DOE OSTI2020
Er4YAl15 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Er sites. In the first Er site, Er is bonded to twelve Al atoms to form ErAl12 cuboctahedra that share corners with six equivalent AlY2Er2Al8 cuboctahedra, corners with nine ErAl12 cuboctahedra, edges with twelve equivalent AlEr4Al8 cuboctahedra, a faceface with one YAl12 cuboctahedra, faces with six ErAl12 cuboctahedra, and faces with nine equivalent AlEr4Al8 cuboctahedra. There are a spread of Er–Al bond distances ranging from 3.01–3.04 Å. In the second Er site, Er is bonded to twelve Al atoms to form ErAl12 cuboctahedra that share corners with twelve ErAl12 cuboctahedra, edges with fifteen AlY2Er2Al8 cuboctahedra, faces with three equivalent ErAl12 cuboctahedra, faces with three equivalent YAl12 cuboctahedra, and faces with six AlEr4Al8 cuboctahedra. There are a spread of Er–Al bond distances ranging from 2.97–3.04 Å. Y is bonded to twelve Al atoms to form YAl12 cuboctahedra that share corners with six equivalent YAl12 cuboctahedra, corners with twelve equivalent AlEr4Al8 cuboctahedra, edges with six equivalent AlY2Er2Al8 cuboctahedra, faces with six equivalent AlY2Er2Al8 cuboctahedra, and faces with eight ErAl12 cuboctahedra. There are six shorter (3.04 Å) and six longer (3.07 Å) Y–Al bond lengths. There are three inequivalent Al sites. In the first Al site, Al is bonded to four Er and eight Al atoms to form distorted AlEr4Al8 cuboctahedra that share corners with two equivalent YAl12 cuboctahedra, corners with ten AlY2Er2Al8 cuboctahedra, edges with seven ErAl12 cuboctahedra, edges with eight equivalent AlEr4Al8 cuboctahedra, faces with four ErAl12 cuboctahedra, and faces with ten AlEr4Al8 cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.93–3.07 Å. In the second Al site, Al is bonded in a 10-coordinate geometry to three Er, one Y, and six Al atoms. There are two shorter (2.73 Å) and two longer (2.92 Å) Al–Al bond lengths. In the third Al site, Al is bonded to two equivalent Er, two equivalent Y, and eight Al atoms to form distorted AlY2Er2Al8 cuboctahedra that share corners with four equivalent ErAl12 cuboctahedra, corners with fourteen AlY2Er2Al8 cuboctahedra, edges with two equivalent YAl12 cuboctahedra, edges with four equivalent ErAl12 cuboctahedra, edges with four equivalent AlY2Er2Al8 cuboctahedra, faces with two equivalent ErAl12 cuboctahedra, faces with two equivalent YAl12 cuboctahedra, and faces with six AlEr4Al8 cuboctahedra. All Al–Al bond lengths are 3.04 Å.