Mg7Y crystallizes in the hexagonal P-6m2 space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(3); four Mg(1,1); four equivalent Mg(2); and two equivalent Y(1) atoms to form MgY2Mg10 cuboctahedra that share corners with four equivalent Y(1)Mg12 cuboctahedra; corners with fourteen Mg(1,1,1)Y2Mg10 cuboctahedra; edges with two equivalent Y(1)Mg12 cuboctahedra; edges with four equivalent Mg(3)Mg12 cuboctahedra; edges with four Mg(1,1)Y2Mg10 cuboctahedra; edges with eight equivalent Mg(2)Y2Mg10 cuboctahedra; faces with two equivalent Mg(3)Mg12 cuboctahedra; faces with two equivalent Y(1)Mg12 cuboctahedra; faces with six Mg(1,1,1)Y2Mg10 cuboctahedra; and faces with ten equivalent Mg(2)Y2Mg10 cuboctahedra. In the second Mg site, Mg(1) is bonded to two equivalent Mg(3); four Mg(1,1); four equivalent Mg(2); and two equivalent Y(1) atoms to form MgY2Mg10 cuboctahedra that share corners with four equivalent Y(1)Mg12 cuboctahedra; corners with fourteen Mg(1,1,1)Y2Mg10 cuboctahedra; edges with two equivalent Y(1)Mg12 cuboctahedra; edges with four equivalent Mg(3)Mg12 cuboctahedra; edges with four Mg(1,1)Y2Mg10 cuboctahedra; edges with eight equivalent Mg(2)Y2Mg10 cuboctahedra; faces with two equivalent Mg(3)Mg12 cuboctahedra; faces with two equivalent Y(1)Mg12 cuboctahedra; faces with six Mg(1,1,1)Y2Mg10 cuboctahedra; and faces with ten equivalent Mg(2)Y2Mg10 cuboctahedra. In the third Mg site, Mg(1) is bonded to two equivalent Mg(3); four Mg(1,1); four equivalent Mg(2); and two equivalent Y(1) atoms to form MgY2Mg10 cuboctahedra that share corners with four equivalent Y(1)Mg12 cuboctahedra; corners with fourteen Mg(1,1,1)Y2Mg10 cuboctahedra; edges with two equivalent Y(1)Mg12 cuboctahedra; edges with four equivalent Mg(3)Mg12 cuboctahedra; edges with four Mg(1,1)Y2Mg10 cuboctahedra; edges with eight equivalent Mg(2)Y2Mg10 cuboctahedra; faces with two equivalent Mg(3)Mg12 cuboctahedra; faces with two equivalent Y(1)Mg12 cuboctahedra; faces with six Mg(1,1,1)Y2Mg10 cuboctahedra; and faces with ten equivalent Mg(2)Y2Mg10 cuboctahedra. In the fourth Mg site, Mg(2) is bonded to two equivalent Mg(3); four Mg(1,1); four equivalent Mg(2); and two equivalent Y(1) atoms to form MgY2Mg10 cuboctahedra that share corners with four equivalent Mg(3)Mg12 cuboctahedra; corners with fourteen equivalent Mg(2)Y2Mg10 cuboctahedra; edges with two equivalent Mg(3)Mg12 cuboctahedra; edges with four equivalent Mg(2)Y2Mg10 cuboctahedra; edges with four equivalent Y(1)Mg12 cuboctahedra; edges with eight Mg(1,1)Y2Mg10 cuboctahedra; faces with two equivalent Mg(3)Mg12 cuboctahedra; faces with two equivalent Y(1)Mg12 cuboctahedra; faces with six equivalent Mg(2)Y2Mg10 cuboctahedra; and faces with ten Mg(1,1,1)Y2Mg10 cuboctahedra. In the fifth Mg site, Mg(3) is bonded to six Mg(1,1,1) and six equivalent Mg(2) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(3)Mg12 cuboctahedra; corners with twelve equivalent Mg(2)Y2Mg10 cuboctahedra; edges with six equivalent Mg(2)Y2Mg10 cuboctahedra; edges with twelve Mg(1,1,1)Y2Mg10 cuboctahedra; faces with two equivalent Mg(3)Mg12 cuboctahedra; faces with six Mg(1,1,1)Y2Mg10 cuboctahedra; faces with six equivalent Mg(2)Y2Mg10 cuboctahedra; and faces with six equivalent Y(1)Mg12 cuboctahedra. Y(1) is bonded to six Mg(1,1,1) and six equivalent Mg(2) atoms to form YMg12 cuboctahedra that share corners with six equivalent Y(1)Mg12 cuboctahedra; corners with twelve Mg(1,1,1)Y2Mg10 cuboctahedra; edges with six Mg(1,1,1)Y2Mg10 cuboctahedra; edges with twelve equivalent Mg(2)Y2Mg10 cuboctahedra; faces with two equivalent Y(1)Mg12 cuboctahedra; faces with six equivalent Mg(3)Mg12 cuboctahedra; faces with six Mg(1,1,1)Y2Mg10 cuboctahedra; and faces with six equivalent Mg(2)Y2Mg10 cuboctahedra.
Mg7Y crystallizes in the hexagonal P-6m2 space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(3); four Mg(1,1); four equivalent Mg(2); and two equivalent Y(1) atoms to form MgY2Mg10 cuboctahedra that share corners with four equivalent Y(1)Mg12 cuboctahedra; corners with fourteen Mg(1,1,1)Y2Mg10 cuboctahedra; edges with two equivalent Y(1)Mg12 cuboctahedra; edges with four equivalent Mg(3)Mg12 cuboctahedra; edges with four Mg(1,1)Y2Mg10 cuboctahedra; edges with eight equivalent Mg(2)Y2Mg10 cuboctahedra; faces with two equivalent Mg(3)Mg12 cuboctahedra; faces with two equivalent Y(1)Mg12 cuboctahedra; faces with six Mg(1,1,1)Y2Mg10 cuboctahedra; and faces with ten equivalent Mg(2)Y2Mg10 cuboctahedra. Both Mg(1)-Mg(3) bond lengths are 3.23 Å. There are two shorter (3.21 Å) and two longer (3.38 Å) Mg(1)-Mg(1,1) bond lengths. All Mg(1)-Mg(2) bond lengths are 3.18 Å. Both Mg(1)-Y(1) bond lengths are 3.29 Å. In the second Mg site, Mg(1) is bonded to two equivalent Mg(3); four Mg(1,1); four equivalent Mg(2); and two equivalent Y(1) atoms to form MgY2Mg10 cuboctahedra that share corners with four equivalent Y(1)Mg12 cuboctahedra; corners with fourteen Mg(1,1,1)Y2Mg10 cuboctahedra; edges with two equivalent Y(1)Mg12 cuboctahedra; edges with four equivalent Mg(3)Mg12 cuboctahedra; edges with four Mg(1,1)Y2Mg10 cuboctahedra; edges with eight equivalent Mg(2)Y2Mg10 cuboctahedra; faces with two equivalent Mg(3)Mg12 cuboctahedra; faces with two equivalent Y(1)Mg12 cuboctahedra; faces with six Mg(1,1,1)Y2Mg10 cuboctahedra; and faces with ten equivalent Mg(2)Y2Mg10 cuboctahedra. Both Mg(1)-Mg(3) bond lengths are 3.23 Å. There is one shorter (3.21 Å) and one longer (3.38 Å) Mg(1)-Mg(1) bond length. All Mg(1)-Mg(2) bond lengths are 3.18 Å. Both Mg(1)-Y(1) bond lengths are 3.29 Å. In the third Mg site, Mg(1) is bonded to two equivalent Mg(3); four Mg(1,1); four equivalent Mg(2); and two equivalent Y(1) atoms to form MgY2Mg10 cuboctahedra that share corners with four equivalent Y(1)Mg12 cuboctahedra; corners with fourteen Mg(1,1,1)Y2Mg10 cuboctahedra; edges with two equivalent Y(1)Mg12 cuboctahedra; edges with four equivalent Mg(3)Mg12 cuboctahedra; edges with four Mg(1,1)Y2Mg10 cuboctahedra; edges with eight equivalent Mg(2)Y2Mg10 cuboctahedra; faces with two equivalent Mg(3)Mg12 cuboctahedra; faces with two equivalent Y(1)Mg12 cuboctahedra; faces with six Mg(1,1,1)Y2Mg10 cuboctahedra; and faces with ten equivalent Mg(2)Y2Mg10 cuboctahedra. Both Mg(1)-Mg(3) bond lengths are 3.23 Å. All Mg(1)-Mg(2) bond lengths are 3.18 Å. Both Mg(1)-Y(1) bond lengths are 3.29 Å. In the fourth Mg site, Mg(2) is bonded to two equivalent Mg(3); four Mg(1,1); four equivalent Mg(2); and two equivalent Y(1) atoms to form MgY2Mg10 cuboctahedra that share corners with four equivalent Mg(3)Mg12 cuboctahedra; corners with fourteen equivalent Mg(2)Y2Mg10 cuboctahedra; edges with two equivalent Mg(3)Mg12 cuboctahedra; edges with four equivalent Mg(2)Y2Mg10 cuboctahedra; edges with four equivalent Y(1)Mg12 cuboctahedra; edges with eight Mg(1,1)Y2Mg10 cuboctahedra; faces with two equivalent Mg(3)Mg12 cuboctahedra; faces with two equivalent Y(1)Mg12 cuboctahedra; faces with six equivalent Mg(2)Y2Mg10 cuboctahedra; and faces with ten Mg(1,1,1)Y2Mg10 cuboctahedra. Both Mg(2)-Mg(3) bond lengths are 3.29 Å. There are two shorter (3.23 Å) and two longer (3.35 Å) Mg(2)-Mg(2) bond lengths. Both Mg(2)-Y(1) bond lengths are 3.22 Å. In the fifth Mg site, Mg(3) is bonded to six Mg(1,1,1) and six equivalent Mg(2) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(3)Mg12 cuboctahedra; corners with twelve equivalent Mg(2)Y2Mg10 cuboctahedra; edges with six equivalent Mg(2)Y2Mg10 cuboctahedra; edges with twelve Mg(1,1,1)Y2Mg10 cuboctahedra; faces with two equivalent Mg(3)Mg12 cuboctahedra; faces with six Mg(1,1,1)Y2Mg10 cuboctahedra; faces with six equivalent Mg(2)Y2Mg10 cuboctahedra; and faces with six equivalent Y(1)Mg12 cuboctahedra. Y(1) is bonded to six Mg(1,1,1) and six equivalent Mg(2) atoms to form YMg12 cuboctahedra that share corners with six equivalent Y(1)Mg12 cuboctahedra; corners with twelve Mg(1,1,1)Y2Mg10 cuboctahedra; edges with six Mg(1,1,1)Y2Mg10 cuboctahedra; edges with twelve equivalent Mg(2)Y2Mg10 cuboctahedra; faces with two equivalent Y(1)Mg12 cuboctahedra; faces with six equivalent Mg(3)Mg12 cuboctahedra; faces with six Mg(1,1,1)Y2Mg10 cuboctahedra; and faces with six equivalent Mg(2)Y2Mg10 cuboctahedra.