Na4(CoO2)7 crystallizes in the hexagonal P6_3/m space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to six equivalent O(3) 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 two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), two equivalent O(3), and three equivalent O(2) atoms to form edge-sharing CoO6 octahedra. In the second Co site, Co(2) is bonded to six equivalent O(3) atoms to form edge-sharing CoO6 octahedra. There are three inequivalent O sites. In the first O site, O(3) is bonded to one Na(1), one Na(2), one Co(2), and two equivalent Co(1) atoms to form distorted ONa2Co3 trigonal bipyramids that share corners with two equivalent O(1)Na3Co3 octahedra, corners with three equivalent O(3)Na2Co3 trigonal bipyramids, corners with four equivalent O(2)NaCo3 trigonal pyramids,  an edgeedge with one O(1)Na3Co3 octahedra, edges with five equivalent O(3)Na2Co3 trigonal bipyramids, and edges with two equivalent O(2)NaCo3 trigonal pyramids. The corner-sharing octahedral tilt angles range from 0-52°. In the second O site, O(1) is bonded to three equivalent Na(2) and three equivalent Co(1) atoms to form distorted ONa3Co3 octahedra that share corners with six equivalent O(3)Na2Co3 trigonal bipyramids, corners with three equivalent O(2)NaCo3 trigonal pyramids, edges with three equivalent O(3)Na2Co3 trigonal bipyramids, edges with six equivalent O(2)NaCo3 trigonal pyramids, and  a faceface with one O(1)Na3Co3 octahedra. In the third O site, O(2) is bonded to one Na(2) and three equivalent Co(1) atoms to form ONaCo3 trigonal pyramids that share  a cornercorner with one O(1)Na3Co3 octahedra, corners with four equivalent O(3)Na2Co3 trigonal bipyramids, corners with five equivalent O(2)NaCo3 trigonal pyramids, edges with two equivalent O(1)Na3Co3 octahedra, edges with two equivalent O(3)Na2Co3 trigonal bipyramids, and  an edgeedge with one O(2)NaCo3 trigonal pyramid. The corner-sharing octahedral tilt angles are 44°.
Na4(CoO2)7 crystallizes in the hexagonal P6_3/m space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to six equivalent O(3) atoms. All Na(1)-O(3) bond lengths are 2.43 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 2.62 Å. Both Na(2)-O(2) bond lengths are 2.31 Å. Both Na(2)-O(3) bond lengths are 2.42 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), two equivalent O(3), and three equivalent O(2) atoms to form edge-sharing CoO6 octahedra. The Co(1)-O(1) bond length is 1.93 Å. Both Co(1)-O(3) bond lengths are 1.91 Å. There are two shorter (1.89 Å) and one longer (1.90 Å) Co(1)-O(2) bond length. In the second Co site, Co(2) is bonded to six equivalent O(3) atoms to form edge-sharing CoO6 octahedra. All Co(2)-O(3) bond lengths are 1.92 Å. There are three inequivalent O sites. In the first O site, O(3) is bonded to one Na(1), one Na(2), one Co(2), and two equivalent Co(1) atoms to form distorted ONa2Co3 trigonal bipyramids that share corners with two equivalent O(1)Na3Co3 octahedra, corners with three equivalent O(3)Na2Co3 trigonal bipyramids, corners with four equivalent O(2)NaCo3 trigonal pyramids,  an edgeedge with one O(1)Na3Co3 octahedra, edges with five equivalent O(3)Na2Co3 trigonal bipyramids, and edges with two equivalent O(2)NaCo3 trigonal pyramids. The corner-sharing octahedral tilt angles range from 0-52°. In the second O site, O(1) is bonded to three equivalent Na(2) and three equivalent Co(1) atoms to form distorted ONa3Co3 octahedra that share corners with six equivalent O(3)Na2Co3 trigonal bipyramids, corners with three equivalent O(2)NaCo3 trigonal pyramids, edges with three equivalent O(3)Na2Co3 trigonal bipyramids, edges with six equivalent O(2)NaCo3 trigonal pyramids, and  a faceface with one O(1)Na3Co3 octahedra. In the third O site, O(2) is bonded to one Na(2) and three equivalent Co(1) atoms to form ONaCo3 trigonal pyramids that share  a cornercorner with one O(1)Na3Co3 octahedra, corners with four equivalent O(3)Na2Co3 trigonal bipyramids, corners with five equivalent O(2)NaCo3 trigonal pyramids, edges with two equivalent O(1)Na3Co3 octahedra, edges with two equivalent O(3)Na2Co3 trigonal bipyramids, and  an edgeedge with one O(2)NaCo3 trigonal pyramid. The corner-sharing octahedral tilt angles are 44°.