Materials Data on Nb3AlCr8 by Materials Project

Nb3Cr8Al is Hexagonal Laves-derived structured and crystallizes in the trigonal R3m 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 four Nb and twelve Cr atoms. There are three shorter (3.00 Å) and one longer (3.01 Å) Nb–Nb bond lengths. There are three shorter (2.86 Å) and nine longer (2.87 Å) Nb–Cr bond lengths. In the second Nb site, Nb is bonded in a 12-coordinate geometry to three equivalent Nb, twelve Cr, and one Al atom. There are a spread of Nb–Cr bond distances ranging from 2.85–2.91 Å. The Nb–Al bond length is 2.95 Å. In the third Nb site, Nb is bonded in a 12-coordinate geometry to one Nb, twelve Cr, and three equivalent Al atoms. There are a spread of Nb–Cr bond distances ranging from 2.82–2.87 Å. All Nb–Al bond lengths are 2.98 Å. There are four inequivalent Cr sites. In the first Cr site, Cr is bonded to four Nb, six Cr, and two equivalent Al atoms to form a mixture of edge, face, and corner-sharing CrNb4Al2Cr6 cuboctahedra. There are a spread of Cr–Cr bond distances ranging from 2.43–2.45 Å. Both Cr–Al bond lengths are 2.85 Å. In the second Cr site, Cr is bonded to five Nb, six Cr, and one Al atom to form a mixture of edge, face, and corner-sharing CrNb5AlCr6 cuboctahedra. There are three shorter (2.43 Å) and three longer (2.45 Å) Cr–Cr bond lengths. The Cr–Al bond length is 2.84 Å. In the third Cr site, Cr is bonded to three equivalent Nb, six Cr, and three equivalent Al atoms to form CrNb3Al3Cr6 cuboctahedra that share corners with eighteen CrNb4Al2Cr6 cuboctahedra, edges with six equivalent CrNb3Al3Cr6 cuboctahedra, and faces with eighteen CrNb4Al2Cr6 cuboctahedra. All Cr–Al bond lengths are 2.86 Å. In the fourth Cr site, Cr is bonded to six Nb and six Cr atoms to form CrNb6Cr6 cuboctahedra that share corners with eighteen CrNb4Al2Cr6 cuboctahedra, edges with six equivalent CrNb6Cr6 cuboctahedra, and faces with eighteen CrNb4Al2Cr6 cuboctahedra. Al is bonded in a 12-coordinate geometry to four Nb and twelve Cr atoms.