Na2Sb4O11 crystallizes in the trigonal R-3c space group. Na(1) is bonded in a 7-coordinate geometry to one O(3) and six equivalent O(1) atoms. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to two equivalent O(1), two equivalent O(3), and three equivalent O(2) atoms to form distorted SbO7 pentagonal bipyramids that share corners with two equivalent Sb(2)O6 octahedra, corners with two equivalent Sb(1)O7 pentagonal bipyramids, and edges with four equivalent Sb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 51°. In the second Sb site, Sb(2) is bonded to six equivalent O(1) atoms to form corner-sharing SbO6 octahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(1), one Sb(1), and one Sb(2) atom to form distorted ONa2Sb2 tetrahedra that share corners with two equivalent O(3)NaSb3 tetrahedra, corners with ten equivalent O(1)Na2Sb2 tetrahedra,  an edgeedge with one O(3)NaSb3 tetrahedra, and edges with three equivalent O(1)Na2Sb2 tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to three equivalent Sb(1) atoms. In the third O site, O(3) is bonded to one Na(1) and three equivalent Sb(1) atoms to form distorted ONaSb3 tetrahedra that share corners with three equivalent O(3)NaSb3 tetrahedra, corners with six equivalent O(1)Na2Sb2 tetrahedra, and edges with three equivalent O(1)Na2Sb2 tetrahedra.
Na2Sb4O11 crystallizes in the trigonal R-3c space group. Na(1) is bonded in a 7-coordinate geometry to one O(3) and six equivalent O(1) atoms. The Na(1)-O(3) bond length is 2.66 Å. There are three shorter (2.48 Å) and three longer (2.60 Å) Na(1)-O(1) bond lengths. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to two equivalent O(1), two equivalent O(3), and three equivalent O(2) atoms to form distorted SbO7 pentagonal bipyramids that share corners with two equivalent Sb(2)O6 octahedra, corners with two equivalent Sb(1)O7 pentagonal bipyramids, and edges with four equivalent Sb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 51°. Both Sb(1)-O(1) bond lengths are 1.97 Å. Both Sb(1)-O(3) bond lengths are 2.07 Å. There are two shorter (2.03 Å) and one longer (2.42 Å) Sb(1)-O(2) bond length. In the second Sb site, Sb(2) is bonded to six equivalent O(1) atoms to form corner-sharing SbO6 octahedra. All Sb(2)-O(1) bond lengths are 2.04 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(1), one Sb(1), and one Sb(2) atom to form distorted ONa2Sb2 tetrahedra that share corners with two equivalent O(3)NaSb3 tetrahedra, corners with ten equivalent O(1)Na2Sb2 tetrahedra,  an edgeedge with one O(3)NaSb3 tetrahedra, and edges with three equivalent O(1)Na2Sb2 tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to three equivalent Sb(1) atoms. In the third O site, O(3) is bonded to one Na(1) and three equivalent Sb(1) atoms to form distorted ONaSb3 tetrahedra that share corners with three equivalent O(3)NaSb3 tetrahedra, corners with six equivalent O(1)Na2Sb2 tetrahedra, and edges with three equivalent O(1)Na2Sb2 tetrahedra.