Mg6CeBO8 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 Ce(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 MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with four equivalent B(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 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 distorted 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 Ce(1)O6 octahedra, edges with two equivalent B(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-15°. Ce(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form CeO6 octahedra that share corners with two equivalent B(1)O6 octahedra, corners with four equivalent Ce(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. B(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form distorted BO6 octahedra that share corners with two equivalent Ce(1)O6 octahedra, corners with four equivalent B(1)O6 octahedra, edges with four equivalent Mg(2)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. There are four inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mg(3), one Ce(1), and one B(1) atom to form distorted OCeMg4B square pyramids that share corners with six equivalent O(1)CeMg4B square pyramids, edges with four equivalent O(3)Ce2Mg4 octahedra, edges with four equivalent O(4)Mg4B2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. 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)Ce2Mg4 octahedra, edges with four equivalent O(4)Mg4B2 octahedra, and edges with four equivalent O(1)CeMg4B square pyramids. The corner-sharing octahedral tilt angles range from 0-12°. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Mg(3), and two equivalent Ce(1) atoms to form OCe2Mg4 octahedra that share corners with two equivalent O(4)Mg4B2 octahedra, corners with four equivalent O(3)Ce2Mg4 octahedra, edges with four equivalent O(3)Ce2Mg4 octahedra, edges with four equivalent O(2)Mg6 octahedra, and edges with four equivalent O(1)CeMg4B square pyramids. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(2), two equivalent Mg(3), and two equivalent B(1) atoms to form distorted OMg4B2 octahedra that share corners with two equivalent O(3)Ce2Mg4 octahedra, corners with four equivalent O(4)Mg4B2 octahedra, edges with four equivalent O(4)Mg4B2 octahedra, edges with four equivalent O(2)Mg6 octahedra, and edges with four equivalent O(1)CeMg4B square pyramids. The corner-sharing octahedra are not tilted.
Mg6CeBO8 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 Ce(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 2.34 Å. All Mg(1)-O(3) bond lengths are 2.23 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with four equivalent B(1)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(2)-O(2) bond lengths are 2.24 Å. All Mg(2)-O(4) bond lengths are 2.23 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 distorted 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 Ce(1)O6 octahedra, edges with two equivalent B(1)O6 octahedra, and edges with four equivalent Mg(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-15°. The Mg(3)-O(3) bond length is 2.57 Å. The Mg(3)-O(4) bond length is 2.00 Å. Both Mg(3)-O(1) bond lengths are 2.25 Å. Both Mg(3)-O(2) bond lengths are 2.24 Å. Ce(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form CeO6 octahedra that share corners with two equivalent B(1)O6 octahedra, corners with four equivalent Ce(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 Ce(1)-O(1) bond lengths are 2.29 Å. All Ce(1)-O(3) bond lengths are 2.23 Å. B(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form distorted BO6 octahedra that share corners with two equivalent Ce(1)O6 octahedra, corners with four equivalent B(1)O6 octahedra, edges with four equivalent Mg(2)O6 octahedra, and edges with eight equivalent Mg(3)O6 octahedra. The corner-sharing octahedra are not tilted. Both B(1)-O(1) bond lengths are 2.28 Å. All B(1)-O(4) bond lengths are 2.23 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mg(3), one Ce(1), and one B(1) atom to form distorted OCeMg4B square pyramids that share corners with six equivalent O(1)CeMg4B square pyramids, edges with four equivalent O(3)Ce2Mg4 octahedra, edges with four equivalent O(4)Mg4B2 octahedra, and edges with four equivalent O(2)Mg6 octahedra. 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)Ce2Mg4 octahedra, edges with four equivalent O(4)Mg4B2 octahedra, and edges with four equivalent O(1)CeMg4B square pyramids. The corner-sharing octahedral tilt angles range from 0-12°. In the third O site, O(3) is bonded to two equivalent Mg(1), two equivalent Mg(3), and two equivalent Ce(1) atoms to form OCe2Mg4 octahedra that share corners with two equivalent O(4)Mg4B2 octahedra, corners with four equivalent O(3)Ce2Mg4 octahedra, edges with four equivalent O(3)Ce2Mg4 octahedra, edges with four equivalent O(2)Mg6 octahedra, and edges with four equivalent O(1)CeMg4B square pyramids. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(2), two equivalent Mg(3), and two equivalent B(1) atoms to form distorted OMg4B2 octahedra that share corners with two equivalent O(3)Ce2Mg4 octahedra, corners with four equivalent O(4)Mg4B2 octahedra, edges with four equivalent O(4)Mg4B2 octahedra, edges with four equivalent O(2)Mg6 octahedra, and edges with four equivalent O(1)CeMg4B square pyramids. The corner-sharing octahedra are not tilted.