DOE OSTI2020
Al3Er crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are three 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 ErAl12 cuboctahedra, corners with twelve equivalent AlEr4Al8 cuboctahedra, edges with six equivalent AlEr4Al8 cuboctahedra, faces with six equivalent AlEr4Al8 cuboctahedra, and faces with eight ErAl12 cuboctahedra. There are six shorter (3.03 Å) and six longer (3.06 Å) Er–Al bond lengths. In the second Er site, Er is bonded to twelve Al atoms to form ErAl12 cuboctahedra that share corners with six equivalent AlEr4Al8 cuboctahedra, corners with nine ErAl12 cuboctahedra, edges with twelve equivalent AlEr4Al8 cuboctahedra, faces with seven ErAl12 cuboctahedra, and faces with nine equivalent AlEr4Al8 cuboctahedra. There are a spread of Er–Al bond distances ranging from 3.01–3.03 Å. In the third Er site, Er is bonded to twelve Al atoms to form ErAl12 cuboctahedra that share corners with twelve ErAl12 cuboctahedra, edges with fifteen AlEr4Al8 cuboctahedra, faces with six ErAl12 cuboctahedra, and faces with six AlEr4Al8 cuboctahedra. There are a spread of Er–Al bond distances ranging from 2.97–3.04 Å. 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 ErAl12 cuboctahedra, corners with ten AlEr4Al8 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 2.94–3.06 Å. In the second Al site, Al is bonded in a 10-coordinate geometry to four Er and six Al atoms. There are two shorter (2.73 Å) and two longer (2.91 Å) Al–Al bond lengths. In the third Al site, Al is bonded to four Er and eight Al atoms to form distorted AlEr4Al8 cuboctahedra that share corners with four equivalent ErAl12 cuboctahedra, corners with fourteen AlEr4Al8 cuboctahedra, edges with four equivalent AlEr4Al8 cuboctahedra, edges with six ErAl12 cuboctahedra, faces with four ErAl12 cuboctahedra, and faces with six AlEr4Al8 cuboctahedra. All Al–Al bond lengths are 3.03 Å.