MgCu3 is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. Mg(1) is bonded to four equivalent Cu(1) and eight equivalent Cu(2) atoms to form MgCu12 cuboctahedra that share corners with four equivalent Mg(1)Cu12 cuboctahedra, corners with eight equivalent Cu(1)Mg4Cu8 cuboctahedra, edges with eight equivalent Mg(1)Cu12 cuboctahedra, edges with sixteen equivalent Cu(2)Mg4Cu8 cuboctahedra, faces with four equivalent Mg(1)Cu12 cuboctahedra, faces with six equivalent Cu(1)Mg4Cu8 cuboctahedra, and faces with eight equivalent Cu(2)Mg4Cu8 cuboctahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to four equivalent Mg(1) and eight equivalent Cu(2) atoms to form distorted CuMg4Cu8 cuboctahedra that share corners with four equivalent Cu(1)Mg4Cu8 cuboctahedra, corners with eight equivalent Mg(1)Cu12 cuboctahedra, edges with eight equivalent Cu(1)Mg4Cu8 cuboctahedra, edges with sixteen equivalent Cu(2)Mg4Cu8 cuboctahedra, faces with four equivalent Cu(1)Mg4Cu8 cuboctahedra, faces with six equivalent Mg(1)Cu12 cuboctahedra, and faces with eight equivalent Cu(2)Mg4Cu8 cuboctahedra. In the second Cu site, Cu(2) is bonded to four equivalent Mg(1), four equivalent Cu(1), and four equivalent Cu(2) atoms to form distorted CuMg4Cu8 cuboctahedra that share corners with twelve equivalent Cu(2)Mg4Cu8 cuboctahedra, edges with eight equivalent Mg(1)Cu12 cuboctahedra, edges with eight equivalent Cu(1)Mg4Cu8 cuboctahedra, edges with eight equivalent Cu(2)Mg4Cu8 cuboctahedra, faces with four equivalent Mg(1)Cu12 cuboctahedra, faces with four equivalent Cu(1)Mg4Cu8 cuboctahedra, and faces with ten equivalent Cu(2)Mg4Cu8 cuboctahedra.
MgCu3 is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. Mg(1) is bonded to four equivalent Cu(1) and eight equivalent Cu(2) atoms to form MgCu12 cuboctahedra that share corners with four equivalent Mg(1)Cu12 cuboctahedra, corners with eight equivalent Cu(1)Mg4Cu8 cuboctahedra, edges with eight equivalent Mg(1)Cu12 cuboctahedra, edges with sixteen equivalent Cu(2)Mg4Cu8 cuboctahedra, faces with four equivalent Mg(1)Cu12 cuboctahedra, faces with six equivalent Cu(1)Mg4Cu8 cuboctahedra, and faces with eight equivalent Cu(2)Mg4Cu8 cuboctahedra. All Mg(1)-Cu(1) bond lengths are 2.63 Å. All Mg(1)-Cu(2) bond lengths are 2.63 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to four equivalent Mg(1) and eight equivalent Cu(2) atoms to form distorted CuMg4Cu8 cuboctahedra that share corners with four equivalent Cu(1)Mg4Cu8 cuboctahedra, corners with eight equivalent Mg(1)Cu12 cuboctahedra, edges with eight equivalent Cu(1)Mg4Cu8 cuboctahedra, edges with sixteen equivalent Cu(2)Mg4Cu8 cuboctahedra, faces with four equivalent Cu(1)Mg4Cu8 cuboctahedra, faces with six equivalent Mg(1)Cu12 cuboctahedra, and faces with eight equivalent Cu(2)Mg4Cu8 cuboctahedra. All Cu(1)-Cu(2) bond lengths are 2.63 Å. In the second Cu site, Cu(2) is bonded to four equivalent Mg(1), four equivalent Cu(1), and four equivalent Cu(2) atoms to form distorted CuMg4Cu8 cuboctahedra that share corners with twelve equivalent Cu(2)Mg4Cu8 cuboctahedra, edges with eight equivalent Mg(1)Cu12 cuboctahedra, edges with eight equivalent Cu(1)Mg4Cu8 cuboctahedra, edges with eight equivalent Cu(2)Mg4Cu8 cuboctahedra, faces with four equivalent Mg(1)Cu12 cuboctahedra, faces with four equivalent Cu(1)Mg4Cu8 cuboctahedra, and faces with ten equivalent Cu(2)Mg4Cu8 cuboctahedra. All Cu(2)-Cu(2) bond lengths are 2.63 Å.