Lu3Cu11Si4 crystallizes in the hexagonal P6_3/mmc space group. Lu(1) is bonded in a 15-coordinate geometry to two equivalent Cu(1), two equivalent Cu(3), six equivalent Cu(2), one Si(2), and four equivalent Si(1) atoms. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent Lu(1), two equivalent Cu(1), two equivalent Cu(3), four equivalent Cu(2), and two equivalent Si(1) atoms to form distorted CuLu2Cu8Si2 cuboctahedra that share corners with four equivalent Cu(1)Lu2Cu8Si2 cuboctahedra, corners with four equivalent Si(1)Lu4Cu8 cuboctahedra, faces with two equivalent Cu(1)Lu2Cu8Si2 cuboctahedra, and faces with six equivalent Si(1)Lu4Cu8 cuboctahedra. In the second Cu site, Cu(2) is bonded in a 12-coordinate geometry to three equivalent Lu(1), one Cu(3), two equivalent Cu(1), three equivalent Cu(2), one Si(2), and two equivalent Si(1) atoms. In the third Cu site, Cu(3) is bonded in a 12-coordinate geometry to three equivalent Lu(1), three equivalent Cu(1), three equivalent Cu(2), and three equivalent Si(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(2) is bonded in a 9-coordinate geometry to three equivalent Lu(1) and six equivalent Cu(2) atoms. In the second Si site, Si(1) is bonded to four equivalent Lu(1), two equivalent Cu(1), two equivalent Cu(3), and four equivalent Cu(2) atoms to form SiLu4Cu8 cuboctahedra that share corners with four equivalent Cu(1)Lu2Cu8Si2 cuboctahedra, corners with four equivalent Si(1)Lu4Cu8 cuboctahedra, faces with six equivalent Cu(1)Lu2Cu8Si2 cuboctahedra, and faces with six equivalent Si(1)Lu4Cu8 cuboctahedra.
Lu3Cu11Si4 crystallizes in the hexagonal P6_3/mmc space group. Lu(1) is bonded in a 15-coordinate geometry to two equivalent Cu(1), two equivalent Cu(3), six equivalent Cu(2), one Si(2), and four equivalent Si(1) atoms. Both Lu(1)-Cu(1) bond lengths are 2.90 Å. Both Lu(1)-Cu(3) bond lengths are 2.91 Å. There are four shorter (2.93 Å) and two longer (2.98 Å) Lu(1)-Cu(2) bond lengths. The Lu(1)-Si(2) bond length is 2.87 Å. All Lu(1)-Si(1) bond lengths are 3.07 Å. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent Lu(1), two equivalent Cu(1), two equivalent Cu(3), four equivalent Cu(2), and two equivalent Si(1) atoms to form distorted CuLu2Cu8Si2 cuboctahedra that share corners with four equivalent Cu(1)Lu2Cu8Si2 cuboctahedra, corners with four equivalent Si(1)Lu4Cu8 cuboctahedra, faces with two equivalent Cu(1)Lu2Cu8Si2 cuboctahedra, and faces with six equivalent Si(1)Lu4Cu8 cuboctahedra. Both Cu(1)-Cu(1) bond lengths are 2.55 Å. Both Cu(1)-Cu(3) bond lengths are 2.56 Å. All Cu(1)-Cu(2) bond lengths are 2.65 Å. Both Cu(1)-Si(1) bond lengths are 2.32 Å. In the second Cu site, Cu(2) is bonded in a 12-coordinate geometry to three equivalent Lu(1), one Cu(3), two equivalent Cu(1), three equivalent Cu(2), one Si(2), and two equivalent Si(1) atoms. The Cu(2)-Cu(3) bond length is 2.72 Å. There are two shorter (2.67 Å) and one longer (2.72 Å) Cu(2)-Cu(2) bond length. The Cu(2)-Si(2) bond length is 2.57 Å. Both Cu(2)-Si(1) bond lengths are 2.64 Å. In the third Cu site, Cu(3) is bonded in a 12-coordinate geometry to three equivalent Lu(1), three equivalent Cu(1), three equivalent Cu(2), and three equivalent Si(1) atoms. All Cu(3)-Si(1) bond lengths are 2.40 Å. There are two inequivalent Si sites. In the first Si site, Si(2) is bonded in a 9-coordinate geometry to three equivalent Lu(1) and six equivalent Cu(2) atoms. In the second Si site, Si(1) is bonded to four equivalent Lu(1), two equivalent Cu(1), two equivalent Cu(3), and four equivalent Cu(2) atoms to form SiLu4Cu8 cuboctahedra that share corners with four equivalent Cu(1)Lu2Cu8Si2 cuboctahedra, corners with four equivalent Si(1)Lu4Cu8 cuboctahedra, faces with six equivalent Cu(1)Lu2Cu8Si2 cuboctahedra, and faces with six equivalent Si(1)Lu4Cu8 cuboctahedra.