Na2Si3O7 crystallizes in the monoclinic C2/c space group. Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), and three equivalent O(4) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form corner-sharing SiO6 octahedra. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with three equivalent Si(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 21-57°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal pyramidal geometry to two equivalent Na(1) and two equivalent Si(2) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to three equivalent Na(1), one Si(1), and one Si(2) atom.
Na2Si3O7 crystallizes in the monoclinic C2/c space group. Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), and three equivalent O(4) atoms. The Na(1)-O(1) bond length is 2.42 Å. The Na(1)-O(2) bond length is 2.35 Å. The Na(1)-O(3) bond length is 2.66 Å. There are a spread of Na(1)-O(4) bond distances ranging from 2.51-2.77 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form corner-sharing SiO6 octahedra. Both Si(1)-O(2) bond lengths are 1.80 Å. Both Si(1)-O(3) bond lengths are 1.78 Å. Both Si(1)-O(4) bond lengths are 1.85 Å. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with three equivalent Si(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 21-57°. The Si(2)-O(1) bond length is 1.68 Å. The Si(2)-O(2) bond length is 1.64 Å. The Si(2)-O(3) bond length is 1.60 Å. The Si(2)-O(4) bond length is 1.65 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal pyramidal geometry to two equivalent Na(1) and two equivalent Si(2) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to three equivalent Na(1), one Si(1), and one Si(2) atom.