K4(CoO2)7 crystallizes in the hexagonal P6_3/m space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to six 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(1) is bonded to three equivalent K(1) and three equivalent Co(1) atoms to form distorted OK3Co3 octahedra that share corners with three equivalent O(2)KCo3 trigonal pyramids, edges with six equivalent O(2)KCo3 trigonal pyramids, and  a faceface with one O(1)K3Co3 octahedra. In the second O site, O(2) is bonded to one K(1) and three equivalent Co(1) atoms to form distorted OKCo3 trigonal pyramids that share  a cornercorner with one O(1)K3Co3 octahedra, corners with five equivalent O(2)KCo3 trigonal pyramids, edges with two equivalent O(1)K3Co3 octahedra, and  an edgeedge with one O(2)KCo3 trigonal pyramid. The corner-sharing octahedral tilt angles are 44°. In the third O site, O(3) is bonded in a 5-coordinate geometry to one K(1), one K(2), one Co(2), and two equivalent Co(1) atoms.
K4(CoO2)7 crystallizes in the hexagonal P6_3/m space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Both K(1)-O(1) bond lengths are 2.90 Å. Both K(1)-O(2) bond lengths are 2.63 Å. Both K(1)-O(3) bond lengths are 2.83 Å. In the second K site, K(2) is bonded in a 6-coordinate geometry to six equivalent O(3) atoms. All K(2)-O(3) bond lengths are 2.66 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 2.04 Å. There is one shorter (2.02 Å) and one longer (2.10 Å) Co(1)-O(3) bond length. There are a spread of Co(1)-O(2) bond distances ranging from 1.93-2.07 Å. 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 1.89 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to three equivalent K(1) and three equivalent Co(1) atoms to form distorted OK3Co3 octahedra that share corners with three equivalent O(2)KCo3 trigonal pyramids, edges with six equivalent O(2)KCo3 trigonal pyramids, and  a faceface with one O(1)K3Co3 octahedra. In the second O site, O(2) is bonded to one K(1) and three equivalent Co(1) atoms to form distorted OKCo3 trigonal pyramids that share  a cornercorner with one O(1)K3Co3 octahedra, corners with five equivalent O(2)KCo3 trigonal pyramids, edges with two equivalent O(1)K3Co3 octahedra, and  an edgeedge with one O(2)KCo3 trigonal pyramid. The corner-sharing octahedral tilt angles are 44°. In the third O site, O(3) is bonded in a 5-coordinate geometry to one K(1), one K(2), one Co(2), and two equivalent Co(1) atoms.