Mg6CuAl is beta Cu3Ti-derived structured and crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Cu(1), and two equivalent Al(1) atoms to form distorted MgMg8Al2Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Al2 cuboctahedra, corners with four equivalent Al(1)Mg10Cu2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Mg(2)Mg10Al2 cuboctahedra, edges with two equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Al(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(4)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with four equivalent Cu(1)Mg10Al2 cuboctahedra, faces with two equivalent Mg(2)Mg10Al2 cuboctahedra, faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Al2 cuboctahedra, faces with two equivalent Al(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, and faces with eight equivalent Mg(3)Mg8Al2Cu2 cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Al(1) atoms to form MgMg10Al2 cuboctahedra that share corners with four equivalent Al(1)Mg10Cu2 cuboctahedra, corners with six equivalent Mg(2)Mg10Al2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Al(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(4)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with eight equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Al2 cuboctahedra, faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra, faces with two equivalent Al(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, and faces with six equivalent Cu(1)Mg10Al2 cuboctahedra. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Cu(1), and two equivalent Al(1) atoms to form distorted MgMg8Al2Cu2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Cu2 cuboctahedra, corners with four equivalent Cu(1)Mg10Al2 cuboctahedra, corners with ten equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Mg(4)Mg10Cu2 cuboctahedra, edges with two equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Cu(1)Mg10Al2 cuboctahedra, edges with four equivalent Mg(2)Mg10Al2 cuboctahedra, edges with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with four equivalent Al(1)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Al2 cuboctahedra, faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Al2 cuboctahedra, faces with two equivalent Al(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, and faces with eight equivalent Mg(1)Mg8Al2Cu2 cuboctahedra. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Cu(1) atoms to form distorted MgMg10Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Al2 cuboctahedra, corners with six equivalent Mg(4)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Cu(1)Mg10Al2 cuboctahedra, edges with four equivalent Mg(2)Mg10Al2 cuboctahedra, edges with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Al2 cuboctahedra, faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Al2 cuboctahedra, faces with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, and faces with six equivalent Al(1)Mg10Cu2 cuboctahedra. Cu(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Al(1) atoms to form CuMg10Al2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Cu2 cuboctahedra, corners with six equivalent Cu(1)Mg10Al2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Mg(4)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with four equivalent Al(1)Mg10Cu2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Al2 cuboctahedra, faces with two equivalent Al(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, and faces with six equivalent Mg(2)Mg10Al2 cuboctahedra. Al(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Cu(1) atoms to form AlMg10Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Al2 cuboctahedra, corners with six equivalent Al(1)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Mg(2)Mg10Al2 cuboctahedra, edges with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with four equivalent Cu(1)Mg10Al2 cuboctahedra, edges with eight equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Al2 cuboctahedra, faces with two equivalent Cu(1)Mg10Al2 cuboctahedra, faces with two equivalent Al(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, and faces with six equivalent Mg(4)Mg10Cu2 cuboctahedra.
Mg6CuAl is beta Cu3Ti-derived structured and crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Cu(1), and two equivalent Al(1) atoms to form distorted MgMg8Al2Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Al2 cuboctahedra, corners with four equivalent Al(1)Mg10Cu2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Mg(2)Mg10Al2 cuboctahedra, edges with two equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Al(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(4)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with four equivalent Cu(1)Mg10Al2 cuboctahedra, faces with two equivalent Mg(2)Mg10Al2 cuboctahedra, faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Al2 cuboctahedra, faces with two equivalent Al(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, and faces with eight equivalent Mg(3)Mg8Al2Cu2 cuboctahedra. There is one shorter (2.96 Å) and one longer (3.16 Å) Mg(1)-Mg(1) bond length. There is one shorter (3.04 Å) and one longer (3.07 Å) Mg(1)-Mg(2) bond length. Both Mg(1)-Mg(3) bond lengths are 3.06 Å. Both Mg(1)-Mg(4) bond lengths are 3.03 Å. Both Mg(1)-Cu(1) bond lengths are 2.98 Å. There is one shorter (2.95 Å) and one longer (3.16 Å) Mg(1)-Al(1) bond length. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Al(1) atoms to form MgMg10Al2 cuboctahedra that share corners with four equivalent Al(1)Mg10Cu2 cuboctahedra, corners with six equivalent Mg(2)Mg10Al2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Al(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(4)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with eight equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Al2 cuboctahedra, faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra, faces with two equivalent Al(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, and faces with six equivalent Cu(1)Mg10Al2 cuboctahedra. Both Mg(2)-Mg(4) bond lengths are 3.01 Å. All Mg(2)-Mg(3) bond lengths are 3.02 Å. Both Mg(2)-Al(1) bond lengths are 3.06 Å. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Cu(1), and two equivalent Al(1) atoms to form distorted MgMg8Al2Cu2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Cu2 cuboctahedra, corners with four equivalent Cu(1)Mg10Al2 cuboctahedra, corners with ten equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Mg(4)Mg10Cu2 cuboctahedra, edges with two equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Cu(1)Mg10Al2 cuboctahedra, edges with four equivalent Mg(2)Mg10Al2 cuboctahedra, edges with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with four equivalent Al(1)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Al2 cuboctahedra, faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Al2 cuboctahedra, faces with two equivalent Al(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, and faces with eight equivalent Mg(1)Mg8Al2Cu2 cuboctahedra. There is one shorter (3.02 Å) and one longer (3.10 Å) Mg(3)-Mg(3) bond length. There is one shorter (3.04 Å) and one longer (3.07 Å) Mg(3)-Mg(4) bond length. There is one shorter (3.00 Å) and one longer (3.10 Å) Mg(3)-Cu(1) bond length. Both Mg(3)-Al(1) bond lengths are 3.01 Å. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Cu(1) atoms to form distorted MgMg10Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Al2 cuboctahedra, corners with six equivalent Mg(4)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Cu(1)Mg10Al2 cuboctahedra, edges with four equivalent Mg(2)Mg10Al2 cuboctahedra, edges with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Al2 cuboctahedra, faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Al2 cuboctahedra, faces with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, and faces with six equivalent Al(1)Mg10Cu2 cuboctahedra. Both Mg(4)-Cu(1) bond lengths are 3.06 Å. Cu(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Al(1) atoms to form CuMg10Al2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Cu2 cuboctahedra, corners with six equivalent Cu(1)Mg10Al2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Mg(4)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, edges with four equivalent Al(1)Mg10Cu2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Al2 cuboctahedra, faces with two equivalent Al(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, and faces with six equivalent Mg(2)Mg10Al2 cuboctahedra. Both Cu(1)-Al(1) bond lengths are 2.97 Å. Al(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Cu(1) atoms to form AlMg10Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Al2 cuboctahedra, corners with six equivalent Al(1)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with two equivalent Mg(2)Mg10Al2 cuboctahedra, edges with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, edges with four equivalent Cu(1)Mg10Al2 cuboctahedra, edges with eight equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Al2 cuboctahedra, faces with two equivalent Cu(1)Mg10Al2 cuboctahedra, faces with two equivalent Al(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(1)Mg8Al2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Al2Cu2 cuboctahedra, and faces with six equivalent Mg(4)Mg10Cu2 cuboctahedra.