Materials Data on Nb4FeS8 by Materials Project
Nb4FeS8 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two Nb4FeS8 sheets oriented in the (1, 0, 0) direction. there are two inequivalent Nb+3.50+ sites. In the first Nb+3.50+ site, Nb+3.50+ is bonded to six S2- atoms to form distorted NbS6 pentagonal pyramids that share corners with four equivalent FeS6 octahedra and edges with six NbS6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 48–49°. There are a spread of Nb–S bond distances ranging from 2.49–2.53 Å. In the second Nb+3.50+ site, Nb+3.50+ is bonded to six S2- atoms to form distorted NbS6 pentagonal pyramids that share corners with two equivalent FeS6 octahedra, edges with six NbS6 pentagonal pyramids, and a faceface with one FeS6 octahedra. The corner-sharing octahedral tilt angles are 47°. There are a spread of Nb–S bond distances ranging from 2.45–2.53 Å. Fe2+ is bonded to six S2- atoms to form FeS6 octahedra that share corners with twelve NbS6 pentagonal pyramids, edges with two equivalent FeS6 octahedra, and faces with two equivalent NbS6 pentagonal pyramids. There are two shorter (2.28 Å) and four longer (2.31 Å) Fe–S bond lengths. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.50+ atoms. In the second S2- site, S2- is bonded in a 3-coordinate geometry to three Nb+3.50+ atoms. In the third S2- site, S2- is bonded in a 5-coordinate geometry to three Nb+3.50+ and two equivalent Fe2+ atoms. In the fourth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three Nb+3.50+ and one Fe2+ atom.