NbFe4Si crystallizes in the trigonal P-3m1 space group. Nb(1) is bonded in a 16-coordinate geometry to three equivalent Nb(1), three equivalent Fe(1), nine equivalent Fe(3), and one Si(1) atom. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to six equivalent Nb(1) and six equivalent Fe(3) atoms to form FeNb6Fe6 cuboctahedra that share corners with twelve equivalent Fe(3)Nb3Fe6Si3 cuboctahedra, edges with six equivalent Fe(1)Nb6Fe6 cuboctahedra, faces with two equivalent Fe(2)Fe6Si6 cuboctahedra, and faces with eighteen equivalent Fe(3)Nb3Fe6Si3 cuboctahedra. In the second Fe site, Fe(2) is bonded to six equivalent Fe(3) and six equivalent Si(1) atoms to form FeFe6Si6 cuboctahedra that share corners with twelve equivalent Fe(3)Nb3Fe6Si3 cuboctahedra, edges with six equivalent Fe(2)Fe6Si6 cuboctahedra, faces with two equivalent Fe(1)Nb6Fe6 cuboctahedra, and faces with eighteen equivalent Fe(3)Nb3Fe6Si3 cuboctahedra. In the third Fe site, Fe(3) is bonded to three equivalent Nb(1), one Fe(1), one Fe(2), four equivalent Fe(3), and three equivalent Si(1) atoms to form FeNb3Fe6Si3 cuboctahedra that share corners with two equivalent Fe(2)Fe6Si6 cuboctahedra, corners with two equivalent Fe(1)Nb6Fe6 cuboctahedra, corners with fourteen equivalent Fe(3)Nb3Fe6Si3 cuboctahedra, edges with six equivalent Fe(3)Nb3Fe6Si3 cuboctahedra, faces with three equivalent Fe(2)Fe6Si6 cuboctahedra, faces with three equivalent Fe(1)Nb6Fe6 cuboctahedra, and faces with twelve equivalent Fe(3)Nb3Fe6Si3 cuboctahedra. Si(1) is bonded in a 13-coordinate geometry to one Nb(1), three equivalent Fe(2), and nine equivalent Fe(3) atoms.
NbFe4Si crystallizes in the trigonal P-3m1 space group. Nb(1) is bonded in a 16-coordinate geometry to three equivalent Nb(1), three equivalent Fe(1), nine equivalent Fe(3), and one Si(1) atom. All Nb(1)-Nb(1) bond lengths are 3.03 Å. All Nb(1)-Fe(1) bond lengths are 2.83 Å. There are six shorter (2.73 Å) and three longer (2.89 Å) Nb(1)-Fe(3) bond lengths. The Nb(1)-Si(1) bond length is 2.72 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to six equivalent Nb(1) and six equivalent Fe(3) atoms to form FeNb6Fe6 cuboctahedra that share corners with twelve equivalent Fe(3)Nb3Fe6Si3 cuboctahedra, edges with six equivalent Fe(1)Nb6Fe6 cuboctahedra, faces with two equivalent Fe(2)Fe6Si6 cuboctahedra, and faces with eighteen equivalent Fe(3)Nb3Fe6Si3 cuboctahedra. All Fe(1)-Fe(3) bond lengths are 2.40 Å. In the second Fe site, Fe(2) is bonded to six equivalent Fe(3) and six equivalent Si(1) atoms to form FeFe6Si6 cuboctahedra that share corners with twelve equivalent Fe(3)Nb3Fe6Si3 cuboctahedra, edges with six equivalent Fe(2)Fe6Si6 cuboctahedra, faces with two equivalent Fe(1)Nb6Fe6 cuboctahedra, and faces with eighteen equivalent Fe(3)Nb3Fe6Si3 cuboctahedra. All Fe(2)-Fe(3) bond lengths are 2.31 Å. All Fe(2)-Si(1) bond lengths are 2.80 Å. In the third Fe site, Fe(3) is bonded to three equivalent Nb(1), one Fe(1), one Fe(2), four equivalent Fe(3), and three equivalent Si(1) atoms to form FeNb3Fe6Si3 cuboctahedra that share corners with two equivalent Fe(2)Fe6Si6 cuboctahedra, corners with two equivalent Fe(1)Nb6Fe6 cuboctahedra, corners with fourteen equivalent Fe(3)Nb3Fe6Si3 cuboctahedra, edges with six equivalent Fe(3)Nb3Fe6Si3 cuboctahedra, faces with three equivalent Fe(2)Fe6Si6 cuboctahedra, faces with three equivalent Fe(1)Nb6Fe6 cuboctahedra, and faces with twelve equivalent Fe(3)Nb3Fe6Si3 cuboctahedra. There are two shorter (2.35 Å) and two longer (2.44 Å) Fe(3)-Fe(3) bond lengths. There is one shorter (2.64 Å) and two longer (2.78 Å) Fe(3)-Si(1) bond lengths. Si(1) is bonded in a 13-coordinate geometry to one Nb(1), three equivalent Fe(2), and nine equivalent Fe(3) atoms.