DOE OSTI2020
Ta3Mn8Al crystallizes in the trigonal P3m1 space group. The structure is three-dimensional. there are three inequivalent Ta sites. In the first Ta site, Ta is bonded in a 9-coordinate geometry to one Ta, twelve Mn, and three equivalent Al atoms. The Ta–Ta bond length is 2.97 Å. There are a spread of Ta–Mn bond distances ranging from 2.76–2.82 Å. All Ta–Al bond lengths are 2.92 Å. In the second Ta site, Ta is bonded in a 12-coordinate geometry to four Ta and twelve Mn atoms. All Ta–Ta bond lengths are 2.97 Å. There are a spread of Ta–Mn bond distances ranging from 2.79–2.83 Å. In the third Ta site, Ta is bonded in a 10-coordinate geometry to three equivalent Ta, twelve Mn, and one Al atom. There are a spread of Ta–Mn bond distances ranging from 2.76–2.89 Å. The Ta–Al bond length is 2.85 Å. There are four inequivalent Mn sites. In the first Mn site, Mn is bonded to three equivalent Ta, six Mn, and three equivalent Al atoms to form MnTa3Mn6Al3 cuboctahedra that share corners with twelve MnTa4Mn6Al2 cuboctahedra, edges with six equivalent MnTa3Mn6Al3 cuboctahedra, and faces with twenty MnTa6Mn6 cuboctahedra. There are three shorter (2.41 Å) and three longer (2.44 Å) Mn–Mn bond lengths. All Mn–Al bond lengths are 2.80 Å. In the second Mn site, Mn is bonded to six Ta and six Mn atoms to form MnTa6Mn6 cuboctahedra that share corners with twelve MnTa4Mn6Al2 cuboctahedra, edges with six equivalent MnTa6Mn6 cuboctahedra, and faces with twenty MnTa3Mn6Al3 cuboctahedra. There are three shorter (2.40 Å) and three longer (2.48 Å) Mn–Mn bond lengths. In the third Mn site, Mn is bonded to four Ta, six Mn, and two equivalent Al atoms to form MnTa4Mn6Al2 cuboctahedra that share corners with eighteen MnTa3Mn6Al3 cuboctahedra, edges with six MnTa5Mn6Al cuboctahedra, and faces with eighteen MnTa3Mn6Al3 cuboctahedra. There are two shorter (2.31 Å) and two longer (2.46 Å) Mn–Mn bond lengths. Both Mn–Al bond lengths are 2.80 Å. In the fourth Mn site, Mn is bonded to five Ta, six Mn, and one Al atom to form MnTa5Mn6Al cuboctahedra that share corners with eighteen MnTa3Mn6Al3 cuboctahedra, edges with six MnTa5Mn6Al cuboctahedra, and faces with eighteen MnTa3Mn6Al3 cuboctahedra. There are two shorter (2.29 Å) and two longer (2.48 Å) Mn–Mn bond lengths. The Mn–Al bond length is 2.79 Å. Al is bonded in a 1-coordinate geometry to four Ta and twelve Mn atoms.