Na2TiSiO5 crystallizes in the orthorhombic Pmc2_1 space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NaO6 octahedra that share corners with two equivalent Na(1)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra,  a cornercorner with one Ti(1)O5 trigonal bipyramid,  a cornercorner with one Ti(2)O5 trigonal bipyramid, edges with two equivalent Na(2)O6 octahedra,  an edgeedge with one Ti(1)O5 trigonal bipyramid, and  an edgeedge with one Ti(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 41°. In the second Na site, Na(2) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form distorted NaO6 octahedra that share corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, corners with two equivalent Ti(1)O5 trigonal bipyramids, edges with four equivalent Na(1)O6 octahedra, and edges with two equivalent Ti(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 38°. In the third Na site, Na(3) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(5) atoms to form distorted TiO5 trigonal bipyramids that share corners with two equivalent Na(1)O6 octahedra, corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, edges with two equivalent Na(1)O6 octahedra, and edges with two equivalent Na(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 69-71°. In the second Ti site, Ti(2) is bonded to one O(6), two equivalent O(2), and two equivalent O(3) atoms to form distorted TiO5 trigonal bipyramids that share corners with two equivalent Na(1)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles are 68°. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form SiO4 tetrahedra that share corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Na(1)O6 octahedra, corners with two equivalent Ti(1)O5 trigonal bipyramids, and corners with two equivalent Ti(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 62-73°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Ti(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(3), one Ti(2), and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(3), one Ti(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and one Ti(1) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Ti(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to two equivalent Na(1), two equivalent Na(3), and one Ti(2) atom.
Na2TiSiO5 crystallizes in the orthorhombic Pmc2_1 space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NaO6 octahedra that share corners with two equivalent Na(1)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra,  a cornercorner with one Ti(1)O5 trigonal bipyramid,  a cornercorner with one Ti(2)O5 trigonal bipyramid, edges with two equivalent Na(2)O6 octahedra,  an edgeedge with one Ti(1)O5 trigonal bipyramid, and  an edgeedge with one Ti(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 41°. The Na(1)-O(1) bond length is 2.31 Å. The Na(1)-O(2) bond length is 2.33 Å. The Na(1)-O(3) bond length is 2.40 Å. The Na(1)-O(4) bond length is 2.44 Å. The Na(1)-O(5) bond length is 2.32 Å. The Na(1)-O(6) bond length is 2.45 Å. In the second Na site, Na(2) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form distorted NaO6 octahedra that share corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, corners with two equivalent Ti(1)O5 trigonal bipyramids, edges with four equivalent Na(1)O6 octahedra, and edges with two equivalent Ti(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 38°. Both Na(2)-O(1) bond lengths are 2.43 Å. There is one shorter (2.55 Å) and one longer (2.62 Å) Na(2)-O(4) bond length. Both Na(2)-O(5) bond lengths are 2.41 Å. In the third Na site, Na(3) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms. Both Na(3)-O(2) bond lengths are 2.30 Å. Both Na(3)-O(3) bond lengths are 2.39 Å. There is one shorter (2.20 Å) and one longer (2.69 Å) Na(3)-O(6) bond length. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(5) atoms to form distorted TiO5 trigonal bipyramids that share corners with two equivalent Na(1)O6 octahedra, corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, edges with two equivalent Na(1)O6 octahedra, and edges with two equivalent Na(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 69-71°. The Ti(1)-O(4) bond length is 1.73 Å. Both Ti(1)-O(1) bond lengths are 1.96 Å. Both Ti(1)-O(5) bond lengths are 1.96 Å. In the second Ti site, Ti(2) is bonded to one O(6), two equivalent O(2), and two equivalent O(3) atoms to form distorted TiO5 trigonal bipyramids that share corners with two equivalent Na(1)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles are 68°. The Ti(2)-O(6) bond length is 1.72 Å. Both Ti(2)-O(2) bond lengths are 1.99 Å. Both Ti(2)-O(3) bond lengths are 1.96 Å. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form SiO4 tetrahedra that share corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Na(1)O6 octahedra, corners with two equivalent Ti(1)O5 trigonal bipyramids, and corners with two equivalent Ti(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 62-73°. The Si(1)-O(1) bond length is 1.62 Å. The Si(1)-O(2) bond length is 1.63 Å. The Si(1)-O(3) bond length is 1.63 Å. The Si(1)-O(5) bond length is 1.62 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Ti(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(3), one Ti(2), and one Si(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(3), one Ti(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and one Ti(1) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Ti(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to two equivalent Na(1), two equivalent Na(3), and one Ti(2) atom.