DOE OSTI2020
Nb3Mn8Al is Hexagonal Laves-derived structured and crystallizes in the trigonal P3m1 space group. The structure is three-dimensional. there are three inequivalent Nb sites. In the first Nb site, Nb is bonded in a 12-coordinate geometry to one Nb, twelve Mn, and three equivalent Al atoms. The Nb–Nb bond length is 2.98 Å. There are a spread of Nb–Mn bond distances ranging from 2.75–2.83 Å. All Nb–Al bond lengths are 2.91 Å. In the second Nb site, Nb is bonded in a 12-coordinate geometry to four Nb and twelve Mn atoms. All Nb–Nb bond lengths are 2.97 Å. There are a spread of Nb–Mn bond distances ranging from 2.79–2.83 Å. In the third Nb site, Nb is bonded in a 9-coordinate geometry to three equivalent Nb, twelve Mn, and one Al atom. There are a spread of Nb–Mn bond distances ranging from 2.75–2.90 Å. The Nb–Al bond length is 2.84 Å. There are four inequivalent Mn sites. In the first Mn site, Mn is bonded to three equivalent Nb, six Mn, and three equivalent Al atoms to form MnMn6Nb3Al3 cuboctahedra that share corners with twelve MnMn6Nb4Al2 cuboctahedra, edges with six equivalent MnMn6Nb3Al3 cuboctahedra, and faces with twenty MnMn6Nb6 cuboctahedra. There are three shorter (2.41 Å) and three longer (2.43 Å) Mn–Mn bond lengths. All Mn–Al bond lengths are 2.80 Å. In the second Mn site, Mn is bonded to six Nb and six Mn atoms to form MnMn6Nb6 cuboctahedra that share corners with twelve MnMn6Nb4Al2 cuboctahedra, edges with six equivalent MnMn6Nb6 cuboctahedra, and faces with twenty MnMn6Nb3Al3 cuboctahedra. There are three shorter (2.39 Å) and three longer (2.49 Å) Mn–Mn bond lengths. In the third Mn site, Mn is bonded to four Nb, six Mn, and two equivalent Al atoms to form MnMn6Nb4Al2 cuboctahedra that share corners with eighteen MnMn6Nb3Al3 cuboctahedra, edges with six MnMn6Nb4Al2 cuboctahedra, and faces with eighteen MnMn6Nb3Al3 cuboctahedra. There are two shorter (2.32 Å) and two longer (2.45 Å) Mn–Mn bond lengths. Both Mn–Al bond lengths are 2.80 Å. In the fourth Mn site, Mn is bonded to five Nb, six Mn, and one Al atom to form MnMn6Nb5Al cuboctahedra that share corners with eighteen MnMn6Nb3Al3 cuboctahedra, edges with six MnMn6Nb4Al2 cuboctahedra, and faces with eighteen MnMn6Nb3Al3 cuboctahedra. There are two shorter (2.29 Å) and two longer (2.48 Å) Mn–Mn bond lengths. The Mn–Al bond length is 2.78 Å. Al is bonded in a 12-coordinate geometry to four Nb and twelve Mn atoms.