Nb3Ni8Si crystallizes in the trigonal P3m1 space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 16-coordinate geometry to one Nb(2), three equivalent Ni(1), three equivalent Ni(3), six equivalent Ni(4), and three equivalent Si(1) atoms. In the second Nb site, Nb(2) is bonded in a 16-coordinate geometry to one Nb(1), three equivalent Nb(3), three equivalent Ni(2), three equivalent Ni(3), and six equivalent Ni(4) atoms. In the third Nb site, Nb(3) is bonded in a 16-coordinate geometry to three equivalent Nb(2), three equivalent Ni(2), three equivalent Ni(4), six equivalent Ni(3), and one Si(1) atom. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to three equivalent Nb(1), three equivalent Ni(3), three equivalent Ni(4), and three equivalent Si(1) atoms to form NiNb3Si3Ni6 cuboctahedra that share corners with six equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, corners with six equivalent Ni(4)Nb5SiNi6 cuboctahedra, edges with six equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, faces with two equivalent Ni(2)Nb6Ni6 cuboctahedra, faces with nine equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, and faces with nine equivalent Ni(4)Nb5SiNi6 cuboctahedra. In the second Ni site, Ni(2) is bonded to three equivalent Nb(2), three equivalent Nb(3), three equivalent Ni(3), and three equivalent Ni(4) atoms to form NiNb6Ni6 cuboctahedra that share corners with six equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, corners with six equivalent Ni(4)Nb5SiNi6 cuboctahedra, edges with six equivalent Ni(2)Nb6Ni6 cuboctahedra, faces with two equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, faces with nine equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, and faces with nine equivalent Ni(4)Nb5SiNi6 cuboctahedra. In the third Ni site, Ni(3) is bonded to one Nb(1), one Nb(2), two equivalent Nb(3), one Ni(1), one Ni(2), four equivalent Ni(3), and two equivalent Si(1) atoms to form distorted NiNb4Si2Ni6 cuboctahedra that share corners with two equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, corners with two equivalent Ni(2)Nb6Ni6 cuboctahedra, corners with four equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, corners with ten equivalent Ni(4)Nb5SiNi6 cuboctahedra, edges with two equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, edges with four equivalent Ni(4)Nb5SiNi6 cuboctahedra, faces with three equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, faces with three equivalent Ni(2)Nb6Ni6 cuboctahedra, faces with four equivalent Ni(4)Nb5SiNi6 cuboctahedra, and faces with eight equivalent Ni(3)Nb4Si2Ni6 cuboctahedra. In the fourth Ni site, Ni(4) is bonded to one Nb(3), two equivalent Nb(1), two equivalent Nb(2), one Ni(1), one Ni(2), four equivalent Ni(4), and one Si(1) atom to form NiNb5SiNi6 cuboctahedra that share corners with two equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, corners with two equivalent Ni(2)Nb6Ni6 cuboctahedra, corners with four equivalent Ni(4)Nb5SiNi6 cuboctahedra, corners with ten equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, edges with two equivalent Ni(4)Nb5SiNi6 cuboctahedra, edges with four equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, faces with three equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, faces with three equivalent Ni(2)Nb6Ni6 cuboctahedra, faces with four equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, and faces with eight equivalent Ni(4)Nb5SiNi6 cuboctahedra. Si(1) is bonded in a 16-coordinate geometry to one Nb(3), three equivalent Nb(1), three equivalent Ni(1), three equivalent Ni(4), and six equivalent Ni(3) atoms.
Nb3Ni8Si crystallizes in the trigonal P3m1 space group. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 16-coordinate geometry to one Nb(2), three equivalent Ni(1), three equivalent Ni(3), six equivalent Ni(4), and three equivalent Si(1) atoms. The Nb(1)-Nb(2) bond length is 2.94 Å. All Nb(1)-Ni(1) bond lengths are 2.81 Å. All Nb(1)-Ni(3) bond lengths are 2.73 Å. All Nb(1)-Ni(4) bond lengths are 2.81 Å. All Nb(1)-Si(1) bond lengths are 2.88 Å. In the second Nb site, Nb(2) is bonded in a 16-coordinate geometry to one Nb(1), three equivalent Nb(3), three equivalent Ni(2), three equivalent Ni(3), and six equivalent Ni(4) atoms. All Nb(2)-Nb(3) bond lengths are 2.97 Å. All Nb(2)-Ni(2) bond lengths are 2.80 Å. All Nb(2)-Ni(3) bond lengths are 2.75 Å. All Nb(2)-Ni(4) bond lengths are 2.82 Å. In the third Nb site, Nb(3) is bonded in a 16-coordinate geometry to three equivalent Nb(2), three equivalent Ni(2), three equivalent Ni(4), six equivalent Ni(3), and one Si(1) atom. All Nb(3)-Ni(2) bond lengths are 2.84 Å. All Nb(3)-Ni(4) bond lengths are 2.90 Å. All Nb(3)-Ni(3) bond lengths are 2.73 Å. The Nb(3)-Si(1) bond length is 2.88 Å. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to three equivalent Nb(1), three equivalent Ni(3), three equivalent Ni(4), and three equivalent Si(1) atoms to form NiNb3Si3Ni6 cuboctahedra that share corners with six equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, corners with six equivalent Ni(4)Nb5SiNi6 cuboctahedra, edges with six equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, faces with two equivalent Ni(2)Nb6Ni6 cuboctahedra, faces with nine equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, and faces with nine equivalent Ni(4)Nb5SiNi6 cuboctahedra. All Ni(1)-Ni(3) bond lengths are 2.37 Å. All Ni(1)-Ni(4) bond lengths are 2.38 Å. All Ni(1)-Si(1) bond lengths are 2.79 Å. In the second Ni site, Ni(2) is bonded to three equivalent Nb(2), three equivalent Nb(3), three equivalent Ni(3), and three equivalent Ni(4) atoms to form NiNb6Ni6 cuboctahedra that share corners with six equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, corners with six equivalent Ni(4)Nb5SiNi6 cuboctahedra, edges with six equivalent Ni(2)Nb6Ni6 cuboctahedra, faces with two equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, faces with nine equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, and faces with nine equivalent Ni(4)Nb5SiNi6 cuboctahedra. All Ni(2)-Ni(3) bond lengths are 2.41 Å. All Ni(2)-Ni(4) bond lengths are 2.37 Å. In the third Ni site, Ni(3) is bonded to one Nb(1), one Nb(2), two equivalent Nb(3), one Ni(1), one Ni(2), four equivalent Ni(3), and two equivalent Si(1) atoms to form distorted NiNb4Si2Ni6 cuboctahedra that share corners with two equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, corners with two equivalent Ni(2)Nb6Ni6 cuboctahedra, corners with four equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, corners with ten equivalent Ni(4)Nb5SiNi6 cuboctahedra, edges with two equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, edges with four equivalent Ni(4)Nb5SiNi6 cuboctahedra, faces with three equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, faces with three equivalent Ni(2)Nb6Ni6 cuboctahedra, faces with four equivalent Ni(4)Nb5SiNi6 cuboctahedra, and faces with eight equivalent Ni(3)Nb4Si2Ni6 cuboctahedra. There are two shorter (2.36 Å) and two longer (2.43 Å) Ni(3)-Ni(3) bond lengths. Both Ni(3)-Si(1) bond lengths are 2.87 Å. In the fourth Ni site, Ni(4) is bonded to one Nb(3), two equivalent Nb(1), two equivalent Nb(2), one Ni(1), one Ni(2), four equivalent Ni(4), and one Si(1) atom to form NiNb5SiNi6 cuboctahedra that share corners with two equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, corners with two equivalent Ni(2)Nb6Ni6 cuboctahedra, corners with four equivalent Ni(4)Nb5SiNi6 cuboctahedra, corners with ten equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, edges with two equivalent Ni(4)Nb5SiNi6 cuboctahedra, edges with four equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, faces with three equivalent Ni(1)Nb3Si3Ni6 cuboctahedra, faces with three equivalent Ni(2)Nb6Ni6 cuboctahedra, faces with four equivalent Ni(3)Nb4Si2Ni6 cuboctahedra, and faces with eight equivalent Ni(4)Nb5SiNi6 cuboctahedra. There are two shorter (2.36 Å) and two longer (2.44 Å) Ni(4)-Ni(4) bond lengths. The Ni(4)-Si(1) bond length is 2.64 Å. Si(1) is bonded in a 16-coordinate geometry to one Nb(3), three equivalent Nb(1), three equivalent Ni(1), three equivalent Ni(4), and six equivalent Ni(3) atoms.