Na(FeO2)2 crystallizes in the monoclinic P2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form edge-sharing FeO6 octahedra. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form edge-sharing FeO6 octahedra. In the third Fe site, Fe(3) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form edge-sharing FeO6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Fe(2), and two equivalent Fe(1) atoms to form ONa2Fe3 trigonal bipyramids that share corners with two equivalent O(2)Na2Fe3 trigonal bipyramids, corners with three equivalent O(1)Na2Fe3 trigonal bipyramids, corners with two equivalent O(3)NaFe3 trigonal pyramids, corners with two equivalent O(4)NaFe3 trigonal pyramids,  an edgeedge with one O(1)Na2Fe3 trigonal bipyramid, edges with three equivalent O(2)Na2Fe3 trigonal bipyramids, edges with two equivalent O(3)NaFe3 trigonal pyramids, and edges with two equivalent O(4)NaFe3 trigonal pyramids. In the second O site, O(2) is bonded to one Na(1), one Na(2), one Fe(3), and two equivalent Fe(1) atoms to form ONa2Fe3 trigonal bipyramids that share corners with two equivalent O(1)Na2Fe3 trigonal bipyramids, corners with three equivalent O(2)Na2Fe3 trigonal bipyramids, corners with two equivalent O(3)NaFe3 trigonal pyramids, corners with two equivalent O(4)NaFe3 trigonal pyramids,  an edgeedge with one O(2)Na2Fe3 trigonal bipyramid, edges with three equivalent O(1)Na2Fe3 trigonal bipyramids, edges with two equivalent O(3)NaFe3 trigonal pyramids, and edges with two equivalent O(4)NaFe3 trigonal pyramids. In the third O site, O(3) is bonded to one Na(2), one Fe(1), one Fe(2), and one Fe(3) atom to form distorted ONaFe3 trigonal pyramids that share corners with two equivalent O(1)Na2Fe3 trigonal bipyramids, corners with two equivalent O(2)Na2Fe3 trigonal bipyramids, corners with three equivalent O(3)NaFe3 trigonal pyramids, corners with three equivalent O(4)NaFe3 trigonal pyramids, edges with two equivalent O(1)Na2Fe3 trigonal bipyramids, edges with two equivalent O(2)Na2Fe3 trigonal bipyramids, and  an edgeedge with one O(4)NaFe3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Na(1), one Fe(1), one Fe(2), and one Fe(3) atom to form ONaFe3 trigonal pyramids that share corners with two equivalent O(1)Na2Fe3 trigonal bipyramids, corners with two equivalent O(2)Na2Fe3 trigonal bipyramids, corners with three equivalent O(3)NaFe3 trigonal pyramids, corners with three equivalent O(4)NaFe3 trigonal pyramids, edges with two equivalent O(1)Na2Fe3 trigonal bipyramids, edges with two equivalent O(2)Na2Fe3 trigonal bipyramids, and  an edgeedge with one O(3)NaFe3 trigonal pyramid.
Na(FeO2)2 crystallizes in the monoclinic P2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms. Both Na(1)-O(1) bond lengths are 2.56 Å. Both Na(1)-O(2) bond lengths are 2.55 Å. Both Na(1)-O(4) bond lengths are 2.41 Å. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Both Na(2)-O(1) bond lengths are 2.56 Å. Both Na(2)-O(2) bond lengths are 2.57 Å. Both Na(2)-O(3) bond lengths are 2.42 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form edge-sharing FeO6 octahedra. The Fe(1)-O(3) bond length is 2.00 Å. The Fe(1)-O(4) bond length is 2.01 Å. There is one shorter (2.03 Å) and one longer (2.08 Å) Fe(1)-O(1) bond length. There is one shorter (1.99 Å) and one longer (2.05 Å) Fe(1)-O(2) bond length. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form edge-sharing FeO6 octahedra. Both Fe(2)-O(1) bond lengths are 1.99 Å. Both Fe(2)-O(3) bond lengths are 1.96 Å. Both Fe(2)-O(4) bond lengths are 2.00 Å. In the third Fe site, Fe(3) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form edge-sharing FeO6 octahedra. Both Fe(3)-O(2) bond lengths are 2.03 Å. Both Fe(3)-O(3) bond lengths are 2.04 Å. Both Fe(3)-O(4) bond lengths are 2.03 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Fe(2), and two equivalent Fe(1) atoms to form ONa2Fe3 trigonal bipyramids that share corners with two equivalent O(2)Na2Fe3 trigonal bipyramids, corners with three equivalent O(1)Na2Fe3 trigonal bipyramids, corners with two equivalent O(3)NaFe3 trigonal pyramids, corners with two equivalent O(4)NaFe3 trigonal pyramids,  an edgeedge with one O(1)Na2Fe3 trigonal bipyramid, edges with three equivalent O(2)Na2Fe3 trigonal bipyramids, edges with two equivalent O(3)NaFe3 trigonal pyramids, and edges with two equivalent O(4)NaFe3 trigonal pyramids. In the second O site, O(2) is bonded to one Na(1), one Na(2), one Fe(3), and two equivalent Fe(1) atoms to form ONa2Fe3 trigonal bipyramids that share corners with two equivalent O(1)Na2Fe3 trigonal bipyramids, corners with three equivalent O(2)Na2Fe3 trigonal bipyramids, corners with two equivalent O(3)NaFe3 trigonal pyramids, corners with two equivalent O(4)NaFe3 trigonal pyramids,  an edgeedge with one O(2)Na2Fe3 trigonal bipyramid, edges with three equivalent O(1)Na2Fe3 trigonal bipyramids, edges with two equivalent O(3)NaFe3 trigonal pyramids, and edges with two equivalent O(4)NaFe3 trigonal pyramids. In the third O site, O(3) is bonded to one Na(2), one Fe(1), one Fe(2), and one Fe(3) atom to form distorted ONaFe3 trigonal pyramids that share corners with two equivalent O(1)Na2Fe3 trigonal bipyramids, corners with two equivalent O(2)Na2Fe3 trigonal bipyramids, corners with three equivalent O(3)NaFe3 trigonal pyramids, corners with three equivalent O(4)NaFe3 trigonal pyramids, edges with two equivalent O(1)Na2Fe3 trigonal bipyramids, edges with two equivalent O(2)Na2Fe3 trigonal bipyramids, and  an edgeedge with one O(4)NaFe3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Na(1), one Fe(1), one Fe(2), and one Fe(3) atom to form ONaFe3 trigonal pyramids that share corners with two equivalent O(1)Na2Fe3 trigonal bipyramids, corners with two equivalent O(2)Na2Fe3 trigonal bipyramids, corners with three equivalent O(3)NaFe3 trigonal pyramids, corners with three equivalent O(4)NaFe3 trigonal pyramids, edges with two equivalent O(1)Na2Fe3 trigonal bipyramids, edges with two equivalent O(2)Na2Fe3 trigonal bipyramids, and  an edgeedge with one O(3)NaFe3 trigonal pyramid.