DOE OSTI2020
Al3GeTi crystallizes in the tetragonal P4mm space group. The structure is three-dimensional. Ti is bonded to four equivalent Ti, six Al, and two equivalent Ge atoms to form distorted TiTi4Al6Ge2 cuboctahedra that share corners with four equivalent TiTi4Al6Ge2 cuboctahedra, corners with four equivalent AlAl10Ge2 cuboctahedra, corners with two equivalent AlAl4Ge5 square pyramids, edges with twelve AlTi4Al8 cuboctahedra, faces with five AlTi4Al8 cuboctahedra, and faces with eight equivalent TiTi4Al6Ge2 cuboctahedra. All Ti–Ti bond lengths are 2.83 Å. There are two shorter (2.83 Å) and four longer (2.85 Å) Ti–Al bond lengths. Both Ti–Ge bond lengths are 2.73 Å. There are five inequivalent Al sites. In the first Al site, Al is bonded to four equivalent Al and five Ge atoms to form distorted AlAl4Ge5 square pyramids that share corners with four equivalent TiTi4Al6Ge2 cuboctahedra, corners with four equivalent AlTi4Al8 cuboctahedra, corners with four equivalent AlAl4Ge5 square pyramids, edges with twelve AlTi4Al8 cuboctahedra, faces with five AlTi4Al8 cuboctahedra, and faces with four equivalent AlAl4Ge5 square pyramids. All Al–Al bond lengths are 2.91 Å. There are one shorter (2.54 Å) and four longer (2.84 Å) Al–Ge bond lengths. In the second Al site, Al is bonded in a 5-coordinate geometry to four equivalent Ti and five Ge atoms. There are one shorter (2.57 Å) and four longer (2.84 Å) Al–Ge bond lengths. In the third Al site, Al is bonded to four equivalent Ti and eight Al atoms to form AlTi4Al8 cuboctahedra that share corners with four equivalent AlTi4Al8 cuboctahedra, corners with four equivalent AlAl4Ge5 square pyramids, edges with eight equivalent TiTi4Al6Ge2 cuboctahedra, edges with eight equivalent AlAl10Ge2 cuboctahedra, faces with four equivalent TiTi4Al6Ge2 cuboctahedra, faces with twelve AlTi4Al8 cuboctahedra, and a faceface with one AlAl4Ge5 square pyramid. There are four shorter (2.83 Å) and four longer (2.88 Å) Al–Al bond lengths. In the fourth Al site, Al is bonded to four equivalent Ti and eight Al atoms to form AlTi4Al8 cuboctahedra that share corners with four equivalent AlTi4Al8 cuboctahedra, edges with eight equivalent TiTi4Al6Ge2 cuboctahedra, edges with eight equivalent AlAl10Ge2 cuboctahedra, edges with four equivalent AlAl4Ge5 square pyramids, faces with four equivalent TiTi4Al6Ge2 cuboctahedra, and faces with twelve AlTi4Al8 cuboctahedra. All Al–Al bond lengths are 2.88 Å. In the fifth Al site, Al is bonded to ten Al and two equivalent Ge atoms to form distorted AlAl10Ge2 cuboctahedra that share corners with four equivalent TiTi4Al6Ge2 cuboctahedra, corners with four equivalent AlAl10Ge2 cuboctahedra, edges with four equivalent TiTi4Al6Ge2 cuboctahedra, edges with eight AlTi4Al8 cuboctahedra, edges with four equivalent AlAl4Ge5 square pyramids, a faceface with one TiTi4Al6Ge2 cuboctahedra, faces with twelve AlTi4Al8 cuboctahedra, and faces with two equivalent AlAl4Ge5 square pyramids. All Al–Al bond lengths are 2.83 Å. Both Al–Ge bond lengths are 2.78 Å. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Ti and five Al atoms. In the second Ge site, Ge is bonded in a 9-coordinate geometry to nine Al atoms.