Na10Fe4O9 crystallizes in the monoclinic Cm space group. There are twelve inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(1), one O(10), one O(12), and one O(3) atom. In the second Na site, Na(2) is bonded to one O(1), one O(11), one O(12), and one O(4) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra,  a cornercorner with one Fe(4)O4 tetrahedra,  a cornercorner with one Fe(5)O4 tetrahedra,  a cornercorner with one Na(5)O5 trigonal bipyramid, and  an edgeedge with one Na(12)O5 trigonal bipyramid. In the third Na site, Na(3) is bonded in a 6-coordinate geometry to one O(1), one O(3), one O(4), one O(6), one O(8), and one O(9) atom. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), one O(4), and one O(6) atom. In the fifth Na site, Na(5) is bonded to one O(5), one O(7), one O(8), and two equivalent O(4) atoms to form distorted NaO5 trigonal bipyramids that share corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra, edges with two equivalent Na(8)O4 tetrahedra, and edges with two equivalent Fe(3)O4 tetrahedra. In the sixth Na site, Na(6) is bonded in a distorted trigonal non-coplanar geometry to one O(3), one O(4), and one O(8) atom. In the seventh Na site, Na(7) is bonded in a 3-coordinate geometry to one O(6), two equivalent O(10), and two equivalent O(3) atoms. In the eighth Na site, Na(8) is bonded to one O(10), one O(12), one O(5), and one O(7) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Fe(4)O4 tetrahedra,  a cornercorner with one Fe(5)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra,  an edgeedge with one Na(8)O4 tetrahedra,  an edgeedge with one Na(12)O5 trigonal bipyramid, and  an edgeedge with one Na(5)O5 trigonal bipyramid. In the ninth Na site, Na(9) is bonded in a 4-coordinate geometry to one O(1), one O(10), one O(5), and one O(9) atom. In the tenth Na site, Na(10) is bonded to one O(5), one O(8), and two equivalent O(9) atoms to form NaO4 tetrahedra that share corners with two equivalent Na(8)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Na(12)O5 trigonal bipyramids, and  an edgeedge with one Na(5)O5 trigonal bipyramid. In the eleventh Na site, Na(11) is bonded in a 4-coordinate geometry to one O(11), one O(7), and two equivalent O(12) atoms. In the twelfth Na site, Na(12) is bonded to one O(1), one O(10), one O(12), one O(2), and one O(9) atom to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra,  a cornercorner with one Na(12)O5 trigonal bipyramid,  an edgeedge with one Na(2)O4 tetrahedra,  an edgeedge with one Na(8)O4 tetrahedra,  an edgeedge with one Fe(4)O4 tetrahedra, and  an edgeedge with one Fe(5)O4 tetrahedra. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a trigonal planar geometry to one O(8) and two equivalent O(12) atoms. In the second Fe site, Fe(2) is bonded to one O(11), one O(2), and two equivalent O(3) atoms to form distorted FeO4 tetrahedra that share corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Na(12)O5 trigonal bipyramids, and  an edgeedge with one Fe(5)O4 tetrahedra. In the third Fe site, Fe(3) is bonded to one O(3), one O(4), one O(7), and one O(9) atom to form distorted FeO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra, corners with two equivalent Na(8)O4 tetrahedra,  a cornercorner with one Na(12)O5 trigonal bipyramid,  an edgeedge with one Fe(4)O4 tetrahedra, and  an edgeedge with one Na(5)O5 trigonal bipyramid. In the fourth Fe site, Fe(4) is bonded to one O(10), one O(4), one O(6), and one O(9) atom to form distorted FeO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Fe(4)O4 tetrahedra,  a cornercorner with one Fe(5)O4 tetrahedra,  a cornercorner with one Na(5)O5 trigonal bipyramid,  an edgeedge with one Fe(3)O4 tetrahedra, and  an edgeedge with one Na(12)O5 trigonal bipyramid. In the fifth Fe site, Fe(5) is bonded to one O(11), one O(2), and two equivalent O(10) atoms to form distorted FeO4 tetrahedra that share corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Na(8)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra,  an edgeedge with one Fe(2)O4 tetrahedra, and edges with two equivalent Na(12)O5 trigonal bipyramids. In the sixth Fe site, Fe(6) is bonded in a trigonal planar geometry to one O(5) and two equivalent O(1) atoms. There are twelve inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(12), one Na(2), one Na(3), one Na(4), one Na(9), and one Fe(6) atom to form distorted ONa6Fe pentagonal bipyramids that share  a cornercorner with one O(1)Na6Fe pentagonal bipyramid,  a cornercorner with one O(8)Na6Fe pentagonal bipyramid, and  a cornercorner with one O(11)Na3Fe2 trigonal bipyramid. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Na(12), two equivalent Na(4), one Fe(2), and one Fe(5) atom. In the third O site, O(3) is bonded in a 7-coordinate geometry to one Na(1), one Na(3), one Na(4), one Na(6), one Na(7), one Fe(2), and one Fe(3) atom. In the fourth O site, O(4) is bonded in a 7-coordinate geometry to one Na(2), one Na(3), one Na(4), one Na(5), one Na(6), one Fe(3), and one Fe(4) atom. In the fifth O site, O(5) is bonded in a 7-coordinate geometry to one Na(10), one Na(5), two equivalent Na(8), two equivalent Na(9), and one Fe(6) atom. In the sixth O site, O(6) is bonded in a 7-coordinate geometry to one Na(7), two equivalent Na(3), two equivalent Na(4), and two equivalent Fe(4) atoms. In the seventh O site, O(7) is bonded in a 6-coordinate geometry to one Na(11), one Na(5), two equivalent Na(8), and two equivalent Fe(3) atoms. In the eighth O site, O(8) is bonded to one Na(10), one Na(5), two equivalent Na(3), two equivalent Na(6), and one Fe(1) atom to form distorted corner-sharing ONa6Fe pentagonal bipyramids. In the ninth O site, O(9) is bonded in a 5-coordinate geometry to one Na(10), one Na(12), one Na(3), one Na(9), one Fe(3), and one Fe(4) atom. In the tenth O site, O(10) is bonded in a 7-coordinate geometry to one Na(1), one Na(12), one Na(7), one Na(8), one Na(9), one Fe(4), and one Fe(5) atom. In the eleventh O site, O(11) is bonded to one Na(11), two equivalent Na(2), one Fe(2), and one Fe(5) atom to form corner-sharing ONa3Fe2 trigonal bipyramids. In the twelfth O site, O(12) is bonded in a 6-coordinate geometry to one Na(1), one Na(11), one Na(12), one Na(2), one Na(8), and one Fe(1) atom.
Na10Fe4O9 crystallizes in the monoclinic Cm space group. There are twelve inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(1), one O(10), one O(12), and one O(3) atom. The Na(1)-O(1) bond length is 2.42 Å. The Na(1)-O(10) bond length is 2.65 Å. The Na(1)-O(12) bond length is 2.34 Å. The Na(1)-O(3) bond length is 2.51 Å. In the second Na site, Na(2) is bonded to one O(1), one O(11), one O(12), and one O(4) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra,  a cornercorner with one Fe(4)O4 tetrahedra,  a cornercorner with one Fe(5)O4 tetrahedra,  a cornercorner with one Na(5)O5 trigonal bipyramid, and  an edgeedge with one Na(12)O5 trigonal bipyramid. The Na(2)-O(1) bond length is 2.40 Å. The Na(2)-O(11) bond length is 2.32 Å. The Na(2)-O(12) bond length is 2.37 Å. The Na(2)-O(4) bond length is 2.35 Å. In the third Na site, Na(3) is bonded in a 6-coordinate geometry to one O(1), one O(3), one O(4), one O(6), one O(8), and one O(9) atom. The Na(3)-O(1) bond length is 2.35 Å. The Na(3)-O(3) bond length is 2.78 Å. The Na(3)-O(4) bond length is 2.79 Å. The Na(3)-O(6) bond length is 2.63 Å. The Na(3)-O(8) bond length is 2.41 Å. The Na(3)-O(9) bond length is 2.83 Å. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), one O(4), and one O(6) atom. The Na(4)-O(1) bond length is 2.57 Å. The Na(4)-O(2) bond length is 2.41 Å. The Na(4)-O(3) bond length is 2.76 Å. The Na(4)-O(4) bond length is 2.60 Å. The Na(4)-O(6) bond length is 2.39 Å. In the fifth Na site, Na(5) is bonded to one O(5), one O(7), one O(8), and two equivalent O(4) atoms to form distorted NaO5 trigonal bipyramids that share corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra, edges with two equivalent Na(8)O4 tetrahedra, and edges with two equivalent Fe(3)O4 tetrahedra. The Na(5)-O(5) bond length is 2.64 Å. The Na(5)-O(7) bond length is 2.53 Å. The Na(5)-O(8) bond length is 2.64 Å. Both Na(5)-O(4) bond lengths are 2.43 Å. In the sixth Na site, Na(6) is bonded in a distorted trigonal non-coplanar geometry to one O(3), one O(4), and one O(8) atom. The Na(6)-O(3) bond length is 2.24 Å. The Na(6)-O(4) bond length is 2.30 Å. The Na(6)-O(8) bond length is 2.35 Å. In the seventh Na site, Na(7) is bonded in a 3-coordinate geometry to one O(6), two equivalent O(10), and two equivalent O(3) atoms. The Na(7)-O(6) bond length is 2.54 Å. Both Na(7)-O(10) bond lengths are 2.94 Å. Both Na(7)-O(3) bond lengths are 2.65 Å. In the eighth Na site, Na(8) is bonded to one O(10), one O(12), one O(5), and one O(7) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Fe(4)O4 tetrahedra,  a cornercorner with one Fe(5)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra,  an edgeedge with one Na(8)O4 tetrahedra,  an edgeedge with one Na(12)O5 trigonal bipyramid, and  an edgeedge with one Na(5)O5 trigonal bipyramid. The Na(8)-O(10) bond length is 2.49 Å. The Na(8)-O(12) bond length is 2.33 Å. The Na(8)-O(5) bond length is 2.35 Å. The Na(8)-O(7) bond length is 2.52 Å. In the ninth Na site, Na(9) is bonded in a 4-coordinate geometry to one O(1), one O(10), one O(5), and one O(9) atom. The Na(9)-O(1) bond length is 2.38 Å. The Na(9)-O(10) bond length is 2.26 Å. The Na(9)-O(5) bond length is 2.74 Å. The Na(9)-O(9) bond length is 2.28 Å. In the tenth Na site, Na(10) is bonded to one O(5), one O(8), and two equivalent O(9) atoms to form NaO4 tetrahedra that share corners with two equivalent Na(8)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Na(12)O5 trigonal bipyramids, and  an edgeedge with one Na(5)O5 trigonal bipyramid. The Na(10)-O(5) bond length is 2.33 Å. The Na(10)-O(8) bond length is 2.40 Å. Both Na(10)-O(9) bond lengths are 2.30 Å. In the eleventh Na site, Na(11) is bonded in a 4-coordinate geometry to one O(11), one O(7), and two equivalent O(12) atoms. The Na(11)-O(11) bond length is 2.30 Å. The Na(11)-O(7) bond length is 2.31 Å. Both Na(11)-O(12) bond lengths are 2.51 Å. In the twelfth Na site, Na(12) is bonded to one O(1), one O(10), one O(12), one O(2), and one O(9) atom to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra,  a cornercorner with one Na(12)O5 trigonal bipyramid,  an edgeedge with one Na(2)O4 tetrahedra,  an edgeedge with one Na(8)O4 tetrahedra,  an edgeedge with one Fe(4)O4 tetrahedra, and  an edgeedge with one Fe(5)O4 tetrahedra. The Na(12)-O(1) bond length is 2.54 Å. The Na(12)-O(10) bond length is 2.75 Å. The Na(12)-O(12) bond length is 2.48 Å. The Na(12)-O(2) bond length is 2.39 Å. The Na(12)-O(9) bond length is 2.40 Å. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a trigonal planar geometry to one O(8) and two equivalent O(12) atoms. The Fe(1)-O(8) bond length is 1.94 Å. Both Fe(1)-O(12) bond lengths are 1.95 Å. In the second Fe site, Fe(2) is bonded to one O(11), one O(2), and two equivalent O(3) atoms to form distorted FeO4 tetrahedra that share corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Na(12)O5 trigonal bipyramids, and  an edgeedge with one Fe(5)O4 tetrahedra. The Fe(2)-O(11) bond length is 2.07 Å. The Fe(2)-O(2) bond length is 2.10 Å. Both Fe(2)-O(3) bond lengths are 2.00 Å. In the third Fe site, Fe(3) is bonded to one O(3), one O(4), one O(7), and one O(9) atom to form distorted FeO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Fe(2)O4 tetrahedra,  a cornercorner with one Fe(3)O4 tetrahedra, corners with two equivalent Na(8)O4 tetrahedra,  a cornercorner with one Na(12)O5 trigonal bipyramid,  an edgeedge with one Fe(4)O4 tetrahedra, and  an edgeedge with one Na(5)O5 trigonal bipyramid. The Fe(3)-O(3) bond length is 2.02 Å. The Fe(3)-O(4) bond length is 2.12 Å. The Fe(3)-O(7) bond length is 2.01 Å. The Fe(3)-O(9) bond length is 2.08 Å. In the fourth Fe site, Fe(4) is bonded to one O(10), one O(4), one O(6), and one O(9) atom to form distorted FeO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Fe(4)O4 tetrahedra,  a cornercorner with one Fe(5)O4 tetrahedra,  a cornercorner with one Na(5)O5 trigonal bipyramid,  an edgeedge with one Fe(3)O4 tetrahedra, and  an edgeedge with one Na(12)O5 trigonal bipyramid. The Fe(4)-O(10) bond length is 2.00 Å. The Fe(4)-O(4) bond length is 2.10 Å. The Fe(4)-O(6) bond length is 2.03 Å. The Fe(4)-O(9) bond length is 2.10 Å. In the fifth Fe site, Fe(5) is bonded to one O(11), one O(2), and two equivalent O(10) atoms to form distorted FeO4 tetrahedra that share corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Na(8)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra,  an edgeedge with one Fe(2)O4 tetrahedra, and edges with two equivalent Na(12)O5 trigonal bipyramids. The Fe(5)-O(11) bond length is 2.08 Å. The Fe(5)-O(2) bond length is 2.12 Å. Both Fe(5)-O(10) bond lengths are 2.01 Å. In the sixth Fe site, Fe(6) is bonded in a trigonal planar geometry to one O(5) and two equivalent O(1) atoms. The Fe(6)-O(5) bond length is 1.96 Å. Both Fe(6)-O(1) bond lengths are 1.94 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(12), one Na(2), one Na(3), one Na(4), one Na(9), and one Fe(6) atom to form distorted ONa6Fe pentagonal bipyramids that share  a cornercorner with one O(1)Na6Fe pentagonal bipyramid,  a cornercorner with one O(8)Na6Fe pentagonal bipyramid, and  a cornercorner with one O(11)Na3Fe2 trigonal bipyramid. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Na(12), two equivalent Na(4), one Fe(2), and one Fe(5) atom. In the third O site, O(3) is bonded in a 7-coordinate geometry to one Na(1), one Na(3), one Na(4), one Na(6), one Na(7), one Fe(2), and one Fe(3) atom. In the fourth O site, O(4) is bonded in a 7-coordinate geometry to one Na(2), one Na(3), one Na(4), one Na(5), one Na(6), one Fe(3), and one Fe(4) atom. In the fifth O site, O(5) is bonded in a 7-coordinate geometry to one Na(10), one Na(5), two equivalent Na(8), two equivalent Na(9), and one Fe(6) atom. In the sixth O site, O(6) is bonded in a 7-coordinate geometry to one Na(7), two equivalent Na(3), two equivalent Na(4), and two equivalent Fe(4) atoms. In the seventh O site, O(7) is bonded in a 6-coordinate geometry to one Na(11), one Na(5), two equivalent Na(8), and two equivalent Fe(3) atoms. In the eighth O site, O(8) is bonded to one Na(10), one Na(5), two equivalent Na(3), two equivalent Na(6), and one Fe(1) atom to form distorted corner-sharing ONa6Fe pentagonal bipyramids. In the ninth O site, O(9) is bonded in a 5-coordinate geometry to one Na(10), one Na(12), one Na(3), one Na(9), one Fe(3), and one Fe(4) atom. In the tenth O site, O(10) is bonded in a 7-coordinate geometry to one Na(1), one Na(12), one Na(7), one Na(8), one Na(9), one Fe(4), and one Fe(5) atom. In the eleventh O site, O(11) is bonded to one Na(11), two equivalent Na(2), one Fe(2), and one Fe(5) atom to form corner-sharing ONa3Fe2 trigonal bipyramids. In the twelfth O site, O(12) is bonded in a 6-coordinate geometry to one Na(1), one Na(11), one Na(12), one Na(2), one Na(8), and one Fe(1) atom.