FeAlNb crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 16-coordinate geometry to one Nb(1), three equivalent Nb(2), one Fe(3), two equivalent Fe(1), two equivalent Fe(2), three equivalent Al(1), and four equivalent Al(2) atoms. In the second Nb site, Nb(2) is bonded in a 16-coordinate geometry to one Nb(2); three Nb(1,1); one Fe(1); two equivalent Fe(3); four equivalent Fe(2); two equivalent Al(2); and three equivalent Al(1) atoms. In the third Nb site, Nb(1) is bonded in a 16-coordinate geometry to one Nb(1), three equivalent Nb(2), one Fe(3), two equivalent Fe(1), two equivalent Fe(2), three equivalent Al(1), and four equivalent Al(2) atoms. In the fourth Nb site, Nb(1) is bonded in a 16-coordinate geometry to one Nb(1), three equivalent Nb(2), one Fe(3), two equivalent Fe(1), two equivalent Fe(2), three equivalent Al(1), and four equivalent Al(2) atoms. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Nb(2); four Nb(1,1); two equivalent Al(1); and four equivalent Al(2) atoms to form distorted FeNb6Al6 cuboctahedra that share corners with two equivalent Fe(3)Nb6Al2Fe4 cuboctahedra, corners with four equivalent Fe(1)Nb6Al6 cuboctahedra, corners with eight equivalent Fe(2)Nb6Al2Fe4 cuboctahedra, edges with two equivalent Fe(1)Nb6Al6 cuboctahedra, edges with four equivalent Fe(3)Nb6Al2Fe4 cuboctahedra, and faces with four equivalent Fe(2)Nb6Al2Fe4 cuboctahedra. In the second Fe site, Fe(2) is bonded to two Nb(1,1); four equivalent Nb(2); two equivalent Fe(2); two equivalent Fe(3); and two equivalent Al(1) atoms to form distorted FeNb6Al2Fe4 cuboctahedra that share corners with four equivalent Fe(2)Nb6Al2Fe4 cuboctahedra, corners with four equivalent Fe(1)Nb6Al6 cuboctahedra, edges with two equivalent Fe(2)Nb6Al2Fe4 cuboctahedra, faces with two equivalent Fe(1)Nb6Al6 cuboctahedra, faces with four equivalent Fe(2)Nb6Al2Fe4 cuboctahedra, and faces with four equivalent Fe(3)Nb6Al2Fe4 cuboctahedra. In the third Fe site, Fe(3) is bonded to two Nb(1,1); four equivalent Nb(2); four equivalent Fe(2); and two equivalent Al(1) atoms to form distorted FeNb6Al2Fe4 cuboctahedra that share corners with two equivalent Fe(1)Nb6Al6 cuboctahedra, corners with four equivalent Fe(3)Nb6Al2Fe4 cuboctahedra, edges with two equivalent Fe(3)Nb6Al2Fe4 cuboctahedra, edges with four equivalent Fe(1)Nb6Al6 cuboctahedra, and faces with eight equivalent Fe(2)Nb6Al2Fe4 cuboctahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 4-coordinate geometry to three Nb(1,1); three equivalent Nb(2); one Fe(1); one Fe(3); two equivalent Fe(2); and two equivalent Al(2) atoms. In the second Al site, Al(2) is bonded in a 12-coordinate geometry to two equivalent Nb(2); four Nb(1,1,1); two equivalent Fe(1); two equivalent Al(1); and two equivalent Al(2) atoms.
FeAlNb crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 16-coordinate geometry to one Nb(1), three equivalent Nb(2), one Fe(3), two equivalent Fe(1), two equivalent Fe(2), three equivalent Al(1), and four equivalent Al(2) atoms. The Nb(1)-Nb(1) bond length is 3.20 Å. There is one shorter (3.00 Å) and two longer (3.05 Å) Nb(1)-Nb(2) bond lengths. The Nb(1)-Fe(3) bond length is 2.85 Å. Both Nb(1)-Fe(1) bond lengths are 2.96 Å. Both Nb(1)-Fe(2) bond lengths are 2.83 Å. There are two shorter (2.88 Å) and one longer (2.95 Å) Nb(1)-Al(1) bond length. There are two shorter (2.92 Å) and two longer (2.96 Å) Nb(1)-Al(2) bond lengths. In the second Nb site, Nb(2) is bonded in a 16-coordinate geometry to one Nb(2); three Nb(1,1); one Fe(1); two equivalent Fe(3); four equivalent Fe(2); two equivalent Al(2); and three equivalent Al(1) atoms. The Nb(2)-Nb(2) bond length is 2.95 Å. Both Nb(2)-Nb(1) bond lengths are 3.05 Å. The Nb(2)-Fe(1) bond length is 2.98 Å. Both Nb(2)-Fe(3) bond lengths are 2.90 Å. There are two shorter (2.87 Å) and two longer (2.88 Å) Nb(2)-Fe(2) bond lengths. Both Nb(2)-Al(2) bond lengths are 2.95 Å. There is one shorter (2.83 Å) and two longer (2.94 Å) Nb(2)-Al(1) bond lengths. In the third Nb site, Nb(1) is bonded in a 16-coordinate geometry to one Nb(1), three equivalent Nb(2), one Fe(3), two equivalent Fe(1), two equivalent Fe(2), three equivalent Al(1), and four equivalent Al(2) atoms. There is one shorter (3.00 Å) and two longer (3.05 Å) Nb(1)-Nb(2) bond lengths. The Nb(1)-Fe(3) bond length is 2.85 Å. Both Nb(1)-Fe(1) bond lengths are 2.96 Å. Both Nb(1)-Fe(2) bond lengths are 2.83 Å. There are two shorter (2.88 Å) and one longer (2.95 Å) Nb(1)-Al(1) bond length. There are two shorter (2.92 Å) and two longer (2.96 Å) Nb(1)-Al(2) bond lengths. In the fourth Nb site, Nb(1) is bonded in a 16-coordinate geometry to one Nb(1), three equivalent Nb(2), one Fe(3), two equivalent Fe(1), two equivalent Fe(2), three equivalent Al(1), and four equivalent Al(2) atoms. The Nb(1)-Nb(1) bond length is 3.20 Å. The Nb(1)-Fe(3) bond length is 2.85 Å. Both Nb(1)-Fe(1) bond lengths are 2.96 Å. Both Nb(1)-Fe(2) bond lengths are 2.83 Å. There are two shorter (2.88 Å) and one longer (2.95 Å) Nb(1)-Al(1) bond length. There are two shorter (2.92 Å) and two longer (2.96 Å) Nb(1)-Al(2) bond lengths. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Nb(2); four Nb(1,1); two equivalent Al(1); and four equivalent Al(2) atoms to form distorted FeNb6Al6 cuboctahedra that share corners with two equivalent Fe(3)Nb6Al2Fe4 cuboctahedra, corners with four equivalent Fe(1)Nb6Al6 cuboctahedra, corners with eight equivalent Fe(2)Nb6Al2Fe4 cuboctahedra, edges with two equivalent Fe(1)Nb6Al6 cuboctahedra, edges with four equivalent Fe(3)Nb6Al2Fe4 cuboctahedra, and faces with four equivalent Fe(2)Nb6Al2Fe4 cuboctahedra. Both Fe(1)-Al(1) bond lengths are 2.50 Å. There are two shorter (2.42 Å) and two longer (2.52 Å) Fe(1)-Al(2) bond lengths. In the second Fe site, Fe(2) is bonded to two Nb(1,1); four equivalent Nb(2); two equivalent Fe(2); two equivalent Fe(3); and two equivalent Al(1) atoms to form distorted FeNb6Al2Fe4 cuboctahedra that share corners with four equivalent Fe(2)Nb6Al2Fe4 cuboctahedra, corners with four equivalent Fe(1)Nb6Al6 cuboctahedra, edges with two equivalent Fe(2)Nb6Al2Fe4 cuboctahedra, faces with two equivalent Fe(1)Nb6Al6 cuboctahedra, faces with four equivalent Fe(2)Nb6Al2Fe4 cuboctahedra, and faces with four equivalent Fe(3)Nb6Al2Fe4 cuboctahedra. There is one shorter (2.40 Å) and one longer (2.59 Å) Fe(2)-Fe(2) bond length. There is one shorter (2.39 Å) and one longer (2.55 Å) Fe(2)-Fe(3) bond length. Both Fe(2)-Al(1) bond lengths are 2.46 Å. In the third Fe site, Fe(3) is bonded to two Nb(1,1); four equivalent Nb(2); four equivalent Fe(2); and two equivalent Al(1) atoms to form distorted FeNb6Al2Fe4 cuboctahedra that share corners with two equivalent Fe(1)Nb6Al6 cuboctahedra, corners with four equivalent Fe(3)Nb6Al2Fe4 cuboctahedra, edges with two equivalent Fe(3)Nb6Al2Fe4 cuboctahedra, edges with four equivalent Fe(1)Nb6Al6 cuboctahedra, and faces with eight equivalent Fe(2)Nb6Al2Fe4 cuboctahedra. Both Fe(3)-Al(1) bond lengths are 2.48 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 4-coordinate geometry to three Nb(1,1); three equivalent Nb(2); one Fe(1); one Fe(3); two equivalent Fe(2); and two equivalent Al(2) atoms. Both Al(1)-Al(2) bond lengths are 2.60 Å. In the second Al site, Al(2) is bonded in a 12-coordinate geometry to two equivalent Nb(2); four Nb(1,1,1); two equivalent Fe(1); two equivalent Al(1); and two equivalent Al(2) atoms. There is one shorter (2.43 Å) and one longer (2.56 Å) Al(2)-Al(2) bond length.