MgY2 crystallizes in the hexagonal P-62m space group. Mg(1) is bonded to three equivalent Mg(1), three equivalent Y(2), and six equivalent Y(1) atoms to form distorted MgY9Mg3 cuboctahedra that share corners with nine equivalent Mg(1)Y9Mg3 cuboctahedra, corners with nine equivalent Y(2)Y6Mg6 cuboctahedra, edges with six equivalent Mg(1)Y9Mg3 cuboctahedra, edges with twelve equivalent Y(1)Y8Mg4 cuboctahedra, faces with three equivalent Y(2)Y6Mg6 cuboctahedra, faces with five equivalent Mg(1)Y9Mg3 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 eighteen equivalent Mg(1)Y9Mg3 cuboctahedra, edges with six equivalent Y(2)Y6Mg6 cuboctahedra, edges with twelve equivalent Y(1)Y8Mg4 cuboctahedra, faces with two equivalent Y(2)Y6Mg6 cuboctahedra, faces with six equivalent Mg(1)Y9Mg3 cuboctahedra, and faces with twelve equivalent Y(1)Y8Mg4 cuboctahedra.
MgY2 crystallizes in the hexagonal P-62m space group. Mg(1) is bonded to three equivalent Mg(1), three equivalent Y(2), and six equivalent Y(1) atoms to form distorted MgY9Mg3 cuboctahedra that share corners with nine equivalent Mg(1)Y9Mg3 cuboctahedra, corners with nine equivalent Y(2)Y6Mg6 cuboctahedra, edges with six equivalent Mg(1)Y9Mg3 cuboctahedra, edges with twelve equivalent Y(1)Y8Mg4 cuboctahedra, faces with three equivalent Y(2)Y6Mg6 cuboctahedra, faces with five equivalent Mg(1)Y9Mg3 cuboctahedra, and faces with twelve equivalent Y(1)Y8Mg4 cuboctahedra. All Mg(1)-Mg(1) bond lengths are 3.49 Å. All Mg(1)-Y(2) bond lengths are 3.49 Å. All Mg(1)-Y(1) bond lengths are 3.45 Å. 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 3.50 Å. There are four shorter (3.44 Å) and two longer (3.60 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 eighteen equivalent Mg(1)Y9Mg3 cuboctahedra, edges with six equivalent Y(2)Y6Mg6 cuboctahedra, edges with twelve equivalent Y(1)Y8Mg4 cuboctahedra, faces with two equivalent Y(2)Y6Mg6 cuboctahedra, faces with six equivalent Mg(1)Y9Mg3 cuboctahedra, and faces with twelve equivalent Y(1)Y8Mg4 cuboctahedra.