Mg6FeCu crystallizes in the orthorhombic Amm2 space group. There are seven 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 Fe(1), and two equivalent Cu(1) atoms to form distorted MgMg8Fe2Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Fe2 cuboctahedra; corners with four equivalent Fe(1)Mg10Cu2 cuboctahedra; corners with ten Mg(1,1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Mg(2)Mg10Fe2 cuboctahedra; edges with two equivalent Mg(1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Fe(1)Mg10Cu2 cuboctahedra; edges with four equivalent Mg(4)Mg10Cu2 cuboctahedra; edges with four equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra; faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Cu2 cuboctahedra; faces with two equivalent Cu(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra. In the second 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 Fe(1), and two equivalent Cu(1) atoms to form distorted MgMg8Fe2Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Fe2 cuboctahedra; corners with four equivalent Fe(1)Mg10Cu2 cuboctahedra; corners with ten Mg(1,1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Mg(2)Mg10Fe2 cuboctahedra; edges with two equivalent Mg(1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Fe(1)Mg10Cu2 cuboctahedra; edges with four equivalent Mg(4)Mg10Cu2 cuboctahedra; edges with four equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra; faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Cu2 cuboctahedra; faces with two equivalent Cu(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra. In the third Mg site, Mg(2) is bonded to two equivalent Mg(4); four Mg(1,1); four Mg(3,3); and two equivalent Fe(1) atoms to form distorted MgMg10Fe2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Cu2 cuboctahedra; corners with six equivalent Mg(2)Mg10Fe2 cuboctahedra; corners with eight Mg(1,1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Fe(1)Mg10Cu2 cuboctahedra; edges with four equivalent Mg(4)Mg10Cu2 cuboctahedra; edges with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra; faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Cu2 cuboctahedra; faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; and faces with six equivalent Cu(1)Mg10Fe2 cuboctahedra. In the fourth Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Fe(1), and two equivalent Cu(1) atoms. In the fifth Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Fe(1), and two equivalent Cu(1) atoms. In the sixth Mg site, Mg(4) is bonded to two equivalent Mg(2); four Mg(1,1); four Mg(3,3,3); and two equivalent Cu(1) atoms to form distorted MgMg10Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Fe2 cuboctahedra; corners with six equivalent Mg(4)Mg10Cu2 cuboctahedra; edges with two equivalent Cu(1)Mg10Fe2 cuboctahedra; edges with four equivalent Mg(2)Mg10Fe2 cuboctahedra; edges with eight Mg(1,1)Mg8Fe2Cu2 cuboctahedra; faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra; faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra; faces with two equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; and faces with six equivalent Fe(1)Mg10Cu2 cuboctahedra. In the seventh Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Fe(1), and two equivalent Cu(1) atoms. Fe(1) is bonded to two equivalent Mg(2); four Mg(1,1); four Mg(3,3); and two equivalent Cu(1) atoms to form FeMg10Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Fe2 cuboctahedra; corners with six equivalent Fe(1)Mg10Cu2 cuboctahedra; corners with eight Mg(1,1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Mg(2)Mg10Fe2 cuboctahedra; edges with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; edges with four equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Cu2 cuboctahedra; faces with two equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; and faces with six equivalent Mg(4)Mg10Cu2 cuboctahedra. Cu(1) is bonded to two equivalent Mg(4); four Mg(1,1); four Mg(3,3,3); and two equivalent Fe(1) atoms to form CuMg10Fe2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Cu2 cuboctahedra; corners with six equivalent Cu(1)Mg10Fe2 cuboctahedra; edges with two equivalent Mg(4)Mg10Cu2 cuboctahedra; edges with four equivalent Fe(1)Mg10Cu2 cuboctahedra; edges with eight Mg(1,1)Mg8Fe2Cu2 cuboctahedra; faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra; faces with two equivalent Fe(1)Mg10Cu2 cuboctahedra; faces with two equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; and faces with six equivalent Mg(2)Mg10Fe2 cuboctahedra.
Mg6FeCu crystallizes in the orthorhombic Amm2 space group. There are seven 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 Fe(1), and two equivalent Cu(1) atoms to form distorted MgMg8Fe2Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Fe2 cuboctahedra; corners with four equivalent Fe(1)Mg10Cu2 cuboctahedra; corners with ten Mg(1,1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Mg(2)Mg10Fe2 cuboctahedra; edges with two equivalent Mg(1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Fe(1)Mg10Cu2 cuboctahedra; edges with four equivalent Mg(4)Mg10Cu2 cuboctahedra; edges with four equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra; faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Cu2 cuboctahedra; faces with two equivalent Cu(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra. There is one shorter (2.88 Å) and one longer (3.14 Å) Mg(1)-Mg(1) bond length. There is one shorter (2.99 Å) and one longer (3.01 Å) Mg(1)-Mg(2) bond length. Both Mg(1)-Mg(3) bond lengths are 3.05 Å. Both Mg(1)-Mg(4) bond lengths are 2.97 Å. There is one shorter (2.88 Å) and one longer (3.12 Å) Mg(1)-Fe(1) bond length. Both Mg(1)-Cu(1) bond lengths are 2.94 Å. In the second 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 Fe(1), and two equivalent Cu(1) atoms to form distorted MgMg8Fe2Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Fe2 cuboctahedra; corners with four equivalent Fe(1)Mg10Cu2 cuboctahedra; corners with ten Mg(1,1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Mg(2)Mg10Fe2 cuboctahedra; edges with two equivalent Mg(1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Fe(1)Mg10Cu2 cuboctahedra; edges with four equivalent Mg(4)Mg10Cu2 cuboctahedra; edges with four equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra; faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Cu2 cuboctahedra; faces with two equivalent Cu(1)Mg10Fe2 cuboctahedra; and faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra. There is one shorter (2.99 Å) and one longer (3.01 Å) Mg(1)-Mg(2) bond length. Both Mg(1)-Mg(3) bond lengths are 3.05 Å. Both Mg(1)-Mg(4) bond lengths are 2.97 Å. There is one shorter (2.88 Å) and one longer (3.12 Å) Mg(1)-Fe(1) bond length. Both Mg(1)-Cu(1) bond lengths are 2.94 Å. In the third Mg site, Mg(2) is bonded to two equivalent Mg(4); four Mg(1,1); four Mg(3,3); and two equivalent Fe(1) atoms to form distorted MgMg10Fe2 cuboctahedra that share corners with four equivalent Fe(1)Mg10Cu2 cuboctahedra; corners with six equivalent Mg(2)Mg10Fe2 cuboctahedra; corners with eight Mg(1,1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Fe(1)Mg10Cu2 cuboctahedra; edges with four equivalent Mg(4)Mg10Cu2 cuboctahedra; edges with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra; faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Cu2 cuboctahedra; faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; and faces with six equivalent Cu(1)Mg10Fe2 cuboctahedra. Both Mg(2)-Mg(4) bond lengths are 2.97 Å. All Mg(2)-Mg(3,3) bond lengths are 2.97 Å. Both Mg(2)-Fe(1) bond lengths are 3.01 Å. In the fourth Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Fe(1), and two equivalent Cu(1) atoms. There is one shorter (2.86 Å) and one longer (3.16 Å) Mg(3)-Mg(3) bond length. There is one shorter (2.98 Å) and one longer (3.03 Å) Mg(3)-Mg(4) bond length. Both Mg(3)-Fe(1) bond lengths are 2.91 Å. There is one shorter (2.81 Å) and one longer (3.19 Å) Mg(3)-Cu(1) bond length. In the fifth Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Fe(1), and two equivalent Cu(1) atoms. There is one shorter (2.98 Å) and one longer (3.03 Å) Mg(3)-Mg(4) bond length. Both Mg(3)-Fe(1) bond lengths are 2.91 Å. There is one shorter (2.81 Å) and one longer (3.19 Å) Mg(3)-Cu(1) bond length. In the sixth Mg site, Mg(4) is bonded to two equivalent Mg(2); four Mg(1,1); four Mg(3,3,3); and two equivalent Cu(1) atoms to form distorted MgMg10Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Fe2 cuboctahedra; corners with six equivalent Mg(4)Mg10Cu2 cuboctahedra; edges with two equivalent Cu(1)Mg10Fe2 cuboctahedra; edges with four equivalent Mg(2)Mg10Fe2 cuboctahedra; edges with eight Mg(1,1)Mg8Fe2Cu2 cuboctahedra; faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra; faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra; faces with two equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; and faces with six equivalent Fe(1)Mg10Cu2 cuboctahedra. The Mg(4)-Mg(3) bond length is 3.03 Å. Both Mg(4)-Cu(1) bond lengths are 3.01 Å. In the seventh Mg site, Mg(3) is bonded in a 12-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Fe(1), and two equivalent Cu(1) atoms. Both Mg(3)-Mg(1) bond lengths are 3.05 Å. Both Mg(3)-Mg(2) bond lengths are 2.97 Å. There is one shorter (2.86 Å) and one longer (3.16 Å) Mg(3)-Mg(3) bond length. Both Mg(3)-Fe(1) bond lengths are 2.91 Å. There is one shorter (2.81 Å) and one longer (3.19 Å) Mg(3)-Cu(1) bond length. Fe(1) is bonded to two equivalent Mg(2); four Mg(1,1); four Mg(3,3); and two equivalent Cu(1) atoms to form FeMg10Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Fe2 cuboctahedra; corners with six equivalent Fe(1)Mg10Cu2 cuboctahedra; corners with eight Mg(1,1)Mg8Fe2Cu2 cuboctahedra; edges with two equivalent Mg(2)Mg10Fe2 cuboctahedra; edges with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; edges with four equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with two equivalent Mg(2)Mg10Fe2 cuboctahedra; faces with two equivalent Fe(1)Mg10Cu2 cuboctahedra; faces with two equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; and faces with six equivalent Mg(4)Mg10Cu2 cuboctahedra. Both Fe(1)-Cu(1) bond lengths are 2.89 Å. Cu(1) is bonded to two equivalent Mg(4); four Mg(1,1); four Mg(3,3,3); and two equivalent Fe(1) atoms to form CuMg10Fe2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Cu2 cuboctahedra; corners with six equivalent Cu(1)Mg10Fe2 cuboctahedra; edges with two equivalent Mg(4)Mg10Cu2 cuboctahedra; edges with four equivalent Fe(1)Mg10Cu2 cuboctahedra; edges with eight Mg(1,1)Mg8Fe2Cu2 cuboctahedra; faces with two equivalent Mg(4)Mg10Cu2 cuboctahedra; faces with two equivalent Fe(1)Mg10Cu2 cuboctahedra; faces with two equivalent Cu(1)Mg10Fe2 cuboctahedra; faces with four Mg(1,1)Mg8Fe2Cu2 cuboctahedra; and faces with six equivalent Mg(2)Mg10Fe2 cuboctahedra.