Materials Data on Nb6Fe7 by Materials Project
Fe7Nb6 is Frank-Kasper $\mu$ Phase structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are three inequivalent Nb sites. In the first Nb site, Nb is bonded in a 9-coordinate geometry to nine Nb and six equivalent Fe atoms. There are a spread of Nb–Nb bond distances ranging from 2.82–3.12 Å. All Nb–Fe bond lengths are 2.80 Å. In the second Nb site, Nb is bonded in a 6-coordinate geometry to four Nb and twelve Fe atoms. There are one shorter (2.72 Å) and three longer (2.90 Å) Nb–Nb bond lengths. There are a spread of Nb–Fe bond distances ranging from 2.70–2.93 Å. In the third Nb site, Nb is bonded in a 8-coordinate geometry to eight Nb and six equivalent Fe atoms. The Nb–Nb bond length is 2.65 Å. All Nb–Fe bond lengths are 2.68 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six equivalent Nb and six equivalent Fe atoms to form FeNb6Fe6 cuboctahedra that share corners with twelve equivalent FeNb7Fe5 cuboctahedra, edges with six equivalent FeNb6Fe6 cuboctahedra, and faces with eighteen equivalent FeNb7Fe5 cuboctahedra. All Fe–Fe bond lengths are 2.41 Å. In the second Fe site, Fe is bonded to seven Nb and five Fe atoms to form FeNb7Fe5 cuboctahedra that share corners with fifteen FeNb6Fe6 cuboctahedra, edges with five equivalent FeNb7Fe5 cuboctahedra, and faces with thirteen FeNb6Fe6 cuboctahedra. There are two shorter (2.42 Å) and two longer (2.47 Å) Fe–Fe bond lengths.