Al3Mg is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. Mg(1) is bonded to four equivalent Al(1) and eight equivalent Al(2) atoms to form MgAl12 cuboctahedra that share corners with four equivalent Mg(1)Al12 cuboctahedra, corners with eight equivalent Al(1)Mg4Al8 cuboctahedra, edges with eight equivalent Mg(1)Al12 cuboctahedra, edges with sixteen equivalent Al(2)Mg4Al8 cuboctahedra, faces with four equivalent Mg(1)Al12 cuboctahedra, faces with six equivalent Al(1)Mg4Al8 cuboctahedra, and faces with eight equivalent Al(2)Mg4Al8 cuboctahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to four equivalent Mg(1) and eight equivalent Al(2) atoms to form AlMg4Al8 cuboctahedra that share corners with four equivalent Al(1)Mg4Al8 cuboctahedra, corners with eight equivalent Mg(1)Al12 cuboctahedra, edges with eight equivalent Al(1)Mg4Al8 cuboctahedra, edges with sixteen equivalent Al(2)Mg4Al8 cuboctahedra, faces with four equivalent Al(1)Mg4Al8 cuboctahedra, faces with six equivalent Mg(1)Al12 cuboctahedra, and faces with eight equivalent Al(2)Mg4Al8 cuboctahedra. In the second Al site, Al(2) is bonded to four equivalent Mg(1), four equivalent Al(1), and four equivalent Al(2) atoms to form AlMg4Al8 cuboctahedra that share corners with twelve equivalent Al(2)Mg4Al8 cuboctahedra, edges with eight equivalent Mg(1)Al12 cuboctahedra, edges with eight equivalent Al(1)Mg4Al8 cuboctahedra, edges with eight equivalent Al(2)Mg4Al8 cuboctahedra, faces with four equivalent Mg(1)Al12 cuboctahedra, faces with four equivalent Al(1)Mg4Al8 cuboctahedra, and faces with ten equivalent Al(2)Mg4Al8 cuboctahedra.
Al3Mg is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. Mg(1) is bonded to four equivalent Al(1) and eight equivalent Al(2) atoms to form MgAl12 cuboctahedra that share corners with four equivalent Mg(1)Al12 cuboctahedra, corners with eight equivalent Al(1)Mg4Al8 cuboctahedra, edges with eight equivalent Mg(1)Al12 cuboctahedra, edges with sixteen equivalent Al(2)Mg4Al8 cuboctahedra, faces with four equivalent Mg(1)Al12 cuboctahedra, faces with six equivalent Al(1)Mg4Al8 cuboctahedra, and faces with eight equivalent Al(2)Mg4Al8 cuboctahedra. All Mg(1)-Al(1) bond lengths are 2.89 Å. All Mg(1)-Al(2) bond lengths are 2.90 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to four equivalent Mg(1) and eight equivalent Al(2) atoms to form AlMg4Al8 cuboctahedra that share corners with four equivalent Al(1)Mg4Al8 cuboctahedra, corners with eight equivalent Mg(1)Al12 cuboctahedra, edges with eight equivalent Al(1)Mg4Al8 cuboctahedra, edges with sixteen equivalent Al(2)Mg4Al8 cuboctahedra, faces with four equivalent Al(1)Mg4Al8 cuboctahedra, faces with six equivalent Mg(1)Al12 cuboctahedra, and faces with eight equivalent Al(2)Mg4Al8 cuboctahedra. All Al(1)-Al(2) bond lengths are 2.90 Å. In the second Al site, Al(2) is bonded to four equivalent Mg(1), four equivalent Al(1), and four equivalent Al(2) atoms to form AlMg4Al8 cuboctahedra that share corners with twelve equivalent Al(2)Mg4Al8 cuboctahedra, edges with eight equivalent Mg(1)Al12 cuboctahedra, edges with eight equivalent Al(1)Mg4Al8 cuboctahedra, edges with eight equivalent Al(2)Mg4Al8 cuboctahedra, faces with four equivalent Mg(1)Al12 cuboctahedra, faces with four equivalent Al(1)Mg4Al8 cuboctahedra, and faces with ten equivalent Al(2)Mg4Al8 cuboctahedra. All Al(2)-Al(2) bond lengths are 2.89 Å.