Cu15Si4 is Bergman Structure: Mg32(Al,Zn)49 Bergman-derived structured and crystallizes in the cubic I-43d space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to eight equivalent Cu(2) and four equivalent Si(1) atoms to form CuCu8Si4 cuboctahedra that share corners with eight equivalent Si(1)Cu12 cuboctahedra, edges with eight equivalent Cu(1)Cu8Si4 cuboctahedra, and faces with four equivalent Si(1)Cu12 cuboctahedra. In the second Cu site, Cu(2) is bonded in a 13-coordinate geometry to two equivalent Cu(1), eight equivalent Cu(2), and three equivalent Si(1) atoms. Si(1) is bonded to three equivalent Cu(1) and nine equivalent Cu(2) atoms to form SiCu12 cuboctahedra that share corners with six equivalent Cu(1)Cu8Si4 cuboctahedra, edges with six equivalent Si(1)Cu12 cuboctahedra, faces with three equivalent Cu(1)Cu8Si4 cuboctahedra, and faces with five equivalent Si(1)Cu12 cuboctahedra.
Cu15Si4 is Bergman Structure: Mg32(Al,Zn)49 Bergman-derived structured and crystallizes in the cubic I-43d space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to eight equivalent Cu(2) and four equivalent Si(1) atoms to form CuCu8Si4 cuboctahedra that share corners with eight equivalent Si(1)Cu12 cuboctahedra, edges with eight equivalent Cu(1)Cu8Si4 cuboctahedra, and faces with four equivalent Si(1)Cu12 cuboctahedra. There are four shorter (2.46 Å) and four longer (2.57 Å) Cu(1)-Cu(2) bond lengths. All Cu(1)-Si(1) bond lengths are 2.60 Å. In the second Cu site, Cu(2) is bonded in a 13-coordinate geometry to two equivalent Cu(1), eight equivalent Cu(2), and three equivalent Si(1) atoms. There are a spread of Cu(2)-Cu(2) bond distances ranging from 2.47-2.99 Å. There are a spread of Cu(2)-Si(1) bond distances ranging from 2.41-2.55 Å. Si(1) is bonded to three equivalent Cu(1) and nine equivalent Cu(2) atoms to form SiCu12 cuboctahedra that share corners with six equivalent Cu(1)Cu8Si4 cuboctahedra, edges with six equivalent Si(1)Cu12 cuboctahedra, faces with three equivalent Cu(1)Cu8Si4 cuboctahedra, and faces with five equivalent Si(1)Cu12 cuboctahedra.