Nb5Si3 crystallizes in the tetragonal I4/mcm space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 5-coordinate geometry to two equivalent Si(2) and three equivalent Si(1) atoms. In the second Nb site, Nb(2) is bonded to two equivalent Si(2) and four equivalent Si(1) atoms to form distorted corner-sharing NbSi6 octahedra. The corner-sharing octahedral tilt angles range from 0-52°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Nb(2), six equivalent Nb(1), and one Si(1) atom. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Nb(2) and eight equivalent Nb(1) atoms.
Nb5Si3 crystallizes in the tetragonal I4/mcm space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 5-coordinate geometry to two equivalent Si(2) and three equivalent Si(1) atoms. Both Nb(1)-Si(2) bond lengths are 2.74 Å. There is one shorter (2.61 Å) and two longer (2.65 Å) Nb(1)-Si(1) bond lengths. In the second Nb site, Nb(2) is bonded to two equivalent Si(2) and four equivalent Si(1) atoms to form distorted corner-sharing NbSi6 octahedra. The corner-sharing octahedral tilt angles range from 0-52°. Both Nb(2)-Si(2) bond lengths are 2.98 Å. All Nb(2)-Si(1) bond lengths are 2.60 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Nb(2), six equivalent Nb(1), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.40 Å. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Nb(2) and eight equivalent Nb(1) atoms.