Na4Mn2O5 crystallizes in the orthorhombic Fddd space group. Na(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NaO5 trigonal bipyramids that share corners with four equivalent Mn(1)O5 square pyramids, corners with five equivalent Na(1)O5 trigonal bipyramids, edges with three equivalent Mn(1)O5 square pyramids, and edges with five equivalent Na(1)O5 trigonal bipyramids. Mn(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form MnO5 square pyramids that share  a cornercorner with one Mn(1)O5 square pyramid, corners with eight equivalent Na(1)O5 trigonal bipyramids, edges with two equivalent Mn(1)O5 square pyramids, and edges with six equivalent Na(1)O5 trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Na(1) and two equivalent Mn(1) atoms to form a mixture of corner and edge-sharing ONa4Mn2 octahedra. The corner-sharing octahedral tilt angles are 1°. In the second O site, O(2) is bonded to four equivalent Na(1) and two equivalent Mn(1) atoms to form a mixture of distorted corner and edge-sharing ONa4Mn2 octahedra. The corner-sharing octahedral tilt angles range from 16-23°. In the third O site, O(3) is bonded to four equivalent Na(1) and two equivalent Mn(1) atoms to form a mixture of distorted corner and edge-sharing ONa4Mn2 octahedra. The corner-sharing octahedral tilt angles range from 1-23°.
Na4Mn2O5 crystallizes in the orthorhombic Fddd space group. Na(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NaO5 trigonal bipyramids that share corners with four equivalent Mn(1)O5 square pyramids, corners with five equivalent Na(1)O5 trigonal bipyramids, edges with three equivalent Mn(1)O5 square pyramids, and edges with five equivalent Na(1)O5 trigonal bipyramids. The Na(1)-O(1) bond length is 2.26 Å. There is one shorter (2.32 Å) and one longer (2.37 Å) Na(1)-O(2) bond length. There is one shorter (2.33 Å) and one longer (2.36 Å) Na(1)-O(3) bond length. Mn(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form MnO5 square pyramids that share  a cornercorner with one Mn(1)O5 square pyramid, corners with eight equivalent Na(1)O5 trigonal bipyramids, edges with two equivalent Mn(1)O5 square pyramids, and edges with six equivalent Na(1)O5 trigonal bipyramids. The Mn(1)-O(1) bond length is 2.05 Å. Both Mn(1)-O(2) bond lengths are 1.94 Å. Both Mn(1)-O(3) bond lengths are 1.95 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Na(1) and two equivalent Mn(1) atoms to form a mixture of corner and edge-sharing ONa4Mn2 octahedra. The corner-sharing octahedral tilt angles are 1°. In the second O site, O(2) is bonded to four equivalent Na(1) and two equivalent Mn(1) atoms to form a mixture of distorted corner and edge-sharing ONa4Mn2 octahedra. The corner-sharing octahedral tilt angles range from 16-23°. In the third O site, O(3) is bonded to four equivalent Na(1) and two equivalent Mn(1) atoms to form a mixture of distorted corner and edge-sharing ONa4Mn2 octahedra. The corner-sharing octahedral tilt angles range from 1-23°.