Na8NbO6 crystallizes in the hexagonal P6_3cm space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form distorted NaO4 tetrahedra that share corners with two equivalent Nb(1)O4 tetrahedra, corners with four equivalent Na(2)O4 tetrahedra, corners with six equivalent Na(1)O4 tetrahedra, edges with two equivalent Na(3)O4 tetrahedra, and edges with three equivalent Na(2)O4 tetrahedra. In the second Na site, Na(2) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form distorted NaO4 tetrahedra that share corners with four equivalent Na(1)O4 tetrahedra, corners with four equivalent Na(3)O4 tetrahedra, corners with six equivalent Na(2)O4 tetrahedra,  an edgeedge with one Nb(1)O4 tetrahedra, and edges with three equivalent Na(1)O4 tetrahedra. In the third Na site, Na(3) is bonded to one O(2) and three equivalent O(1) atoms to form NaO4 tetrahedra that share corners with three equivalent Na(3)O4 tetrahedra, corners with three equivalent Nb(1)O4 tetrahedra, corners with six equivalent Na(2)O4 tetrahedra, and edges with three equivalent Na(1)O4 tetrahedra. Nb(1) is bonded to one O(3) and three equivalent O(1) atoms to form NbO4 tetrahedra that share corners with six equivalent Na(1)O4 tetrahedra, corners with six equivalent Na(3)O4 tetrahedra, and edges with three equivalent Na(2)O4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), two equivalent Na(3), and one Nb(1) atom to form ONa4Nb trigonal bipyramids that share corners with two equivalent O(2)Na7 pentagonal bipyramids, corners with six equivalent O(1)Na4Nb trigonal bipyramids, and edges with two equivalent O(2)Na7 pentagonal bipyramids. In the second O site, O(2) is bonded to one Na(3), three equivalent Na(1), and three equivalent Na(2) atoms to form distorted ONa7 pentagonal bipyramids that share corners with three equivalent O(1)Na4Nb trigonal bipyramids, edges with three equivalent O(2)Na7 pentagonal bipyramids, and edges with three equivalent O(1)Na4Nb trigonal bipyramids. In the third O site, O(3) is bonded in a 7-coordinate geometry to three equivalent Na(1), three equivalent Na(2), and one Nb(1) atom.
Na8NbO6 crystallizes in the hexagonal P6_3cm space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form distorted NaO4 tetrahedra that share corners with two equivalent Nb(1)O4 tetrahedra, corners with four equivalent Na(2)O4 tetrahedra, corners with six equivalent Na(1)O4 tetrahedra, edges with two equivalent Na(3)O4 tetrahedra, and edges with three equivalent Na(2)O4 tetrahedra. The Na(1)-O(1) bond length is 2.44 Å. The Na(1)-O(3) bond length is 2.67 Å. Both Na(1)-O(2) bond lengths are 2.36 Å. In the second Na site, Na(2) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form distorted NaO4 tetrahedra that share corners with four equivalent Na(1)O4 tetrahedra, corners with four equivalent Na(3)O4 tetrahedra, corners with six equivalent Na(2)O4 tetrahedra,  an edgeedge with one Nb(1)O4 tetrahedra, and edges with three equivalent Na(1)O4 tetrahedra. The Na(2)-O(1) bond length is 2.45 Å. The Na(2)-O(3) bond length is 2.60 Å. Both Na(2)-O(2) bond lengths are 2.36 Å. In the third Na site, Na(3) is bonded to one O(2) and three equivalent O(1) atoms to form NaO4 tetrahedra that share corners with three equivalent Na(3)O4 tetrahedra, corners with three equivalent Nb(1)O4 tetrahedra, corners with six equivalent Na(2)O4 tetrahedra, and edges with three equivalent Na(1)O4 tetrahedra. The Na(3)-O(2) bond length is 2.47 Å. All Na(3)-O(1) bond lengths are 2.44 Å. Nb(1) is bonded to one O(3) and three equivalent O(1) atoms to form NbO4 tetrahedra that share corners with six equivalent Na(1)O4 tetrahedra, corners with six equivalent Na(3)O4 tetrahedra, and edges with three equivalent Na(2)O4 tetrahedra. The Nb(1)-O(3) bond length is 1.90 Å. All Nb(1)-O(1) bond lengths are 1.90 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), two equivalent Na(3), and one Nb(1) atom to form ONa4Nb trigonal bipyramids that share corners with two equivalent O(2)Na7 pentagonal bipyramids, corners with six equivalent O(1)Na4Nb trigonal bipyramids, and edges with two equivalent O(2)Na7 pentagonal bipyramids. In the second O site, O(2) is bonded to one Na(3), three equivalent Na(1), and three equivalent Na(2) atoms to form distorted ONa7 pentagonal bipyramids that share corners with three equivalent O(1)Na4Nb trigonal bipyramids, edges with three equivalent O(2)Na7 pentagonal bipyramids, and edges with three equivalent O(1)Na4Nb trigonal bipyramids. In the third O site, O(3) is bonded in a 7-coordinate geometry to three equivalent Na(1), three equivalent Na(2), and one Nb(1) atom.