Co3NiO8 is Rutile-derived structured and crystallizes in the hexagonal P6_3mc space group. Co(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form CoO6 octahedra that share corners with two equivalent Ni(1)O6 octahedra,  an edgeedge with one Ni(1)O6 octahedra, and edges with four equivalent Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. Ni(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Co(1)O6 octahedra and edges with three equivalent Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to two equivalent Co(1) and one Ni(1) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to two equivalent Co(1) and one Ni(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to three equivalent Co(1) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to three equivalent Co(1) atoms.
Co3NiO8 is Rutile-derived structured and crystallizes in the hexagonal P6_3mc space group. Co(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form CoO6 octahedra that share corners with two equivalent Ni(1)O6 octahedra,  an edgeedge with one Ni(1)O6 octahedra, and edges with four equivalent Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. The Co(1)-O(3) bond length is 1.87 Å. The Co(1)-O(4) bond length is 1.90 Å. Both Co(1)-O(1) bond lengths are 1.84 Å. Both Co(1)-O(2) bond lengths are 1.90 Å. Ni(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Co(1)O6 octahedra and edges with three equivalent Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. All Ni(1)-O(1) bond lengths are 1.92 Å. All Ni(1)-O(2) bond lengths are 1.87 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to two equivalent Co(1) and one Ni(1) atom. In the second O site, O(2) is bonded in a distorted T-shaped geometry to two equivalent Co(1) and one Ni(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to three equivalent Co(1) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to three equivalent Co(1) atoms.