Nb4Co4Si7 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 7-coordinate geometry to four equivalent Co(1), one Si(2), two equivalent Si(1), two equivalent Si(3), and two equivalent Si(4) atoms. In the second Nb site, Nb(2) is bonded in a 7-coordinate geometry to four equivalent Co(1), two equivalent Si(3), two equivalent Si(4), and three equivalent Si(1) atoms. Co(1) is bonded to two equivalent Nb(1), two equivalent Nb(2), two equivalent Co(1), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(4) atoms to form a mixture of distorted edge, face, and corner-sharing CoNb4Co2Si6 cuboctahedra. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Nb(1), three equivalent Nb(2), and four equivalent Co(1) atoms. In the second Si site, Si(2) is bonded in a 6-coordinate geometry to one Nb(1), four equivalent Co(1), and one Si(2) atom. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to four equivalent Nb(1), four equivalent Nb(2), and two equivalent Si(3) atoms. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to two equivalent Nb(1), two equivalent Nb(2), and four equivalent Co(1) atoms.
Nb4Co4Si7 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 7-coordinate geometry to four equivalent Co(1), one Si(2), two equivalent Si(1), two equivalent Si(3), and two equivalent Si(4) atoms. All Nb(1)-Co(1) bond lengths are 3.00 Å. The Nb(1)-Si(2) bond length is 2.67 Å. Both Nb(1)-Si(1) bond lengths are 2.63 Å. Both Nb(1)-Si(3) bond lengths are 2.70 Å. Both Nb(1)-Si(4) bond lengths are 2.82 Å. In the second Nb site, Nb(2) is bonded in a 7-coordinate geometry to four equivalent Co(1), two equivalent Si(3), two equivalent Si(4), and three equivalent Si(1) atoms. All Nb(2)-Co(1) bond lengths are 2.99 Å. Both Nb(2)-Si(3) bond lengths are 2.68 Å. Both Nb(2)-Si(4) bond lengths are 2.67 Å. There is one shorter (2.77 Å) and two longer (2.81 Å) Nb(2)-Si(1) bond lengths. Co(1) is bonded to two equivalent Nb(1), two equivalent Nb(2), two equivalent Co(1), two equivalent Si(1), two equivalent Si(2), and two equivalent Si(4) atoms to form a mixture of distorted edge, face, and corner-sharing CoNb4Co2Si6 cuboctahedra. Both Co(1)-Co(1) bond lengths are 2.48 Å. Both Co(1)-Si(1) bond lengths are 2.30 Å. Both Co(1)-Si(2) bond lengths are 2.33 Å. Both Co(1)-Si(4) bond lengths are 2.33 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Nb(1), three equivalent Nb(2), and four equivalent Co(1) atoms. In the second Si site, Si(2) is bonded in a 6-coordinate geometry to one Nb(1), four equivalent Co(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.36 Å. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to four equivalent Nb(1), four equivalent Nb(2), and two equivalent Si(3) atoms. There is one shorter (2.47 Å) and one longer (2.48 Å) Si(3)-Si(3) bond length. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to two equivalent Nb(1), two equivalent Nb(2), and four equivalent Co(1) atoms.