MgY5 crystallizes in the hexagonal P-62m space group. Mg(1) is bonded to six equivalent Y(1) and six equivalent Y(2) atoms to form MgY12 cuboctahedra that share corners with eighteen equivalent Y(2)Y9Mg3 cuboctahedra, edges with six equivalent Mg(1)Y12 cuboctahedra, edges with twelve equivalent Y(1)Y10Mg2 cuboctahedra, faces with two equivalent Mg(1)Y12 cuboctahedra, faces with six equivalent Y(2)Y9Mg3 cuboctahedra, and faces with twelve equivalent Y(1)Y10Mg2 cuboctahedra. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to two equivalent Mg(1), four equivalent Y(2), and six equivalent Y(1) atoms to form YY10Mg2 cuboctahedra that share corners with eighteen equivalent Y(1)Y10Mg2 cuboctahedra, edges with four equivalent Mg(1)Y12 cuboctahedra, edges with six equivalent Y(1)Y10Mg2 cuboctahedra, edges with eight equivalent Y(2)Y9Mg3 cuboctahedra, faces with four equivalent Mg(1)Y12 cuboctahedra, faces with eight equivalent Y(1)Y10Mg2 cuboctahedra, and faces with eight equivalent Y(2)Y9Mg3 cuboctahedra. In the second Y site, Y(2) is bonded to three equivalent Mg(1), three equivalent Y(2), and six equivalent Y(1) atoms to form YY9Mg3 cuboctahedra that share corners with nine equivalent Mg(1)Y12 cuboctahedra, corners with nine equivalent Y(2)Y9Mg3 cuboctahedra, edges with six equivalent Y(2)Y9Mg3 cuboctahedra, edges with twelve equivalent Y(1)Y10Mg2 cuboctahedra, faces with three equivalent Mg(1)Y12 cuboctahedra, faces with five equivalent Y(2)Y9Mg3 cuboctahedra, and faces with twelve equivalent Y(1)Y10Mg2 cuboctahedra.
MgY5 crystallizes in the hexagonal P-62m space group. Mg(1) is bonded to six equivalent Y(1) and six equivalent Y(2) atoms to form MgY12 cuboctahedra that share corners with eighteen equivalent Y(2)Y9Mg3 cuboctahedra, edges with six equivalent Mg(1)Y12 cuboctahedra, edges with twelve equivalent Y(1)Y10Mg2 cuboctahedra, faces with two equivalent Mg(1)Y12 cuboctahedra, faces with six equivalent Y(2)Y9Mg3 cuboctahedra, and faces with twelve equivalent Y(1)Y10Mg2 cuboctahedra. All Mg(1)-Y(1) bond lengths are 3.44 Å. All Mg(1)-Y(2) bond lengths are 3.58 Å. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to two equivalent Mg(1), four equivalent Y(2), and six equivalent Y(1) atoms to form YY10Mg2 cuboctahedra that share corners with eighteen equivalent Y(1)Y10Mg2 cuboctahedra, edges with four equivalent Mg(1)Y12 cuboctahedra, edges with six equivalent Y(1)Y10Mg2 cuboctahedra, edges with eight equivalent Y(2)Y9Mg3 cuboctahedra, faces with four equivalent Mg(1)Y12 cuboctahedra, faces with eight equivalent Y(1)Y10Mg2 cuboctahedra, and faces with eight equivalent Y(2)Y9Mg3 cuboctahedra. All Y(1)-Y(2) bond lengths are 3.50 Å. There are two shorter (3.48 Å) and four longer (3.64 Å) Y(1)-Y(1) bond lengths. In the second Y site, Y(2) is bonded to three equivalent Mg(1), three equivalent Y(2), and six equivalent Y(1) atoms to form YY9Mg3 cuboctahedra that share corners with nine equivalent Mg(1)Y12 cuboctahedra, corners with nine equivalent Y(2)Y9Mg3 cuboctahedra, edges with six equivalent Y(2)Y9Mg3 cuboctahedra, edges with twelve equivalent Y(1)Y10Mg2 cuboctahedra, faces with three equivalent Mg(1)Y12 cuboctahedra, faces with five equivalent Y(2)Y9Mg3 cuboctahedra, and faces with twelve equivalent Y(1)Y10Mg2 cuboctahedra. All Y(2)-Y(2) bond lengths are 3.58 Å.