Ca7Mg(CoO3)8 is (Cubic) Perovskite-derived structured and crystallizes in the cubic Pm-3m space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form CaO12 cuboctahedra that share corners with four equivalent Ca(3)O12 cuboctahedra, corners with eight equivalent Ca(1)O12 cuboctahedra, faces with two equivalent Mg(1)O12 cuboctahedra, faces with four equivalent Ca(2)O12 cuboctahedra, and faces with eight equivalent Co(1)O6 octahedra. In the second Ca site, Ca(2) is bonded to four equivalent O(1) and eight equivalent O(2) atoms to form CaO12 cuboctahedra that share corners with four equivalent Mg(1)O12 cuboctahedra, corners with eight equivalent Ca(2)O12 cuboctahedra, faces with two equivalent Ca(3)O12 cuboctahedra, faces with four equivalent Ca(1)O12 cuboctahedra, and faces with eight equivalent Co(1)O6 octahedra. In the third Ca site, Ca(3) is bonded to twelve equivalent O(2) atoms to form CaO12 cuboctahedra that share corners with twelve equivalent Ca(1)O12 cuboctahedra, faces with six equivalent Ca(2)O12 cuboctahedra, and faces with eight equivalent Co(1)O6 octahedra. Mg(1) is bonded to twelve equivalent O(1) atoms to form MgO12 cuboctahedra that share corners with twelve equivalent Ca(2)O12 cuboctahedra, faces with six equivalent Ca(1)O12 cuboctahedra, and faces with eight equivalent Co(1)O6 octahedra. Co(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form CoO6 octahedra that share corners with six equivalent Co(1)O6 octahedra,  a faceface with one Ca(3)O12 cuboctahedra,  a faceface with one Mg(1)O12 cuboctahedra, faces with three equivalent Ca(1)O12 cuboctahedra, and faces with three equivalent Ca(2)O12 cuboctahedra. The corner-sharing octahedra are not tilted. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one Ca(2), two equivalent Ca(1), one Mg(1), and two equivalent Co(1) atoms. In the second O site, O(2) is bonded to one Ca(1), one Ca(3), two equivalent Ca(2), and two equivalent Co(1) atoms to form a mixture of distorted edge, face, and corner-sharing OCa4Co2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°.
Ca7Mg(CoO3)8 is (Cubic) Perovskite-derived structured and crystallizes in the cubic Pm-3m space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to four equivalent O(2) and eight equivalent O(1) atoms to form CaO12 cuboctahedra that share corners with four equivalent Ca(3)O12 cuboctahedra, corners with eight equivalent Ca(1)O12 cuboctahedra, faces with two equivalent Mg(1)O12 cuboctahedra, faces with four equivalent Ca(2)O12 cuboctahedra, and faces with eight equivalent Co(1)O6 octahedra. All Ca(1)-O(2) bond lengths are 2.67 Å. All Ca(1)-O(1) bond lengths are 2.67 Å. In the second Ca site, Ca(2) is bonded to four equivalent O(1) and eight equivalent O(2) atoms to form CaO12 cuboctahedra that share corners with four equivalent Mg(1)O12 cuboctahedra, corners with eight equivalent Ca(2)O12 cuboctahedra, faces with two equivalent Ca(3)O12 cuboctahedra, faces with four equivalent Ca(1)O12 cuboctahedra, and faces with eight equivalent Co(1)O6 octahedra. All Ca(2)-O(1) bond lengths are 2.68 Å. All Ca(2)-O(2) bond lengths are 2.67 Å. In the third Ca site, Ca(3) is bonded to twelve equivalent O(2) atoms to form CaO12 cuboctahedra that share corners with twelve equivalent Ca(1)O12 cuboctahedra, faces with six equivalent Ca(2)O12 cuboctahedra, and faces with eight equivalent Co(1)O6 octahedra. All Ca(3)-O(2) bond lengths are 2.67 Å. Mg(1) is bonded to twelve equivalent O(1) atoms to form MgO12 cuboctahedra that share corners with twelve equivalent Ca(2)O12 cuboctahedra, faces with six equivalent Ca(1)O12 cuboctahedra, and faces with eight equivalent Co(1)O6 octahedra. All Mg(1)-O(1) bond lengths are 2.66 Å. Co(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form CoO6 octahedra that share corners with six equivalent Co(1)O6 octahedra,  a faceface with one Ca(3)O12 cuboctahedra,  a faceface with one Mg(1)O12 cuboctahedra, faces with three equivalent Ca(1)O12 cuboctahedra, and faces with three equivalent Ca(2)O12 cuboctahedra. The corner-sharing octahedra are not tilted. All Co(1)-O(1) bond lengths are 1.88 Å. All Co(1)-O(2) bond lengths are 1.89 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one Ca(2), two equivalent Ca(1), one Mg(1), and two equivalent Co(1) atoms. In the second O site, O(2) is bonded to one Ca(1), one Ca(3), two equivalent Ca(2), and two equivalent Co(1) atoms to form a mixture of distorted edge, face, and corner-sharing OCa4Co2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°.