MgCe2 is beta-derived structured and crystallizes in the trigonal R32 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent Mg(1); three equivalent Ce(2); and six Ce(1,1) atoms to form distorted MgCe9Mg3 cuboctahedra that share corners with six equivalent Ce(2)Ce6Mg6 cuboctahedra; corners with twelve Mg(1,1,1)Ce9Mg3 cuboctahedra; edges with six equivalent Mg(1)Ce9Mg3 cuboctahedra; edges with twelve Ce(1,1)Ce8Mg4 cuboctahedra; faces with four Mg(1,1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; and faces with twelve Ce(1,1)Ce8Mg4 cuboctahedra. In the second Mg site, Mg(1) is bonded to three equivalent Mg(1); three equivalent Ce(2); and six Ce(1,1) atoms to form distorted MgCe9Mg3 cuboctahedra that share corners with six equivalent Ce(2)Ce6Mg6 cuboctahedra; corners with twelve Mg(1,1)Ce9Mg3 cuboctahedra; edges with six equivalent Mg(1)Ce9Mg3 cuboctahedra; edges with twelve Ce(1,1)Ce8Mg4 cuboctahedra; faces with four equivalent Mg(1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; and faces with twelve Ce(1,1)Ce8Mg4 cuboctahedra. In the third Mg site, Mg(1) is bonded to three equivalent Mg(1); three equivalent Ce(2); and six Ce(1,1,1) atoms to form distorted MgCe9Mg3 cuboctahedra that share corners with six equivalent Ce(2)Ce6Mg6 cuboctahedra; corners with twelve Mg(1,1)Ce9Mg3 cuboctahedra; edges with six equivalent Mg(1)Ce9Mg3 cuboctahedra; edges with twelve Ce(1,1,1)Ce8Mg4 cuboctahedra; faces with four equivalent Mg(1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; and faces with twelve Ce(1,1,1)Ce8Mg4 cuboctahedra. There are four inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to four Mg(1,1); two equivalent Ce(2); and six equivalent Ce(1) atoms to form distorted CeCe8Mg4 cuboctahedra that share corners with eighteen Ce(1,1,1)Ce8Mg4 cuboctahedra; edges with four equivalent Ce(2)Ce6Mg6 cuboctahedra; edges with six equivalent Ce(1)Ce8Mg4 cuboctahedra; edges with eight Mg(1,1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; faces with eight Mg(1,1)Ce9Mg3 cuboctahedra; and faces with eight Ce(1,1)Ce8Mg4 cuboctahedra. In the second Ce site, Ce(2) is bonded to six Mg(1,1) and six Ce(1,1) atoms to form CeCe6Mg6 cuboctahedra that share corners with six equivalent Ce(2)Ce6Mg6 cuboctahedra; corners with twelve Mg(1,1)Ce9Mg3 cuboctahedra; edges with six equivalent Ce(2)Ce6Mg6 cuboctahedra; edges with twelve Ce(1,1)Ce8Mg4 cuboctahedra; faces with eight Mg(1,1,1)Ce9Mg3 cuboctahedra; and faces with twelve Ce(1,1)Ce8Mg4 cuboctahedra. In the third Ce site, Ce(1) is bonded to four Mg(1,1); two equivalent Ce(2); and six Ce(1,1) atoms to form distorted CeCe8Mg4 cuboctahedra that share corners with eighteen Ce(1,1)Ce8Mg4 cuboctahedra; edges with four equivalent Ce(2)Ce6Mg6 cuboctahedra; edges with six equivalent Ce(1)Ce8Mg4 cuboctahedra; edges with eight Mg(1,1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; faces with eight Mg(1,1)Ce9Mg3 cuboctahedra; and faces with eight Ce(1,1)Ce8Mg4 cuboctahedra. In the fourth Ce site, Ce(1) is bonded to four Mg(1,1); two equivalent Ce(2); and six Ce(1,1) atoms to form distorted CeCe8Mg4 cuboctahedra that share corners with eighteen Ce(1,1,1)Ce8Mg4 cuboctahedra; edges with four equivalent Ce(2)Ce6Mg6 cuboctahedra; edges with six equivalent Ce(1)Ce8Mg4 cuboctahedra; edges with eight Mg(1,1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; faces with eight Mg(1,1)Ce9Mg3 cuboctahedra; and faces with eight Ce(1,1,1)Ce8Mg4 cuboctahedra.
MgCe2 is beta-derived structured and crystallizes in the trigonal R32 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent Mg(1); three equivalent Ce(2); and six Ce(1,1) atoms to form distorted MgCe9Mg3 cuboctahedra that share corners with six equivalent Ce(2)Ce6Mg6 cuboctahedra; corners with twelve Mg(1,1,1)Ce9Mg3 cuboctahedra; edges with six equivalent Mg(1)Ce9Mg3 cuboctahedra; edges with twelve Ce(1,1)Ce8Mg4 cuboctahedra; faces with four Mg(1,1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; and faces with twelve Ce(1,1)Ce8Mg4 cuboctahedra. All Mg(1)-Mg(1) bond lengths are 3.34 Å. All Mg(1)-Ce(2) bond lengths are 3.34 Å. There are three shorter (3.37 Å) and three longer (3.41 Å) Mg(1)-Ce(1,1) bond lengths. In the second Mg site, Mg(1) is bonded to three equivalent Mg(1); three equivalent Ce(2); and six Ce(1,1) atoms to form distorted MgCe9Mg3 cuboctahedra that share corners with six equivalent Ce(2)Ce6Mg6 cuboctahedra; corners with twelve Mg(1,1)Ce9Mg3 cuboctahedra; edges with six equivalent Mg(1)Ce9Mg3 cuboctahedra; edges with twelve Ce(1,1)Ce8Mg4 cuboctahedra; faces with four equivalent Mg(1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; and faces with twelve Ce(1,1)Ce8Mg4 cuboctahedra. All Mg(1)-Ce(2) bond lengths are 3.34 Å. There are three shorter (3.37 Å) and three longer (3.41 Å) Mg(1)-Ce(1,1) bond lengths. In the third Mg site, Mg(1) is bonded to three equivalent Mg(1); three equivalent Ce(2); and six Ce(1,1,1) atoms to form distorted MgCe9Mg3 cuboctahedra that share corners with six equivalent Ce(2)Ce6Mg6 cuboctahedra; corners with twelve Mg(1,1)Ce9Mg3 cuboctahedra; edges with six equivalent Mg(1)Ce9Mg3 cuboctahedra; edges with twelve Ce(1,1,1)Ce8Mg4 cuboctahedra; faces with four equivalent Mg(1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; and faces with twelve Ce(1,1,1)Ce8Mg4 cuboctahedra. All Mg(1)-Mg(1) bond lengths are 3.34 Å. All Mg(1)-Ce(2) bond lengths are 3.34 Å. There are three shorter (3.37 Å) and three longer (3.41 Å) Mg(1)-Ce(1,1,1) bond lengths. There are four inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to four Mg(1,1); two equivalent Ce(2); and six equivalent Ce(1) atoms to form distorted CeCe8Mg4 cuboctahedra that share corners with eighteen Ce(1,1,1)Ce8Mg4 cuboctahedra; edges with four equivalent Ce(2)Ce6Mg6 cuboctahedra; edges with six equivalent Ce(1)Ce8Mg4 cuboctahedra; edges with eight Mg(1,1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; faces with eight Mg(1,1)Ce9Mg3 cuboctahedra; and faces with eight Ce(1,1)Ce8Mg4 cuboctahedra. Both Ce(1)-Ce(2) bond lengths are 3.46 Å. There are two shorter (3.04 Å) and four longer (3.50 Å) Ce(1)-Ce(1) bond lengths. In the second Ce site, Ce(2) is bonded to six Mg(1,1) and six Ce(1,1) atoms to form CeCe6Mg6 cuboctahedra that share corners with six equivalent Ce(2)Ce6Mg6 cuboctahedra; corners with twelve Mg(1,1)Ce9Mg3 cuboctahedra; edges with six equivalent Ce(2)Ce6Mg6 cuboctahedra; edges with twelve Ce(1,1)Ce8Mg4 cuboctahedra; faces with eight Mg(1,1,1)Ce9Mg3 cuboctahedra; and faces with twelve Ce(1,1)Ce8Mg4 cuboctahedra. Both Ce(2)-Ce(1) bond lengths are 3.46 Å. In the third Ce site, Ce(1) is bonded to four Mg(1,1); two equivalent Ce(2); and six Ce(1,1) atoms to form distorted CeCe8Mg4 cuboctahedra that share corners with eighteen Ce(1,1)Ce8Mg4 cuboctahedra; edges with four equivalent Ce(2)Ce6Mg6 cuboctahedra; edges with six equivalent Ce(1)Ce8Mg4 cuboctahedra; edges with eight Mg(1,1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; faces with eight Mg(1,1)Ce9Mg3 cuboctahedra; and faces with eight Ce(1,1)Ce8Mg4 cuboctahedra. There is one shorter (3.37 Å) and two longer (3.41 Å) Ce(1)-Mg(1) bond lengths. Both Ce(1)-Ce(2) bond lengths are 3.46 Å. There are two shorter (3.04 Å) and four longer (3.50 Å) Ce(1)-Ce(1,1) bond lengths. In the fourth Ce site, Ce(1) is bonded to four Mg(1,1); two equivalent Ce(2); and six Ce(1,1) atoms to form distorted CeCe8Mg4 cuboctahedra that share corners with eighteen Ce(1,1,1)Ce8Mg4 cuboctahedra; edges with four equivalent Ce(2)Ce6Mg6 cuboctahedra; edges with six equivalent Ce(1)Ce8Mg4 cuboctahedra; edges with eight Mg(1,1)Ce9Mg3 cuboctahedra; faces with four equivalent Ce(2)Ce6Mg6 cuboctahedra; faces with eight Mg(1,1)Ce9Mg3 cuboctahedra; and faces with eight Ce(1,1,1)Ce8Mg4 cuboctahedra. There is one shorter (3.04 Å) and two longer (3.50 Å) Ce(1)-Ce(1) bond lengths.