BaMg6CO8 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form BaO6 octahedra that share corners with four equivalent Ba(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. 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 Ba(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 Ba(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-8°. C(1) is bonded in a linear geometry to two equivalent O(1) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ba(1), four equivalent Mg(3), and one C(1) atom to form OBaMg4C octahedra that share corners with six equivalent O(1)BaMg4C octahedra, edges with four equivalent O(3)Ba2Mg4 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-8°. 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)Ba2Mg4 octahedra, and edges with four equivalent O(1)BaMg4C octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the third O site, O(3) is bonded to two equivalent Ba(1), two equivalent Mg(1), and two equivalent Mg(3) atoms to form OBa2Mg4 octahedra that share corners with four equivalent O(3)Ba2Mg4 octahedra, edges with four equivalent O(3)Ba2Mg4 octahedra, edges with four equivalent O(1)BaMg4C 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.
BaMg6CO8 crystallizes in the tetragonal P4/mmm space group. Ba(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form BaO6 octahedra that share corners with four equivalent Ba(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 Ba(1)-O(1) bond lengths are 2.49 Å. All Ba(1)-O(3) bond lengths are 2.33 Å. 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 Ba(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 2.19 Å. All Mg(1)-O(3) bond lengths are 2.33 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 2.14 Å. All Mg(2)-O(4) bond lengths are 2.33 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 Ba(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-8°. The Mg(3)-O(3) bond length is 2.33 Å. The Mg(3)-O(4) bond length is 2.00 Å. Both Mg(3)-O(1) bond lengths are 2.33 Å. Both Mg(3)-O(2) bond lengths are 2.33 Å. C(1) is bonded in a linear geometry to two equivalent O(1) atoms. Both C(1)-O(1) bond lengths are 1.85 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ba(1), four equivalent Mg(3), and one C(1) atom to form OBaMg4C octahedra that share corners with six equivalent O(1)BaMg4C octahedra, edges with four equivalent O(3)Ba2Mg4 octahedra, and edges with four equivalent O(2)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-8°. 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)Ba2Mg4 octahedra, and edges with four equivalent O(1)BaMg4C octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the third O site, O(3) is bonded to two equivalent Ba(1), two equivalent Mg(1), and two equivalent Mg(3) atoms to form OBa2Mg4 octahedra that share corners with four equivalent O(3)Ba2Mg4 octahedra, edges with four equivalent O(3)Ba2Mg4 octahedra, edges with four equivalent O(1)BaMg4C 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.