Mg5Ce crystallizes in the monoclinic Cm space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 11-coordinate geometry to one Mg(3), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), and two equivalent Ce(1) atoms. In the second Mg site, Mg(2) is bonded to one Mg(5), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and three equivalent Ce(1) atoms to form MgCe3Mg9 cuboctahedra that share corners with six equivalent Mg(2)Ce3Mg9 cuboctahedra, corners with six equivalent Mg(4)CeMg11 cuboctahedra, edges with two equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with three equivalent Mg(4)CeMg11 cuboctahedra, edges with six equivalent Mg(3)Ce2Mg10 cuboctahedra, faces with two equivalent Mg(2)Ce3Mg9 cuboctahedra, faces with three equivalent Mg(3)Ce2Mg10 cuboctahedra, faces with three equivalent Mg(4)CeMg11 cuboctahedra, and faces with five equivalent Ce(1)Ce2Mg10 cuboctahedra. In the third Mg site, Mg(3) is bonded to one Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(5), three equivalent Mg(4), and two equivalent Ce(1) atoms to form distorted MgCe2Mg10 cuboctahedra that share corners with six equivalent Mg(3)Ce2Mg10 cuboctahedra, corners with six equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with two equivalent Mg(4)CeMg11 cuboctahedra, edges with three equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with six equivalent Mg(2)Ce3Mg9 cuboctahedra, faces with two equivalent Mg(3)Ce2Mg10 cuboctahedra, faces with three equivalent Mg(2)Ce3Mg9 cuboctahedra, faces with three equivalent Ce(1)Ce2Mg10 cuboctahedra, and faces with five equivalent Mg(4)CeMg11 cuboctahedra. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), three equivalent Mg(3), and one Ce(1) atom to form distorted MgCeMg11 cuboctahedra that share corners with six equivalent Mg(2)Ce3Mg9 cuboctahedra, corners with six equivalent Mg(4)CeMg11 cuboctahedra, edges with two equivalent Mg(3)Ce2Mg10 cuboctahedra, edges with three equivalent Mg(2)Ce3Mg9 cuboctahedra, edges with four equivalent Ce(1)Ce2Mg10 cuboctahedra, faces with two equivalent Mg(4)CeMg11 cuboctahedra, faces with three equivalent Mg(2)Ce3Mg9 cuboctahedra, faces with four equivalent Ce(1)Ce2Mg10 cuboctahedra, and faces with five equivalent Mg(3)Ce2Mg10 cuboctahedra. In the fifth Mg site, Mg(5) is bonded in a 11-coordinate geometry to one Mg(2), two equivalent Mg(1), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(5), and two equivalent Ce(1) atoms. Ce(1) is bonded to one Mg(4), two equivalent Mg(1), two equivalent Mg(3), two equivalent Mg(5), three equivalent Mg(2), and two equivalent Ce(1) atoms to form CeCe2Mg10 cuboctahedra that share corners with six equivalent Mg(3)Ce2Mg10 cuboctahedra, corners with six equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with two equivalent Mg(2)Ce3Mg9 cuboctahedra, edges with three equivalent Mg(3)Ce2Mg10 cuboctahedra, edges with four equivalent Mg(4)CeMg11 cuboctahedra, faces with two equivalent Ce(1)Ce2Mg10 cuboctahedra, faces with three equivalent Mg(3)Ce2Mg10 cuboctahedra, faces with four equivalent Mg(4)CeMg11 cuboctahedra, and faces with five equivalent Mg(2)Ce3Mg9 cuboctahedra.
Mg5Ce crystallizes in the monoclinic Cm space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 11-coordinate geometry to one Mg(3), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), and two equivalent Ce(1) atoms. The Mg(1)-Mg(3) bond length is 3.14 Å. Both Mg(1)-Mg(1) bond lengths are 3.14 Å. Both Mg(1)-Mg(2) bond lengths are 3.29 Å. Both Mg(1)-Mg(4) bond lengths are 3.29 Å. Both Mg(1)-Mg(5) bond lengths are 3.27 Å. Both Mg(1)-Ce(1) bond lengths are 3.33 Å. In the second Mg site, Mg(2) is bonded to one Mg(5), two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), and three equivalent Ce(1) atoms to form MgCe3Mg9 cuboctahedra that share corners with six equivalent Mg(2)Ce3Mg9 cuboctahedra, corners with six equivalent Mg(4)CeMg11 cuboctahedra, edges with two equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with three equivalent Mg(4)CeMg11 cuboctahedra, edges with six equivalent Mg(3)Ce2Mg10 cuboctahedra, faces with two equivalent Mg(2)Ce3Mg9 cuboctahedra, faces with three equivalent Mg(3)Ce2Mg10 cuboctahedra, faces with three equivalent Mg(4)CeMg11 cuboctahedra, and faces with five equivalent Ce(1)Ce2Mg10 cuboctahedra. The Mg(2)-Mg(5) bond length is 3.34 Å. Both Mg(2)-Mg(2) bond lengths are 3.14 Å. Both Mg(2)-Mg(3) bond lengths are 3.23 Å. Both Mg(2)-Mg(4) bond lengths are 3.34 Å. There are two shorter (3.43 Å) and one longer (3.45 Å) Mg(2)-Ce(1) bond length. In the third Mg site, Mg(3) is bonded to one Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(5), three equivalent Mg(4), and two equivalent Ce(1) atoms to form distorted MgCe2Mg10 cuboctahedra that share corners with six equivalent Mg(3)Ce2Mg10 cuboctahedra, corners with six equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with two equivalent Mg(4)CeMg11 cuboctahedra, edges with three equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with six equivalent Mg(2)Ce3Mg9 cuboctahedra, faces with two equivalent Mg(3)Ce2Mg10 cuboctahedra, faces with three equivalent Mg(2)Ce3Mg9 cuboctahedra, faces with three equivalent Ce(1)Ce2Mg10 cuboctahedra, and faces with five equivalent Mg(4)CeMg11 cuboctahedra. Both Mg(3)-Mg(3) bond lengths are 3.14 Å. Both Mg(3)-Mg(5) bond lengths are 3.16 Å. There are two shorter (3.43 Å) and one longer (3.44 Å) Mg(3)-Mg(4) bond length. Both Mg(3)-Ce(1) bond lengths are 3.40 Å. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), three equivalent Mg(3), and one Ce(1) atom to form distorted MgCeMg11 cuboctahedra that share corners with six equivalent Mg(2)Ce3Mg9 cuboctahedra, corners with six equivalent Mg(4)CeMg11 cuboctahedra, edges with two equivalent Mg(3)Ce2Mg10 cuboctahedra, edges with three equivalent Mg(2)Ce3Mg9 cuboctahedra, edges with four equivalent Ce(1)Ce2Mg10 cuboctahedra, faces with two equivalent Mg(4)CeMg11 cuboctahedra, faces with three equivalent Mg(2)Ce3Mg9 cuboctahedra, faces with four equivalent Ce(1)Ce2Mg10 cuboctahedra, and faces with five equivalent Mg(3)Ce2Mg10 cuboctahedra. Both Mg(4)-Mg(4) bond lengths are 3.14 Å. Both Mg(4)-Mg(5) bond lengths are 3.23 Å. The Mg(4)-Ce(1) bond length is 3.31 Å. In the fifth Mg site, Mg(5) is bonded in a 11-coordinate geometry to one Mg(2), two equivalent Mg(1), two equivalent Mg(3), two equivalent Mg(4), two equivalent Mg(5), and two equivalent Ce(1) atoms. Both Mg(5)-Mg(5) bond lengths are 3.14 Å. Both Mg(5)-Ce(1) bond lengths are 3.35 Å. Ce(1) is bonded to one Mg(4), two equivalent Mg(1), two equivalent Mg(3), two equivalent Mg(5), three equivalent Mg(2), and two equivalent Ce(1) atoms to form CeCe2Mg10 cuboctahedra that share corners with six equivalent Mg(3)Ce2Mg10 cuboctahedra, corners with six equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with two equivalent Mg(2)Ce3Mg9 cuboctahedra, edges with three equivalent Mg(3)Ce2Mg10 cuboctahedra, edges with four equivalent Mg(4)CeMg11 cuboctahedra, faces with two equivalent Ce(1)Ce2Mg10 cuboctahedra, faces with three equivalent Mg(3)Ce2Mg10 cuboctahedra, faces with four equivalent Mg(4)CeMg11 cuboctahedra, and faces with five equivalent Mg(2)Ce3Mg9 cuboctahedra. Both Ce(1)-Ce(1) bond lengths are 3.14 Å.