Mg3Ce crystallizes in the orthorhombic Pmm2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and four equivalent Ce(1) atoms to form MgCe4Mg8 cuboctahedra that share corners with eight equivalent Ce(1)Ce2Mg10 cuboctahedra, corners with ten equivalent Mg(1)Ce4Mg8 cuboctahedra, edges with two equivalent Mg(1)Ce4Mg8 cuboctahedra, edges with four equivalent Ce(1)Ce2Mg10 cuboctahedra, faces with four equivalent Mg(1)Ce4Mg8 cuboctahedra, and faces with four equivalent Ce(1)Ce2Mg10 cuboctahedra. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), and four equivalent Ce(1) atoms. In the third Mg site, Mg(3) is bonded in a 10-coordinate geometry to two equivalent Mg(2), two equivalent Mg(3), four equivalent Mg(1), and two equivalent Ce(1) atoms. Ce(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Ce(1) atoms to form CeCe2Mg10 cuboctahedra that share corners with eight equivalent Mg(1)Ce4Mg8 cuboctahedra, corners with ten equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with two equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with four equivalent Mg(1)Ce4Mg8 cuboctahedra, faces with four equivalent Mg(1)Ce4Mg8 cuboctahedra, and faces with four equivalent Ce(1)Ce2Mg10 cuboctahedra.
Mg3Ce crystallizes in the orthorhombic Pmm2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and four equivalent Ce(1) atoms to form MgCe4Mg8 cuboctahedra that share corners with eight equivalent Ce(1)Ce2Mg10 cuboctahedra, corners with ten equivalent Mg(1)Ce4Mg8 cuboctahedra, edges with two equivalent Mg(1)Ce4Mg8 cuboctahedra, edges with four equivalent Ce(1)Ce2Mg10 cuboctahedra, faces with four equivalent Mg(1)Ce4Mg8 cuboctahedra, and faces with four equivalent Ce(1)Ce2Mg10 cuboctahedra. Both Mg(1)-Mg(1) bond lengths are 3.13 Å. Both Mg(1)-Mg(2) bond lengths are 3.22 Å. All Mg(1)-Mg(3) bond lengths are 3.28 Å. There are two shorter (3.47 Å) and two longer (3.50 Å) Mg(1)-Ce(1) bond lengths. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), and four equivalent Ce(1) atoms. Both Mg(2)-Mg(2) bond lengths are 3.13 Å. Both Mg(2)-Mg(3) bond lengths are 3.32 Å. All Mg(2)-Ce(1) bond lengths are 3.34 Å. In the third Mg site, Mg(3) is bonded in a 10-coordinate geometry to two equivalent Mg(2), two equivalent Mg(3), four equivalent Mg(1), and two equivalent Ce(1) atoms. Both Mg(3)-Mg(3) bond lengths are 3.13 Å. Both Mg(3)-Ce(1) bond lengths are 3.33 Å. Ce(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Ce(1) atoms to form CeCe2Mg10 cuboctahedra that share corners with eight equivalent Mg(1)Ce4Mg8 cuboctahedra, corners with ten equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with two equivalent Ce(1)Ce2Mg10 cuboctahedra, edges with four equivalent Mg(1)Ce4Mg8 cuboctahedra, faces with four equivalent Mg(1)Ce4Mg8 cuboctahedra, and faces with four equivalent Ce(1)Ce2Mg10 cuboctahedra. Both Ce(1)-Ce(1) bond lengths are 3.13 Å.