MgY2 crystallizes in the trigonal R32 space group. Mg(1) is bonded to three equivalent Mg(1), three equivalent Y(2), and six equivalent Y(1) atoms to form MgY9Mg3 cuboctahedra that share corners with six equivalent Y(2)Y6Mg6 cuboctahedra, corners with twelve equivalent Mg(1)Y9Mg3 cuboctahedra, edges with six equivalent Mg(1)Y9Mg3 cuboctahedra, edges with twelve equivalent Y(1)Y8Mg4 cuboctahedra, faces with four equivalent Mg(1)Y9Mg3 cuboctahedra, faces with four equivalent Y(2)Y6Mg6 cuboctahedra, and faces with twelve equivalent Y(1)Y8Mg4 cuboctahedra. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to four equivalent Mg(1), two equivalent Y(2), and six equivalent Y(1) atoms to form YY8Mg4 cuboctahedra that share corners with eighteen equivalent Y(1)Y8Mg4 cuboctahedra, edges with four equivalent Y(2)Y6Mg6 cuboctahedra, edges with six equivalent Y(1)Y8Mg4 cuboctahedra, edges with eight equivalent Mg(1)Y9Mg3 cuboctahedra, faces with four equivalent Y(2)Y6Mg6 cuboctahedra, faces with eight equivalent Mg(1)Y9Mg3 cuboctahedra, and faces with eight equivalent Y(1)Y8Mg4 cuboctahedra. In the second Y site, Y(2) is bonded to six equivalent Mg(1) and six equivalent Y(1) atoms to form YY6Mg6 cuboctahedra that share corners with six equivalent Y(2)Y6Mg6 cuboctahedra, corners with twelve equivalent Mg(1)Y9Mg3 cuboctahedra, edges with six equivalent Y(2)Y6Mg6 cuboctahedra, edges with twelve equivalent Y(1)Y8Mg4 cuboctahedra, faces with eight equivalent Mg(1)Y9Mg3 cuboctahedra, and faces with twelve equivalent Y(1)Y8Mg4 cuboctahedra.
MgY2 crystallizes in the trigonal R32 space group. Mg(1) is bonded to three equivalent Mg(1), three equivalent Y(2), and six equivalent Y(1) atoms to form MgY9Mg3 cuboctahedra that share corners with six equivalent Y(2)Y6Mg6 cuboctahedra, corners with twelve equivalent Mg(1)Y9Mg3 cuboctahedra, edges with six equivalent Mg(1)Y9Mg3 cuboctahedra, edges with twelve equivalent Y(1)Y8Mg4 cuboctahedra, faces with four equivalent Mg(1)Y9Mg3 cuboctahedra, faces with four equivalent Y(2)Y6Mg6 cuboctahedra, and faces with twelve equivalent Y(1)Y8Mg4 cuboctahedra. All Mg(1)-Mg(1) bond lengths are 3.46 Å. All Mg(1)-Y(2) bond lengths are 3.46 Å. There are three shorter (3.46 Å) and three longer (3.49 Å) Mg(1)-Y(1) bond lengths. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to four equivalent Mg(1), two equivalent Y(2), and six equivalent Y(1) atoms to form YY8Mg4 cuboctahedra that share corners with eighteen equivalent Y(1)Y8Mg4 cuboctahedra, edges with four equivalent Y(2)Y6Mg6 cuboctahedra, edges with six equivalent Y(1)Y8Mg4 cuboctahedra, edges with eight equivalent Mg(1)Y9Mg3 cuboctahedra, faces with four equivalent Y(2)Y6Mg6 cuboctahedra, faces with eight equivalent Mg(1)Y9Mg3 cuboctahedra, and faces with eight equivalent Y(1)Y8Mg4 cuboctahedra. Both Y(1)-Y(2) bond lengths are 3.49 Å. There are two shorter (3.40 Å) and four longer (3.50 Å) Y(1)-Y(1) bond lengths. In the second Y site, Y(2) is bonded to six equivalent Mg(1) and six equivalent Y(1) atoms to form YY6Mg6 cuboctahedra that share corners with six equivalent Y(2)Y6Mg6 cuboctahedra, corners with twelve equivalent Mg(1)Y9Mg3 cuboctahedra, edges with six equivalent Y(2)Y6Mg6 cuboctahedra, edges with twelve equivalent Y(1)Y8Mg4 cuboctahedra, faces with eight equivalent Mg(1)Y9Mg3 cuboctahedra, and faces with twelve equivalent Y(1)Y8Mg4 cuboctahedra.