Na4Ti3O8 crystallizes in the monoclinic C2/m space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. In the second Na site, Na(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NaO6 octahedra that share corners with six equivalent Ti(1)O6 octahedra, edges with two equivalent Na(2)O6 octahedra, edges with two equivalent Na(3)O6 octahedra, edges with two equivalent Ti(1)O6 octahedra, and edges with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-15°. In the third Na site, Na(3) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form NaO6 octahedra that share edges with two equivalent Ti(2)O6 octahedra, edges with four equivalent Na(2)O6 octahedra, and edges with four equivalent Ti(1)O6 octahedra. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form TiO6 octahedra that share corners with six equivalent Na(2)O6 octahedra, edges with two equivalent Na(2)O6 octahedra, edges with two equivalent Na(3)O6 octahedra, edges with two equivalent Ti(1)O6 octahedra, and edges with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-15°. In the second Ti site, Ti(2) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form TiO6 octahedra that share edges with two equivalent Na(3)O6 octahedra, edges with four equivalent Na(2)O6 octahedra, and edges with four equivalent Ti(1)O6 octahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(2), one Ti(2), and two equivalent Ti(1) atoms to form ONa2Ti3 square pyramids that share corners with four equivalent O(3)Na3Ti2 square pyramids, corners with five equivalent O(1)Na2Ti3 square pyramids, edges with four equivalent O(2)Na4Ti2 octahedra, and edges with four equivalent O(3)Na3Ti2 square pyramids. In the second O site, O(2) is bonded to one Na(1), one Na(3), two equivalent Na(2), and two equivalent Ti(1) atoms to form distorted ONa4Ti2 octahedra that share corners with six equivalent O(2)Na4Ti2 octahedra, edges with four equivalent O(1)Na2Ti3 square pyramids, and edges with eight equivalent O(3)Na3Ti2 square pyramids. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to one Na(1), one Na(2), one Na(3), one Ti(1), and one Ti(2) atom to form distorted ONa3Ti2 square pyramids that share corners with two equivalent O(1)Na2Ti3 square pyramids, corners with seven equivalent O(3)Na3Ti2 square pyramids, edges with four equivalent O(2)Na4Ti2 octahedra, edges with two equivalent O(1)Na2Ti3 square pyramids, and edges with two equivalent O(3)Na3Ti2 square pyramids.
Na4Ti3O8 crystallizes in the monoclinic C2/m space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. Both Na(1)-O(2) bond lengths are 2.29 Å. All Na(1)-O(3) bond lengths are 2.34 Å. In the second Na site, Na(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NaO6 octahedra that share corners with six equivalent Ti(1)O6 octahedra, edges with two equivalent Na(2)O6 octahedra, edges with two equivalent Na(3)O6 octahedra, edges with two equivalent Ti(1)O6 octahedra, and edges with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-15°. Both Na(2)-O(1) bond lengths are 2.42 Å. Both Na(2)-O(2) bond lengths are 2.52 Å. Both Na(2)-O(3) bond lengths are 2.50 Å. In the third Na site, Na(3) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form NaO6 octahedra that share edges with two equivalent Ti(2)O6 octahedra, edges with four equivalent Na(2)O6 octahedra, and edges with four equivalent Ti(1)O6 octahedra. Both Na(3)-O(2) bond lengths are 2.20 Å. All Na(3)-O(3) bond lengths are 2.22 Å. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form TiO6 octahedra that share corners with six equivalent Na(2)O6 octahedra, edges with two equivalent Na(2)O6 octahedra, edges with two equivalent Na(3)O6 octahedra, edges with two equivalent Ti(1)O6 octahedra, and edges with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-15°. Both Ti(1)-O(1) bond lengths are 2.09 Å. Both Ti(1)-O(2) bond lengths are 2.00 Å. Both Ti(1)-O(3) bond lengths are 1.97 Å. In the second Ti site, Ti(2) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form TiO6 octahedra that share edges with two equivalent Na(3)O6 octahedra, edges with four equivalent Na(2)O6 octahedra, and edges with four equivalent Ti(1)O6 octahedra. Both Ti(2)-O(1) bond lengths are 2.06 Å. All Ti(2)-O(3) bond lengths are 1.96 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(2), one Ti(2), and two equivalent Ti(1) atoms to form ONa2Ti3 square pyramids that share corners with four equivalent O(3)Na3Ti2 square pyramids, corners with five equivalent O(1)Na2Ti3 square pyramids, edges with four equivalent O(2)Na4Ti2 octahedra, and edges with four equivalent O(3)Na3Ti2 square pyramids. In the second O site, O(2) is bonded to one Na(1), one Na(3), two equivalent Na(2), and two equivalent Ti(1) atoms to form distorted ONa4Ti2 octahedra that share corners with six equivalent O(2)Na4Ti2 octahedra, edges with four equivalent O(1)Na2Ti3 square pyramids, and edges with eight equivalent O(3)Na3Ti2 square pyramids. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to one Na(1), one Na(2), one Na(3), one Ti(1), and one Ti(2) atom to form distorted ONa3Ti2 square pyramids that share corners with two equivalent O(1)Na2Ti3 square pyramids, corners with seven equivalent O(3)Na3Ti2 square pyramids, edges with four equivalent O(2)Na4Ti2 octahedra, edges with two equivalent O(1)Na2Ti3 square pyramids, and edges with two equivalent O(3)Na3Ti2 square pyramids.