Mg6CuBi 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 Bi(1) atoms to form distorted MgMg8Cu2Bi2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Bi2 cuboctahedra, corners with four equivalent Bi(1)Mg10Cu2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, edges with two equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, edges with two equivalent Cu(1)Mg10Bi2 cuboctahedra, edges with two equivalent Bi(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Bi2 cuboctahedra, faces with two equivalent Bi(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent Mg(1), two equivalent Cu(1), and two equivalent Bi(1) atoms. In the third Mg site, Mg(3) is bonded in a distorted water-like geometry to four equivalent Mg(1) and two equivalent Cu(1) atoms. In the fourth Mg site, Mg(4) is bonded in a distorted water-like geometry to four equivalent Mg(1) and two equivalent Bi(1) atoms. Cu(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Bi(1) atoms to form CuMg10Bi2 cuboctahedra that share corners with four equivalent Bi(1)Mg10Cu2 cuboctahedra, corners with six equivalent Cu(1)Mg10Bi2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, edges with two equivalent Bi(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, faces with two equivalent Cu(1)Mg10Bi2 cuboctahedra, faces with two equivalent Bi(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra. Bi(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Cu(1) atoms to form BiMg10Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Bi2 cuboctahedra, corners with six equivalent Bi(1)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, edges with two equivalent Cu(1)Mg10Bi2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, faces with two equivalent Cu(1)Mg10Bi2 cuboctahedra, faces with two equivalent Bi(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra.
Mg6CuBi 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 Bi(1) atoms to form distorted MgMg8Cu2Bi2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Bi2 cuboctahedra, corners with four equivalent Bi(1)Mg10Cu2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, edges with two equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, edges with two equivalent Cu(1)Mg10Bi2 cuboctahedra, edges with two equivalent Bi(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Bi2 cuboctahedra, faces with two equivalent Bi(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra. There is one shorter (3.22 Å) and one longer (3.27 Å) Mg(1)-Mg(1) bond length. Both Mg(1)-Mg(2) bond lengths are 3.11 Å. Both Mg(1)-Mg(3) bond lengths are 3.12 Å. Both Mg(1)-Mg(4) bond lengths are 3.09 Å. There is one shorter (3.17 Å) and one longer (3.18 Å) Mg(1)-Cu(1) bond length. There is one shorter (3.17 Å) and one longer (3.18 Å) Mg(1)-Bi(1) bond length. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent Mg(1), two equivalent Cu(1), and two equivalent Bi(1) atoms. Both Mg(2)-Cu(1) bond lengths are 3.03 Å. Both Mg(2)-Bi(1) bond lengths are 3.18 Å. In the third Mg site, Mg(3) is bonded in a distorted water-like geometry to four equivalent Mg(1) and two equivalent Cu(1) atoms. Both Mg(3)-Cu(1) bond lengths are 3.07 Å. In the fourth Mg site, Mg(4) is bonded in a distorted water-like geometry to four equivalent Mg(1) and two equivalent Bi(1) atoms. Both Mg(4)-Bi(1) bond lengths are 3.14 Å. Cu(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Bi(1) atoms to form CuMg10Bi2 cuboctahedra that share corners with four equivalent Bi(1)Mg10Cu2 cuboctahedra, corners with six equivalent Cu(1)Mg10Bi2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, edges with two equivalent Bi(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, faces with two equivalent Cu(1)Mg10Bi2 cuboctahedra, faces with two equivalent Bi(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra. Both Cu(1)-Bi(1) bond lengths are 3.25 Å. Bi(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Cu(1) atoms to form BiMg10Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Bi2 cuboctahedra, corners with six equivalent Bi(1)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, edges with two equivalent Cu(1)Mg10Bi2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra, faces with two equivalent Cu(1)Mg10Bi2 cuboctahedra, faces with two equivalent Bi(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Bi2 cuboctahedra.