Materials Data on MgAl2 by Materials Project
MgAl2 crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Mg is bonded to two equivalent Mg and ten Al atoms to form distorted MgMg2Al10 cuboctahedra that share corners with four equivalent AlMg4Al8 cuboctahedra, corners with eight equivalent MgMg2Al10 cuboctahedra, edges with four equivalent MgMg2Al10 cuboctahedra, edges with twelve equivalent AlMg4Al8 cuboctahedra, faces with five equivalent AlMg4Al8 cuboctahedra, and faces with seven equivalent MgMg2Al10 cuboctahedra. Both Mg–Mg bond lengths are 3.07 Å. There are a spread of Mg–Al bond distances ranging from 2.91–3.09 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded to four equivalent Mg and eight Al atoms to form AlMg4Al8 cuboctahedra that share corners with four equivalent MgMg2Al10 cuboctahedra, corners with four equivalent AlMg4Al8 cuboctahedra, edges with twelve equivalent MgMg2Al10 cuboctahedra, faces with five equivalent MgMg2Al10 cuboctahedra, and faces with eight equivalent AlMg4Al8 cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.91–2.95 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to six equivalent Mg and six Al atoms. Both Al–Al bond lengths are 3.11 Å.