MgY2 crystallizes in the orthorhombic Cmcm space group. Mg(1) is bonded in a 10-coordinate geometry to four equivalent Mg(1), two equivalent Y(2), and four equivalent Y(1) atoms. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to four equivalent Mg(1), two equivalent Y(1), and six equivalent Y(2) atoms to form distorted YY8Mg4 cuboctahedra that share corners with six equivalent Y(2)Y10Mg2 cuboctahedra, corners with six equivalent Y(1)Y8Mg4 cuboctahedra, edges with seven equivalent Y(2)Y10Mg2 cuboctahedra, edges with eight equivalent Y(1)Y8Mg4 cuboctahedra, faces with six equivalent Y(2)Y10Mg2 cuboctahedra, and faces with six equivalent Y(1)Y8Mg4 cuboctahedra. In the second Y site, Y(2) is bonded to two equivalent Mg(1), four equivalent Y(2), and six equivalent Y(1) atoms to form distorted YY10Mg2 cuboctahedra that share corners with six equivalent Y(2)Y10Mg2 cuboctahedra, corners with six equivalent Y(1)Y8Mg4 cuboctahedra, edges with seven equivalent Y(1)Y8Mg4 cuboctahedra, faces with six equivalent Y(1)Y8Mg4 cuboctahedra, and faces with ten equivalent Y(2)Y10Mg2 cuboctahedra.
MgY2 crystallizes in the orthorhombic Cmcm space group. Mg(1) is bonded in a 10-coordinate geometry to four equivalent Mg(1), two equivalent Y(2), and four equivalent Y(1) atoms. All Mg(1)-Mg(1) bond lengths are 3.48 Å. Both Mg(1)-Y(2) bond lengths are 3.39 Å. There are two shorter (3.36 Å) and two longer (3.38 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(1), and six equivalent Y(2) atoms to form distorted YY8Mg4 cuboctahedra that share corners with six equivalent Y(2)Y10Mg2 cuboctahedra, corners with six equivalent Y(1)Y8Mg4 cuboctahedra, edges with seven equivalent Y(2)Y10Mg2 cuboctahedra, edges with eight equivalent Y(1)Y8Mg4 cuboctahedra, faces with six equivalent Y(2)Y10Mg2 cuboctahedra, and faces with six equivalent Y(1)Y8Mg4 cuboctahedra. Both Y(1)-Y(1) bond lengths are 3.72 Å. There are four shorter (3.49 Å) and two longer (3.58 Å) Y(1)-Y(2) bond lengths. In the second Y site, Y(2) is bonded to two equivalent Mg(1), four equivalent Y(2), and six equivalent Y(1) atoms to form distorted YY10Mg2 cuboctahedra that share corners with six equivalent Y(2)Y10Mg2 cuboctahedra, corners with six equivalent Y(1)Y8Mg4 cuboctahedra, edges with seven equivalent Y(1)Y8Mg4 cuboctahedra, faces with six equivalent Y(1)Y8Mg4 cuboctahedra, and faces with ten equivalent Y(2)Y10Mg2 cuboctahedra. There are two shorter (3.49 Å) and two longer (3.72 Å) Y(2)-Y(2) bond lengths.