Materials Data on Nb4CuSe8 by Materials Project
Nb4CuSe8 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one Nb4CuSe8 sheet oriented in the (0, 0, 1) direction. there are two inequivalent Nb+3.75+ sites. In the first Nb+3.75+ site, Nb+3.75+ is bonded to six Se2- atoms to form distorted NbSe6 pentagonal pyramids that share corners with four equivalent CuSe6 octahedra and edges with six NbSe6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 45–48°. There are a spread of Nb–Se bond distances ranging from 2.61–2.65 Å. In the second Nb+3.75+ site, Nb+3.75+ is bonded to six Se2- atoms to form distorted NbSe6 pentagonal pyramids that share corners with two equivalent CuSe6 octahedra, edges with six NbSe6 pentagonal pyramids, and a faceface with one CuSe6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Nb–Se bond distances ranging from 2.60–2.66 Å. Cu1+ is bonded to six Se2- atoms to form CuSe6 octahedra that share corners with twelve NbSe6 pentagonal pyramids, edges with two equivalent CuSe6 octahedra, and faces with two equivalent NbSe6 pentagonal pyramids. There are a spread of Cu–Se bond distances ranging from 2.58–2.61 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three Nb+3.75+ and one Cu1+ atom to form distorted corner-sharing SeNb3Cu trigonal pyramids. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to three Nb+3.75+ and two equivalent Cu1+ atoms. In the third Se2- site, Se2- is bonded in a distorted T-shaped geometry to three Nb+3.75+ atoms. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Nb+3.75+ atoms.