Hf(Nb)Si crystallizes in the orthorhombic Amm2 space group. There are six inequivalent Hf sites. In the first Hf site, Hf(1) is bonded in a 16-coordinate geometry to one Hf(1); three Hf(2,2); three equivalent Nb(1); four equivalent Nb(2); one Si(3); two equivalent Si(1); and two equivalent Si(2) atoms. In the second Hf site, Hf(2) is bonded in a 16-coordinate geometry to one Hf(2); three Hf(1,1); two equivalent Nb(2); three equivalent Nb(1); one Si(1); two equivalent Si(3); and four equivalent Si(2) atoms. In the third Hf site, Hf(2) is bonded in a 16-coordinate geometry to one Hf(2), three equivalent Hf(1), two equivalent Nb(2), three equivalent Nb(1), one Si(1), two equivalent Si(3), and four equivalent Si(2) atoms. In the fourth Hf site, Hf(1) is bonded in a 16-coordinate geometry to one Hf(1); three Hf(2,2); three equivalent Nb(1); four equivalent Nb(2); one Si(3); two equivalent Si(1); and two equivalent Si(2) atoms. In the fifth Hf site, Hf(1) is bonded in a 16-coordinate geometry to one Hf(1); three Hf(2,2); three equivalent Nb(1); four equivalent Nb(2); one Si(3); two equivalent Si(1); and two equivalent Si(2) atoms. In the sixth Hf site, Hf(2) is bonded in a 16-coordinate geometry to one Hf(2); three Hf(1,1); two equivalent Nb(2); three equivalent Nb(1); one Si(1); two equivalent Si(3); and four equivalent Si(2) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 12-coordinate geometry to three Hf(1,1); three Hf(2,2); two equivalent Nb(2); one Si(1); one Si(3); and two equivalent Si(2) atoms. In the second Nb site, Nb(2) is bonded to two Hf(2,2); four Hf(1,1,1); two equivalent Nb(1); two equivalent Nb(2); and two equivalent Si(1) atoms to form distorted NbHf6Nb4Si2 cuboctahedra that share corners with four equivalent Nb(2)Hf6Nb4Si2 cuboctahedra, edges with two equivalent Nb(2)Hf6Nb4Si2 cuboctahedra, faces with four equivalent Nb(2)Hf6Nb4Si2 cuboctahedra, and faces with four equivalent Si(1)Hf6Nb6 cuboctahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to two Hf(2,2); four Hf(1,1); two equivalent Nb(1); and four equivalent Nb(2) atoms to form SiHf6Nb6 cuboctahedra that share corners with four equivalent Si(1)Hf6Nb6 cuboctahedra, edges with two equivalent Si(1)Hf6Nb6 cuboctahedra, and faces with eight equivalent Nb(2)Hf6Nb4Si2 cuboctahedra. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two Hf(1,1); four Hf(2,2,2); two equivalent Nb(1); one Si(2); and one Si(3) atom. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to two Hf(1,1); four Hf(2,2); two equivalent Nb(1); and two equivalent Si(2) atoms.
Hf(Nb)Si crystallizes in the orthorhombic Amm2 space group. There are six inequivalent Hf sites. In the first Hf site, Hf(1) is bonded in a 16-coordinate geometry to one Hf(1); three Hf(2,2); three equivalent Nb(1); four equivalent Nb(2); one Si(3); two equivalent Si(1); and two equivalent Si(2) atoms. The Hf(1)-Hf(1) bond length is 3.31 Å. There is one shorter (3.25 Å) and two longer (3.33 Å) Hf(1)-Hf(2,2) bond lengths. There is one shorter (3.19 Å) and two longer (3.24 Å) Hf(1)-Nb(1) bond lengths. There are two shorter (3.18 Å) and two longer (3.20 Å) Hf(1)-Nb(2) bond lengths. The Hf(1)-Si(3) bond length is 2.88 Å. Both Hf(1)-Si(1) bond lengths are 3.22 Å. Both Hf(1)-Si(2) bond lengths are 2.90 Å. In the second Hf site, Hf(2) is bonded in a 16-coordinate geometry to one Hf(2); three Hf(1,1); two equivalent Nb(2); three equivalent Nb(1); one Si(1); two equivalent Si(3); and four equivalent Si(2) atoms. The Hf(2)-Hf(2) bond length is 3.15 Å. Both Hf(2)-Hf(1) bond lengths are 3.33 Å. Both Hf(2)-Nb(2) bond lengths are 3.04 Å. There are two shorter (3.17 Å) and one longer (3.18 Å) Hf(2)-Nb(1) bond length. The Hf(2)-Si(1) bond length is 3.07 Å. Both Hf(2)-Si(3) bond lengths are 3.19 Å. There are two shorter (3.11 Å) and two longer (3.19 Å) Hf(2)-Si(2) bond lengths. In the third Hf site, Hf(2) is bonded in a 16-coordinate geometry to one Hf(2), three equivalent Hf(1), two equivalent Nb(2), three equivalent Nb(1), one Si(1), two equivalent Si(3), and four equivalent Si(2) atoms. There is one shorter (3.25 Å) and two longer (3.33 Å) Hf(2)-Hf(1) bond lengths. Both Hf(2)-Nb(2) bond lengths are 3.04 Å. There are two shorter (3.17 Å) and one longer (3.18 Å) Hf(2)-Nb(1) bond length. The Hf(2)-Si(1) bond length is 3.07 Å. Both Hf(2)-Si(3) bond lengths are 3.19 Å. There are two shorter (3.11 Å) and two longer (3.19 Å) Hf(2)-Si(2) bond lengths. In the fourth Hf site, Hf(1) is bonded in a 16-coordinate geometry to one Hf(1); three Hf(2,2); three equivalent Nb(1); four equivalent Nb(2); one Si(3); two equivalent Si(1); and two equivalent Si(2) atoms. Both Hf(1)-Hf(2) bond lengths are 3.33 Å. There is one shorter (3.19 Å) and two longer (3.24 Å) Hf(1)-Nb(1) bond lengths. There are two shorter (3.18 Å) and two longer (3.20 Å) Hf(1)-Nb(2) bond lengths. The Hf(1)-Si(3) bond length is 2.88 Å. Both Hf(1)-Si(1) bond lengths are 3.22 Å. Both Hf(1)-Si(2) bond lengths are 2.90 Å. In the fifth Hf site, Hf(1) is bonded in a 16-coordinate geometry to one Hf(1); three Hf(2,2); three equivalent Nb(1); four equivalent Nb(2); one Si(3); two equivalent Si(1); and two equivalent Si(2) atoms. The Hf(1)-Hf(1) bond length is 3.31 Å. The Hf(1)-Hf(2) bond length is 3.25 Å. There is one shorter (3.19 Å) and two longer (3.24 Å) Hf(1)-Nb(1) bond lengths. There are two shorter (3.18 Å) and two longer (3.20 Å) Hf(1)-Nb(2) bond lengths. The Hf(1)-Si(3) bond length is 2.88 Å. Both Hf(1)-Si(1) bond lengths are 3.22 Å. Both Hf(1)-Si(2) bond lengths are 2.90 Å. In the sixth Hf site, Hf(2) is bonded in a 16-coordinate geometry to one Hf(2); three Hf(1,1); two equivalent Nb(2); three equivalent Nb(1); one Si(1); two equivalent Si(3); and four equivalent Si(2) atoms. The Hf(2)-Hf(2) bond length is 3.15 Å. Both Hf(2)-Nb(2) bond lengths are 3.04 Å. There are two shorter (3.17 Å) and one longer (3.18 Å) Hf(2)-Nb(1) bond length. The Hf(2)-Si(1) bond length is 3.07 Å. Both Hf(2)-Si(3) bond lengths are 3.19 Å. There are two shorter (3.11 Å) and two longer (3.19 Å) Hf(2)-Si(2) bond lengths. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 12-coordinate geometry to three Hf(1,1); three Hf(2,2); two equivalent Nb(2); one Si(1); one Si(3); and two equivalent Si(2) atoms. Both Nb(1)-Nb(2) bond lengths are 2.80 Å. The Nb(1)-Si(1) bond length is 2.78 Å. The Nb(1)-Si(3) bond length is 2.58 Å. Both Nb(1)-Si(2) bond lengths are 2.59 Å. In the second Nb site, Nb(2) is bonded to two Hf(2,2); four Hf(1,1,1); two equivalent Nb(1); two equivalent Nb(2); and two equivalent Si(1) atoms to form distorted NbHf6Nb4Si2 cuboctahedra that share corners with four equivalent Nb(2)Hf6Nb4Si2 cuboctahedra, edges with two equivalent Nb(2)Hf6Nb4Si2 cuboctahedra, faces with four equivalent Nb(2)Hf6Nb4Si2 cuboctahedra, and faces with four equivalent Si(1)Hf6Nb6 cuboctahedra. There is one shorter (2.73 Å) and one longer (2.79 Å) Nb(2)-Nb(2) bond length. There is one shorter (2.71 Å) and one longer (2.74 Å) Nb(2)-Si(1) bond length. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to two Hf(2,2); four Hf(1,1); two equivalent Nb(1); and four equivalent Nb(2) atoms to form SiHf6Nb6 cuboctahedra that share corners with four equivalent Si(1)Hf6Nb6 cuboctahedra, edges with two equivalent Si(1)Hf6Nb6 cuboctahedra, and faces with eight equivalent Nb(2)Hf6Nb4Si2 cuboctahedra. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two Hf(1,1); four Hf(2,2,2); two equivalent Nb(1); one Si(2); and one Si(3) atom. The Si(2)-Si(2) bond length is 2.44 Å. The Si(2)-Si(3) bond length is 2.42 Å. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to two Hf(1,1); four Hf(2,2); two equivalent Nb(1); and two equivalent Si(2) atoms.