Materials Data on Mg3(TaAl9)2 by Materials Project
Mg3(TaAl9)2 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 12-coordinate geometry to two equivalent Mg and twelve equivalent Al atoms. Both Mg–Mg bond lengths are 3.22 Å. All Mg–Al bond lengths are 3.17 Å. In the second Mg site, Mg is bonded in a 12-coordinate geometry to four equivalent Mg and twelve equivalent Al atoms. All Mg–Al bond lengths are 3.27 Å. Ta is bonded to twelve Al atoms to form TaAl12 cuboctahedra that share corners with six equivalent TaAl12 cuboctahedra, edges with eighteen equivalent AlMg3TaAl8 cuboctahedra, and faces with six equivalent AlMg3TaAl8 cuboctahedra. There are six shorter (2.64 Å) and six longer (2.89 Å) Ta–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 2-coordinate geometry to two equivalent Ta and ten Al atoms. There are a spread of Al–Al bond distances ranging from 2.78–2.93 Å. In the second Al site, Al is bonded to three Mg, one Ta, and eight Al atoms to form AlMg3TaAl8 cuboctahedra that share corners with fifteen equivalent AlMg3TaAl8 cuboctahedra, edges with two equivalent AlMg3TaAl8 cuboctahedra, edges with three equivalent TaAl12 cuboctahedra, a faceface with one TaAl12 cuboctahedra, and faces with fifteen equivalent AlMg3TaAl8 cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.78–3.02 Å.