Y5Cu5Mg16 crystallizes in the orthorhombic Cmcm space group. There are nine inequivalent Mg sites. In the first Mg site, Mg(9) is bonded in a distorted L-shaped geometry to two equivalent Cu(2) atoms. In the second Mg site, Mg(1) is bonded in a distorted single-bond geometry to two equivalent Mg(6) and one Cu(1) atom. In the third Mg site, Mg(2) is bonded in a water-like geometry to one Mg(6) and two equivalent Cu(1) atoms. In the fourth Mg site, Mg(3) is bonded in a distorted water-like geometry to two equivalent Cu(2) atoms. In the fifth Mg site, Mg(4) is bonded in a distorted single-bond geometry to three equivalent Mg(6) and one Cu(1) atom. In the sixth Mg site, Mg(5) is bonded in a 4-coordinate geometry to one Cu(1), one Cu(2), and two equivalent Cu(3) atoms. In the seventh Mg site, Mg(6) is bonded to one Mg(2), two equivalent Mg(1), two equivalent Mg(6), three equivalent Mg(4), three equivalent Mg(7), and one Y(2) atom to form distorted face-sharing MgYMg11 cuboctahedra. In the eighth Mg site, Mg(7) is bonded in a distorted single-bond geometry to three equivalent Mg(6) and one Cu(2) atom. In the ninth Mg site, Mg(8) is bonded in a distorted water-like geometry to two equivalent Cu(3) atoms. There are three inequivalent Y sites. In the first Y site, Y(1) is bonded in a 3-coordinate geometry to one Cu(3) and two equivalent Cu(1) atoms. In the second Y site, Y(2) is bonded in a 4-coordinate geometry to one Mg(6), two equivalent Cu(1), and two equivalent Cu(2) atoms. In the third Y site, Y(3) is bonded in a 5-coordinate geometry to one Cu(3) and four equivalent Cu(2) atoms. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), two equivalent Mg(2), two equivalent Y(1), and two equivalent Y(2) atoms. In the second Cu site, Cu(2) is bonded in a 9-coordinate geometry to one Mg(5), one Mg(7), one Mg(9), two equivalent Mg(3), two equivalent Y(2), and two equivalent Y(3) atoms. In the third Cu site, Cu(3) is bonded in a 9-coordinate geometry to two equivalent Mg(8), four equivalent Mg(5), one Y(3), and two equivalent Y(1) atoms.
Y5Cu5Mg16 crystallizes in the orthorhombic Cmcm space group. There are nine inequivalent Mg sites. In the first Mg site, Mg(9) is bonded in a distorted L-shaped geometry to two equivalent Cu(2) atoms. Both Mg(9)-Cu(2) bond lengths are 2.81 Å. In the second Mg site, Mg(1) is bonded in a distorted single-bond geometry to two equivalent Mg(6) and one Cu(1) atom. Both Mg(1)-Mg(6) bond lengths are 3.11 Å. The Mg(1)-Cu(1) bond length is 2.81 Å. In the third Mg site, Mg(2) is bonded in a water-like geometry to one Mg(6) and two equivalent Cu(1) atoms. The Mg(2)-Mg(6) bond length is 3.22 Å. Both Mg(2)-Cu(1) bond lengths are 2.71 Å. In the fourth Mg site, Mg(3) is bonded in a distorted water-like geometry to two equivalent Cu(2) atoms. Both Mg(3)-Cu(2) bond lengths are 2.73 Å. In the fifth Mg site, Mg(4) is bonded in a distorted single-bond geometry to three equivalent Mg(6) and one Cu(1) atom. There are two shorter (3.19 Å) and one longer (3.28 Å) Mg(4)-Mg(6) bond length. The Mg(4)-Cu(1) bond length is 2.80 Å. In the sixth Mg site, Mg(5) is bonded in a 4-coordinate geometry to one Cu(1), one Cu(2), and two equivalent Cu(3) atoms. The Mg(5)-Cu(1) bond length is 2.77 Å. The Mg(5)-Cu(2) bond length is 2.85 Å. Both Mg(5)-Cu(3) bond lengths are 2.75 Å. In the seventh Mg site, Mg(6) is bonded to one Mg(2), two equivalent Mg(1), two equivalent Mg(6), three equivalent Mg(4), three equivalent Mg(7), and one Y(2) atom to form distorted face-sharing MgYMg11 cuboctahedra. Both Mg(6)-Mg(6) bond lengths are 3.12 Å. There are two shorter (3.14 Å) and one longer (3.38 Å) Mg(6)-Mg(7) bond length. The Mg(6)-Y(2) bond length is 3.78 Å. In the eighth Mg site, Mg(7) is bonded in a distorted single-bond geometry to three equivalent Mg(6) and one Cu(2) atom. The Mg(7)-Cu(2) bond length is 2.78 Å. In the ninth Mg site, Mg(8) is bonded in a distorted water-like geometry to two equivalent Cu(3) atoms. Both Mg(8)-Cu(3) bond lengths are 2.74 Å. There are three inequivalent Y sites. In the first Y site, Y(1) is bonded in a 3-coordinate geometry to one Cu(3) and two equivalent Cu(1) atoms. The Y(1)-Cu(3) bond length is 3.06 Å. Both Y(1)-Cu(1) bond lengths are 2.99 Å. In the second Y site, Y(2) is bonded in a 4-coordinate geometry to one Mg(6), two equivalent Cu(1), and two equivalent Cu(2) atoms. Both Y(2)-Cu(1) bond lengths are 3.03 Å. Both Y(2)-Cu(2) bond lengths are 3.02 Å. In the third Y site, Y(3) is bonded in a 5-coordinate geometry to one Cu(3) and four equivalent Cu(2) atoms. The Y(3)-Cu(3) bond length is 2.98 Å. All Y(3)-Cu(2) bond lengths are 3.01 Å. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), two equivalent Mg(2), two equivalent Y(1), and two equivalent Y(2) atoms. In the second Cu site, Cu(2) is bonded in a 9-coordinate geometry to one Mg(5), one Mg(7), one Mg(9), two equivalent Mg(3), two equivalent Y(2), and two equivalent Y(3) atoms. In the third Cu site, Cu(3) is bonded in a 9-coordinate geometry to two equivalent Mg(8), four equivalent Mg(5), one Y(3), and two equivalent Y(1) atoms.