Mg6CdCO8 crystallizes in the tetragonal P4/mmm space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, edges with four equivalent Cd(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. In the second Mg site, Mg(2) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. In the third Mg site, Mg(3) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Cd(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. Cd(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form CdO6 octahedra that share corners with four equivalent Cd(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. C(1) is bonded in a distorted linear geometry to two equivalent O(1) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mg(3), one Cd(1), and one C(1) atom to form OMg4CdC octahedra that share corners with six equivalent O(1)Mg4CdC octahedra, edges with four equivalent O(3)Mg4Cd2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and four equivalent Mg(3) atoms to form OMg6 octahedra that share corners with six equivalent O(2)Mg6 octahedra, edges with four equivalent O(3)Mg4Cd2 octahedra, and edges with four equivalent O(1)Mg4CdC octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Mg(3), and two equivalent Cd(1) atoms to form OMg4Cd2 octahedra that share corners with four equivalent O(3)Mg4Cd2 octahedra, edges with four equivalent O(3)Mg4Cd2 octahedra, edges with four equivalent O(1)Mg4CdC octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded in a square co-planar geometry to two equivalent Mg(2) and two equivalent Mg(3) atoms.
Mg6CdCO8 crystallizes in the tetragonal P4/mmm space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, edges with four equivalent Cd(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(1)-O(2) bond lengths are 2.17 Å. All Mg(1)-O(3) bond lengths are 2.17 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(2)-O(2) bond lengths are 2.15 Å. All Mg(2)-O(4) bond lengths are 2.17 Å. In the third Mg site, Mg(3) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Mg(3)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with two equivalent Cd(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. The Mg(3)-O(3) bond length is 2.24 Å. The Mg(3)-O(4) bond length is 2.08 Å. Both Mg(3)-O(1) bond lengths are 2.17 Å. Both Mg(3)-O(2) bond lengths are 2.17 Å. Cd(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form CdO6 octahedra that share corners with four equivalent Cd(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both Cd(1)-O(1) bond lengths are 2.32 Å. All Cd(1)-O(3) bond lengths are 2.17 Å. C(1) is bonded in a distorted linear geometry to two equivalent O(1) atoms. Both C(1)-O(1) bond lengths are 2.00 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mg(3), one Cd(1), and one C(1) atom to form OMg4CdC octahedra that share corners with six equivalent O(1)Mg4CdC octahedra, edges with four equivalent O(3)Mg4Cd2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and four equivalent Mg(3) atoms to form OMg6 octahedra that share corners with six equivalent O(2)Mg6 octahedra, edges with four equivalent O(3)Mg4Cd2 octahedra, and edges with four equivalent O(1)Mg4CdC octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Mg(3), and two equivalent Cd(1) atoms to form OMg4Cd2 octahedra that share corners with four equivalent O(3)Mg4Cd2 octahedra, edges with four equivalent O(3)Mg4Cd2 octahedra, edges with four equivalent O(1)Mg4CdC octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded in a square co-planar geometry to two equivalent Mg(2) and two equivalent Mg(3) atoms.