LaCu9Mg2 crystallizes in the hexagonal P6_3/mmc space group. Mg(1) is bonded in a 12-coordinate geometry to three equivalent Cu(1) and nine equivalent Cu(4) atoms. La(1) is bonded in a distorted hexagonal planar geometry to three equivalent Cu(2), three equivalent Cu(3), and twelve equivalent Cu(4) atoms. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to six equivalent Mg(1) and six equivalent Cu(4) atoms to form CuMg6Cu6 cuboctahedra that share corners with twelve equivalent Cu(4)La2Mg3Cu7 cuboctahedra, edges with six equivalent Cu(1)Mg6Cu6 cuboctahedra, and faces with eighteen equivalent Cu(4)La2Mg3Cu7 cuboctahedra. In the second Cu site, Cu(2) is bonded in a 9-coordinate geometry to three equivalent La(1) and six equivalent Cu(4) atoms. In the third Cu site, Cu(3) is bonded in a 9-coordinate geometry to three equivalent La(1) and six equivalent Cu(4) atoms. In the fourth Cu site, Cu(4) is bonded to three equivalent Mg(1), two equivalent La(1), one Cu(1), one Cu(2), one Cu(3), and four equivalent Cu(4) atoms to form CuLa2Mg3Cu7 cuboctahedra that share corners with two equivalent Cu(1)Mg6Cu6 cuboctahedra, corners with fifteen equivalent Cu(4)La2Mg3Cu7 cuboctahedra, edges with eight equivalent Cu(4)La2Mg3Cu7 cuboctahedra, faces with three equivalent Cu(1)Mg6Cu6 cuboctahedra, and faces with eleven equivalent Cu(4)La2Mg3Cu7 cuboctahedra.
LaCu9Mg2 crystallizes in the hexagonal P6_3/mmc space group. Mg(1) is bonded in a 12-coordinate geometry to three equivalent Cu(1) and nine equivalent Cu(4) atoms. All Mg(1)-Cu(1) bond lengths are 2.95 Å. There are three shorter (2.83 Å) and six longer (2.92 Å) Mg(1)-Cu(4) bond lengths. La(1) is bonded in a distorted hexagonal planar geometry to three equivalent Cu(2), three equivalent Cu(3), and twelve equivalent Cu(4) atoms. All La(1)-Cu(2) bond lengths are 2.91 Å. All La(1)-Cu(3) bond lengths are 2.91 Å. All La(1)-Cu(4) bond lengths are 3.25 Å. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to six equivalent Mg(1) and six equivalent Cu(4) atoms to form CuMg6Cu6 cuboctahedra that share corners with twelve equivalent Cu(4)La2Mg3Cu7 cuboctahedra, edges with six equivalent Cu(1)Mg6Cu6 cuboctahedra, and faces with eighteen equivalent Cu(4)La2Mg3Cu7 cuboctahedra. All Cu(1)-Cu(4) bond lengths are 2.44 Å. In the second Cu site, Cu(2) is bonded in a 9-coordinate geometry to three equivalent La(1) and six equivalent Cu(4) atoms. All Cu(2)-Cu(4) bond lengths are 2.52 Å. In the third Cu site, Cu(3) is bonded in a 9-coordinate geometry to three equivalent La(1) and six equivalent Cu(4) atoms. All Cu(3)-Cu(4) bond lengths are 2.51 Å. In the fourth Cu site, Cu(4) is bonded to three equivalent Mg(1), two equivalent La(1), one Cu(1), one Cu(2), one Cu(3), and four equivalent Cu(4) atoms to form CuLa2Mg3Cu7 cuboctahedra that share corners with two equivalent Cu(1)Mg6Cu6 cuboctahedra, corners with fifteen equivalent Cu(4)La2Mg3Cu7 cuboctahedra, edges with eight equivalent Cu(4)La2Mg3Cu7 cuboctahedra, faces with three equivalent Cu(1)Mg6Cu6 cuboctahedra, and faces with eleven equivalent Cu(4)La2Mg3Cu7 cuboctahedra. There are two shorter (2.50 Å) and two longer (2.53 Å) Cu(4)-Cu(4) bond lengths.