MgCo4NiO8 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Co(3)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-13°. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with six equivalent Co(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-14°. In the second Co site, Co(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with six equivalent Co(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-14°. In the third Co site, Co(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-13°. In the fourth Co site, Co(4) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form CoO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. Ni(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and edges with two equivalent Co(4)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Co(3), one Co(4), and one Ni(1) atom. In the second O site, O(2) is bonded in a see-saw-like geometry to one Co(1), one Co(2), one Co(4), and one Ni(1) atom. In the third O site, O(3) is bonded to one Mg(1), one Co(1), one Co(2), one Co(3), and one Ni(1) atom to form OMgCo3Ni square pyramids that share corners with five equivalent O(3)MgCo3Ni square pyramids and edges with four equivalent O(4)MgCo4 square pyramids. In the fourth O site, O(4) is bonded to one Mg(1), one Co(1), one Co(2), one Co(3), and one Co(4) atom to form OMgCo4 square pyramids that share corners with five equivalent O(4)MgCo4 square pyramids and edges with four equivalent O(3)MgCo3Ni square pyramids.
MgCo4NiO8 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Co(3)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-13°. Both Mg(1)-O(1) bond lengths are 2.14 Å. Both Mg(1)-O(3) bond lengths are 2.13 Å. Both Mg(1)-O(4) bond lengths are 2.10 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with six equivalent Co(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-14°. Both Co(1)-O(2) bond lengths are 2.12 Å. Both Co(1)-O(3) bond lengths are 2.15 Å. Both Co(1)-O(4) bond lengths are 2.12 Å. In the second Co site, Co(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with six equivalent Co(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-14°. Both Co(2)-O(2) bond lengths are 2.00 Å. Both Co(2)-O(3) bond lengths are 2.03 Å. Both Co(2)-O(4) bond lengths are 2.08 Å. In the third Co site, Co(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-13°. Both Co(3)-O(1) bond lengths are 1.97 Å. Both Co(3)-O(3) bond lengths are 2.07 Å. Both Co(3)-O(4) bond lengths are 2.08 Å. In the fourth Co site, Co(4) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form CoO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. Both Co(4)-O(1) bond lengths are 1.95 Å. Both Co(4)-O(2) bond lengths are 1.93 Å. Both Co(4)-O(4) bond lengths are 1.92 Å. Ni(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and edges with two equivalent Co(4)O6 octahedra. Both Ni(1)-O(1) bond lengths are 1.92 Å. Both Ni(1)-O(2) bond lengths are 1.92 Å. Both Ni(1)-O(3) bond lengths are 2.07 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Co(3), one Co(4), and one Ni(1) atom. In the second O site, O(2) is bonded in a see-saw-like geometry to one Co(1), one Co(2), one Co(4), and one Ni(1) atom. In the third O site, O(3) is bonded to one Mg(1), one Co(1), one Co(2), one Co(3), and one Ni(1) atom to form OMgCo3Ni square pyramids that share corners with five equivalent O(3)MgCo3Ni square pyramids and edges with four equivalent O(4)MgCo4 square pyramids. In the fourth O site, O(4) is bonded to one Mg(1), one Co(1), one Co(2), one Co(3), and one Co(4) atom to form OMgCo4 square pyramids that share corners with five equivalent O(4)MgCo4 square pyramids and edges with four equivalent O(3)MgCo3Ni square pyramids.