Mg6CuSn 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 Sn(1) atoms to form distorted MgMg8Cu2Sn2 cuboctahedra that share corners with four equivalent Mg(3)Mg4Cu2 cuboctahedra, corners with four equivalent Cu(1)Mg10Sn2 cuboctahedra, corners with four equivalent Sn(1)Mg10Cu2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with two equivalent Mg(3)Mg4Cu2 cuboctahedra, edges with two equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with two equivalent Cu(1)Mg10Sn2 cuboctahedra, edges with two equivalent Sn(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Sn2 cuboctahedra, faces with two equivalent Sn(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Sn2 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 Sn(1) atoms. In the third Mg site, Mg(3) is bonded to four equivalent Mg(1) and two equivalent Cu(1) atoms to form distorted MgMg4Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Sn2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with two equivalent Cu(1)Mg10Sn2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with six equivalent Sn(1)Mg10Cu2 cuboctahedra, and faces with two equivalent Mg(3)Mg4Cu2 cuboctahedra. In the fourth Mg site, Mg(4) is bonded in a distorted water-like geometry to four equivalent Mg(1) and two equivalent Sn(1) atoms. Cu(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Sn(1) atoms to form CuMg10Sn2 cuboctahedra that share corners with four equivalent Mg(3)Mg4Cu2 cuboctahedra, corners with four equivalent Sn(1)Mg10Cu2 cuboctahedra, corners with six equivalent Cu(1)Mg10Sn2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with two equivalent Mg(3)Mg4Cu2 cuboctahedra, edges with two equivalent Sn(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, faces with two equivalent Cu(1)Mg10Sn2 cuboctahedra, faces with two equivalent Sn(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra. Sn(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Cu(1) atoms to form SnMg10Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Sn2 cuboctahedra, corners with six equivalent Sn(1)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with two equivalent Cu(1)Mg10Sn2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with six equivalent Mg(3)Mg4Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Sn2 cuboctahedra, faces with two equivalent Sn(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra.
Mg6CuSn 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 Sn(1) atoms to form distorted MgMg8Cu2Sn2 cuboctahedra that share corners with four equivalent Mg(3)Mg4Cu2 cuboctahedra, corners with four equivalent Cu(1)Mg10Sn2 cuboctahedra, corners with four equivalent Sn(1)Mg10Cu2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with two equivalent Mg(3)Mg4Cu2 cuboctahedra, edges with two equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with two equivalent Cu(1)Mg10Sn2 cuboctahedra, edges with two equivalent Sn(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Sn2 cuboctahedra, faces with two equivalent Sn(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra. There is one shorter (3.16 Å) and one longer (3.18 Å) Mg(1)-Mg(1) bond length. Both Mg(1)-Mg(2) bond lengths are 3.07 Å. Both Mg(1)-Mg(3) bond lengths are 3.08 Å. Both Mg(1)-Mg(4) bond lengths are 3.06 Å. There is one shorter (3.11 Å) and one longer (3.13 Å) Mg(1)-Cu(1) bond length. There is one shorter (3.12 Å) and one longer (3.13 Å) Mg(1)-Sn(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 Sn(1) atoms. Both Mg(2)-Cu(1) bond lengths are 3.03 Å. Both Mg(2)-Sn(1) bond lengths are 3.10 Å. In the third Mg site, Mg(3) is bonded to four equivalent Mg(1) and two equivalent Cu(1) atoms to form distorted MgMg4Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Sn2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with two equivalent Cu(1)Mg10Sn2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with six equivalent Sn(1)Mg10Cu2 cuboctahedra, and faces with two equivalent Mg(3)Mg4Cu2 cuboctahedra. Both Mg(3)-Cu(1) bond lengths are 3.02 Å. In the fourth Mg site, Mg(4) is bonded in a distorted water-like geometry to four equivalent Mg(1) and two equivalent Sn(1) atoms. Both Mg(4)-Sn(1) bond lengths are 3.06 Å. Cu(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Sn(1) atoms to form CuMg10Sn2 cuboctahedra that share corners with four equivalent Mg(3)Mg4Cu2 cuboctahedra, corners with four equivalent Sn(1)Mg10Cu2 cuboctahedra, corners with six equivalent Cu(1)Mg10Sn2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with two equivalent Mg(3)Mg4Cu2 cuboctahedra, edges with two equivalent Sn(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, faces with two equivalent Cu(1)Mg10Sn2 cuboctahedra, faces with two equivalent Sn(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra. Both Cu(1)-Sn(1) bond lengths are 3.17 Å. Sn(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Cu(1) atoms to form SnMg10Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Sn2 cuboctahedra, corners with six equivalent Sn(1)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with two equivalent Cu(1)Mg10Sn2 cuboctahedra, edges with four equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra, edges with six equivalent Mg(3)Mg4Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Sn2 cuboctahedra, faces with two equivalent Sn(1)Mg10Cu2 cuboctahedra, and faces with four equivalent Mg(1)Mg8Cu2Sn2 cuboctahedra.