DOE OSTI2020
TaFe4Al is Hexagonal Laves-derived structured and crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to three equivalent Ta, twelve Fe, and one Al atom. All Ta–Ta bond lengths are 3.00 Å. There are a spread of Ta–Fe bond distances ranging from 2.74–2.87 Å. The Ta–Al bond length is 2.83 Å. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded to six equivalent Fe and six equivalent Al atoms to form FeAl6Fe6 cuboctahedra that share corners with twelve equivalent FeTa3Al3Fe6 cuboctahedra, edges with six equivalent FeAl6Fe6 cuboctahedra, and faces with twenty FeTa6Fe6 cuboctahedra. All Fe–Fe bond lengths are 2.37 Å. All Fe–Al bond lengths are 2.79 Å. In the second Fe site, Fe is bonded to six equivalent Ta and six equivalent Fe atoms to form FeTa6Fe6 cuboctahedra that share corners with twelve equivalent FeTa3Al3Fe6 cuboctahedra, edges with six equivalent FeTa6Fe6 cuboctahedra, and faces with twenty FeAl6Fe6 cuboctahedra. All Fe–Fe bond lengths are 2.39 Å. In the third Fe site, Fe is bonded to three equivalent Ta, six Fe, and three equivalent Al atoms to form FeTa3Al3Fe6 cuboctahedra that share corners with eighteen FeAl6Fe6 cuboctahedra, edges with six equivalent FeTa3Al3Fe6 cuboctahedra, and faces with eighteen FeAl6Fe6 cuboctahedra. There are two shorter (2.35 Å) and two longer (2.43 Å) Fe–Fe bond lengths. There are one shorter (2.70 Å) and two longer (2.81 Å) Fe–Al bond lengths. Al is bonded in a 12-coordinate geometry to one Ta, twelve Fe, and three equivalent Al atoms. All Al–Al bond lengths are 2.89 Å.