NaMn8O16 crystallizes in the orthorhombic Pmmn space group. Na(1) is bonded to two equivalent O(4) and two equivalent O(6) atoms to form NaO4 tetrahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent Mn(2)O6 octahedra, corners with four equivalent Mn(3)O6 octahedra, and corners with four equivalent Mn(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-62°. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MnO6 octahedra that share  a cornercorner with one Na(1)O4 tetrahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with two equivalent Mn(3)O6 octahedra. In the second Mn site, Mn(2) is bonded to one O(1), one O(6), two equivalent O(3), and two equivalent O(5) atoms to form MnO6 octahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  an edgeedge with one Mn(2)O6 octahedra,  an edgeedge with one Mn(3)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. In the third Mn site, Mn(3) is bonded to one O(2), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form MnO6 octahedra that share corners with two equivalent Na(1)O4 tetrahedra,  an edgeedge with one Mn(2)O6 octahedra,  an edgeedge with one Mn(3)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. In the fourth Mn site, Mn(4) is bonded to two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms to form MnO6 octahedra that share corners with two equivalent Na(1)O4 tetrahedra, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a distorted T-shaped geometry to one Mn(3) and two equivalent Mn(4) atoms. In the second O site, O(1) is bonded in a distorted T-shaped geometry to one Mn(2) and two equivalent Mn(1) atoms. In the third O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Mn(3) and two equivalent Mn(1) atoms. In the fourth O site, O(3) is bonded in a distorted T-shaped geometry to one Mn(1) and two equivalent Mn(2) atoms. In the fifth O site, O(4) is bonded to one Na(1), one Mn(1), and two equivalent Mn(3) atoms to form a mixture of corner and edge-sharing ONaMn3 tetrahedra. In the sixth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Mn(2), one Mn(3), and one Mn(4) atom. In the seventh O site, O(6) is bonded to one Na(1), one Mn(2), and two equivalent Mn(4) atoms to form corner-sharing ONaMn3 tetrahedra.
NaMn8O16 crystallizes in the orthorhombic Pmmn space group. Na(1) is bonded to two equivalent O(4) and two equivalent O(6) atoms to form NaO4 tetrahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent Mn(2)O6 octahedra, corners with four equivalent Mn(3)O6 octahedra, and corners with four equivalent Mn(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-62°. Both Na(1)-O(4) bond lengths are 2.11 Å. Both Na(1)-O(6) bond lengths are 2.11 Å. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MnO6 octahedra that share  a cornercorner with one Na(1)O4 tetrahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with two equivalent Mn(3)O6 octahedra. The Mn(1)-O(3) bond length is 1.94 Å. The Mn(1)-O(4) bond length is 1.95 Å. Both Mn(1)-O(1) bond lengths are 1.97 Å. Both Mn(1)-O(2) bond lengths are 1.96 Å. In the second Mn site, Mn(2) is bonded to one O(1), one O(6), two equivalent O(3), and two equivalent O(5) atoms to form MnO6 octahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  an edgeedge with one Mn(2)O6 octahedra,  an edgeedge with one Mn(3)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. The Mn(2)-O(1) bond length is 1.94 Å. The Mn(2)-O(6) bond length is 1.96 Å. Both Mn(2)-O(3) bond lengths are 1.97 Å. Both Mn(2)-O(5) bond lengths are 1.98 Å. In the third Mn site, Mn(3) is bonded to one O(2), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form MnO6 octahedra that share corners with two equivalent Na(1)O4 tetrahedra,  an edgeedge with one Mn(2)O6 octahedra,  an edgeedge with one Mn(3)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. The Mn(3)-O(2) bond length is 1.98 Å. The Mn(3)-O(7) bond length is 1.97 Å. Both Mn(3)-O(4) bond lengths are 1.97 Å. Both Mn(3)-O(5) bond lengths are 1.94 Å. In the fourth Mn site, Mn(4) is bonded to two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms to form MnO6 octahedra that share corners with two equivalent Na(1)O4 tetrahedra, edges with two equivalent Mn(2)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, and edges with two equivalent Mn(4)O6 octahedra. Both Mn(4)-O(5) bond lengths are 1.99 Å. Both Mn(4)-O(6) bond lengths are 1.95 Å. Both Mn(4)-O(7) bond lengths are 1.98 Å. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a distorted T-shaped geometry to one Mn(3) and two equivalent Mn(4) atoms. In the second O site, O(1) is bonded in a distorted T-shaped geometry to one Mn(2) and two equivalent Mn(1) atoms. In the third O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Mn(3) and two equivalent Mn(1) atoms. In the fourth O site, O(3) is bonded in a distorted T-shaped geometry to one Mn(1) and two equivalent Mn(2) atoms. In the fifth O site, O(4) is bonded to one Na(1), one Mn(1), and two equivalent Mn(3) atoms to form a mixture of corner and edge-sharing ONaMn3 tetrahedra. In the sixth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Mn(2), one Mn(3), and one Mn(4) atom. In the seventh O site, O(6) is bonded to one Na(1), one Mn(2), and two equivalent Mn(4) atoms to form corner-sharing ONaMn3 tetrahedra.