Materials Data on Nb21S8 by Materials Project
Nb21S8 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. there are six inequivalent Nb sites. In the first Nb site, Nb is bonded in a 3-coordinate geometry to three S atoms. There are one shorter (2.50 Å) and two longer (2.59 Å) Nb–S bond lengths. In the second Nb site, Nb is bonded in an L-shaped geometry to two equivalent S atoms. Both Nb–S bond lengths are 2.50 Å. In the third Nb site, Nb is bonded in a 4-coordinate geometry to four S atoms. There are a spread of Nb–S bond distances ranging from 2.45–2.84 Å. In the fourth Nb site, Nb is bonded in a distorted rectangular see-saw-like geometry to four equivalent S atoms. There are two shorter (2.55 Å) and two longer (2.56 Å) Nb–S bond lengths. In the fifth Nb site, Nb is bonded in a distorted single-bond geometry to one S atom. The Nb–S bond length is 2.66 Å. In the sixth Nb site, Nb is bonded in a square co-planar geometry to four equivalent S atoms. All Nb–S bond lengths are 2.57 Å. There are two inequivalent S sites. In the first S site, S is bonded in a 8-coordinate geometry to eight Nb atoms. In the second S site, S is bonded in a 7-coordinate geometry to seven Nb atoms.