Materials Data on Nb4FeSe8 by Materials Project
Nb4FeSe8 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Nb+3.50+ sites. In the first Nb+3.50+ site, Nb+3.50+ is bonded to six equivalent Se2- atoms to form distorted NbSe6 pentagonal pyramids that share edges with six equivalent NbSe6 pentagonal pyramids and faces with two equivalent FeSe6 octahedra. All Nb–Se bond lengths are 2.64 Å. In the second Nb+3.50+ site, Nb+3.50+ is bonded to six Se2- atoms to form distorted NbSe6 pentagonal pyramids that share corners with four equivalent FeSe6 octahedra and edges with six NbSe6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 48°. There are two shorter (2.59 Å) and four longer (2.64 Å) Nb–Se bond lengths. Fe2+ is bonded to six equivalent Se2- atoms to form FeSe6 octahedra that share corners with twelve equivalent NbSe6 pentagonal pyramids and faces with two equivalent NbSe6 pentagonal pyramids. All Fe–Se bond lengths are 2.57 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Nb+3.50+ atoms. In the second Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to three Nb+3.50+ and one Fe2+ atom.