NaMn2O4 is Spinel-like structured and crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form NaO4 tetrahedra that share corners with six equivalent Mn(1)O6 octahedra and corners with six equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-67°. In the second Na site, Na(2) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form NaO4 tetrahedra that share corners with six equivalent Mn(1)O6 octahedra and corners with six equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-72°. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MnO6 octahedra that share corners with three equivalent Na(1)O4 tetrahedra, corners with three equivalent Na(2)O4 tetrahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. In the second Mn site, Mn(2) 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 corners with three equivalent Na(1)O4 tetrahedra, corners with three equivalent Na(2)O4 tetrahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with four equivalent Mn(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Mn(1), and two equivalent Mn(2) atoms to form a mixture of corner and edge-sharing ONaMn3 tetrahedra. In the second O site, O(2) is bonded to one Na(2), one Mn(1), and two equivalent Mn(2) atoms to form a mixture of distorted corner and edge-sharing ONaMn3 trigonal pyramids. In the third O site, O(3) is bonded to one Na(1), one Mn(2), and two equivalent Mn(1) atoms to form a mixture of distorted corner and edge-sharing ONaMn3 tetrahedra. In the fourth O site, O(4) is bonded to one Na(2), one Mn(2), and two equivalent Mn(1) atoms to form a mixture of corner and edge-sharing ONaMn3 tetrahedra.
NaMn2O4 is Spinel-like structured and crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form NaO4 tetrahedra that share corners with six equivalent Mn(1)O6 octahedra and corners with six equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-67°. Both Na(1)-O(1) bond lengths are 2.17 Å. Both Na(1)-O(3) bond lengths are 2.18 Å. In the second Na site, Na(2) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form NaO4 tetrahedra that share corners with six equivalent Mn(1)O6 octahedra and corners with six equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-72°. Both Na(2)-O(2) bond lengths are 2.18 Å. Both Na(2)-O(4) bond lengths are 2.22 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MnO6 octahedra that share corners with three equivalent Na(1)O4 tetrahedra, corners with three equivalent Na(2)O4 tetrahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The Mn(1)-O(1) bond length is 2.00 Å. The Mn(1)-O(2) bond length is 2.27 Å. There is one shorter (1.95 Å) and one longer (2.31 Å) Mn(1)-O(3) bond length. There is one shorter (2.01 Å) and one longer (2.03 Å) Mn(1)-O(4) bond length. In the second Mn site, Mn(2) 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 corners with three equivalent Na(1)O4 tetrahedra, corners with three equivalent Na(2)O4 tetrahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with four equivalent Mn(1)O6 octahedra. The Mn(2)-O(3) bond length is 1.95 Å. The Mn(2)-O(4) bond length is 1.99 Å. Both Mn(2)-O(1) bond lengths are 1.98 Å. There is one shorter (1.91 Å) and one longer (1.95 Å) Mn(2)-O(2) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Mn(1), and two equivalent Mn(2) atoms to form a mixture of corner and edge-sharing ONaMn3 tetrahedra. In the second O site, O(2) is bonded to one Na(2), one Mn(1), and two equivalent Mn(2) atoms to form a mixture of distorted corner and edge-sharing ONaMn3 trigonal pyramids. In the third O site, O(3) is bonded to one Na(1), one Mn(2), and two equivalent Mn(1) atoms to form a mixture of distorted corner and edge-sharing ONaMn3 tetrahedra. In the fourth O site, O(4) is bonded to one Na(2), one Mn(2), and two equivalent Mn(1) atoms to form a mixture of corner and edge-sharing ONaMn3 tetrahedra.