Mg2Y crystallizes in the hexagonal P-62m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), six equivalent Mg(1), and four equivalent Y(1) atoms to form distorted MgY4Mg8 cuboctahedra that share corners with eighteen equivalent Mg(1)Y4Mg8 cuboctahedra, edges with four equivalent Mg(2)Y6Mg6 cuboctahedra, edges with six equivalent Mg(1)Y4Mg8 cuboctahedra, edges with eight equivalent Y(1)Y3Mg9 cuboctahedra, faces with four equivalent Mg(2)Y6Mg6 cuboctahedra, faces with eight equivalent Mg(1)Y4Mg8 cuboctahedra, and faces with eight equivalent Y(1)Y3Mg9 cuboctahedra. In the second Mg site, Mg(2) is bonded to six equivalent Mg(1) and six equivalent Y(1) atoms to form MgY6Mg6 cuboctahedra that share corners with eighteen equivalent Y(1)Y3Mg9 cuboctahedra, edges with six equivalent Mg(2)Y6Mg6 cuboctahedra, edges with twelve equivalent Mg(1)Y4Mg8 cuboctahedra, faces with two equivalent Mg(2)Y6Mg6 cuboctahedra, faces with six equivalent Y(1)Y3Mg9 cuboctahedra, and faces with twelve equivalent Mg(1)Y4Mg8 cuboctahedra. Y(1) is bonded to three equivalent Mg(2), six equivalent Mg(1), and three equivalent Y(1) atoms to form YY3Mg9 cuboctahedra that share corners with nine equivalent Mg(2)Y6Mg6 cuboctahedra, corners with nine equivalent Y(1)Y3Mg9 cuboctahedra, edges with six equivalent Y(1)Y3Mg9 cuboctahedra, edges with twelve equivalent Mg(1)Y4Mg8 cuboctahedra, faces with three equivalent Mg(2)Y6Mg6 cuboctahedra, faces with five equivalent Y(1)Y3Mg9 cuboctahedra, and faces with twelve equivalent Mg(1)Y4Mg8 cuboctahedra.
Mg2Y crystallizes in the hexagonal P-62m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(2), six equivalent Mg(1), and four equivalent Y(1) atoms to form distorted MgY4Mg8 cuboctahedra that share corners with eighteen equivalent Mg(1)Y4Mg8 cuboctahedra, edges with four equivalent Mg(2)Y6Mg6 cuboctahedra, edges with six equivalent Mg(1)Y4Mg8 cuboctahedra, edges with eight equivalent Y(1)Y3Mg9 cuboctahedra, faces with four equivalent Mg(2)Y6Mg6 cuboctahedra, faces with eight equivalent Mg(1)Y4Mg8 cuboctahedra, and faces with eight equivalent Y(1)Y3Mg9 cuboctahedra. Both Mg(1)-Mg(2) bond lengths are 3.22 Å. There are two shorter (3.27 Å) and four longer (3.49 Å) Mg(1)-Mg(1) bond lengths. All Mg(1)-Y(1) bond lengths are 3.30 Å. In the second Mg site, Mg(2) is bonded to six equivalent Mg(1) and six equivalent Y(1) atoms to form MgY6Mg6 cuboctahedra that share corners with eighteen equivalent Y(1)Y3Mg9 cuboctahedra, edges with six equivalent Mg(2)Y6Mg6 cuboctahedra, edges with twelve equivalent Mg(1)Y4Mg8 cuboctahedra, faces with two equivalent Mg(2)Y6Mg6 cuboctahedra, faces with six equivalent Y(1)Y3Mg9 cuboctahedra, and faces with twelve equivalent Mg(1)Y4Mg8 cuboctahedra. All Mg(2)-Y(1) bond lengths are 3.42 Å. Y(1) is bonded to three equivalent Mg(2), six equivalent Mg(1), and three equivalent Y(1) atoms to form YY3Mg9 cuboctahedra that share corners with nine equivalent Mg(2)Y6Mg6 cuboctahedra, corners with nine equivalent Y(1)Y3Mg9 cuboctahedra, edges with six equivalent Y(1)Y3Mg9 cuboctahedra, edges with twelve equivalent Mg(1)Y4Mg8 cuboctahedra, faces with three equivalent Mg(2)Y6Mg6 cuboctahedra, faces with five equivalent Y(1)Y3Mg9 cuboctahedra, and faces with twelve equivalent Mg(1)Y4Mg8 cuboctahedra. All Y(1)-Y(1) bond lengths are 3.42 Å.