2) atom.
Na2Ti2O5 is Chalcostibite-like structured and crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(3), one O(5), and two equivalent O(2) atoms to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Ti(2)O4 tetrahedra, corners with two equivalent Ti(1)O4 tetrahedra, corners with two equivalent Na(2)O4 trigonal pyramids,  an edgeedge with one Ti(1)O4 tetrahedra,  an edgeedge with one Ti(2)O4 tetrahedra,  an edgeedge with one Na(1)O5 trigonal bipyramid, and  an edgeedge with one Na(2)O4 trigonal pyramid. The Na(1)-O(1) bond length is 2.40 Å. The Na(1)-O(3) bond length is 2.58 Å. The Na(1)-O(5) bond length is 2.57 Å. There is one shorter (2.41 Å) and one longer (2.60 Å) Na(1)-O(2) bond length. In the second Na site, Na(2) is bonded to one O(2), one O(4), and two equivalent O(3) atoms to form NaO4 trigonal pyramids that share corners with two equivalent Ti(1)O4 tetrahedra, corners with three equivalent Ti(2)O4 tetrahedra, corners with two equivalent Na(1)O5 trigonal bipyramids,  an edgeedge with one Na(1)O5 trigonal bipyramid, and  an edgeedge with one Na(2)O4 trigonal pyramid. The Na(2)-O(2) bond length is 2.39 Å. The Na(2)-O(4) bond length is 2.40 Å. There is one shorter (2.39 Å) and one longer (2.44 Å) Na(2)-O(3) bond length. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(4), and one O(5) atom to form TiO4 tetrahedra that share corners with three equivalent Ti(2)O4 tetrahedra, corners with two equivalent Na(1)O5 trigonal bipyramids, corners with two equivalent Na(2)O4 trigonal pyramids, and  an edgeedge with one Na(1)O5 trigonal bipyramid. The Ti(1)-O(1) bond length is 1.87 Å. The Ti(1)-O(2) bond length is 1.75 Å. The Ti(1)-O(4) bond length is 1.86 Å. The Ti(1)-O(5) bond length is 1.84 Å. In the second Ti site, Ti(2) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form TiO4 tetrahedra that share corners with three equivalent Ti(1)O4 tetrahedra,  a cornercorner with one Na(1)O5 trigonal bipyramid, corners with three equivalent Na(2)O4 trigonal pyramids, and  an edgeedge with one Na(1)O5 trigonal bipyramid. The Ti(2)-O(1) bond length is 1.87 Å. The Ti(2)-O(3) bond length is 1.75 Å. The Ti(2)-O(4) bond length is 1.87 Å. The Ti(2)-O(5) bond length is 1.84 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Na(1), one Ti(1), and one Ti(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(2), two equivalent Na(1), and one Ti(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), and one Ti(2) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Na(2), one Ti(1), and one Ti(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Na(1), one Ti(1), and one Ti(2) atom.