Materials Data on Nb4GeSe8 by Materials Project

Abstract

Nb4GeSe8 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two Nb4GeSe8 sheets oriented in the (1, 0, 0) direction. there are two inequivalent Nb3+ sites. In the first Nb3+ site, Nb3+ is bonded to six Se2- atoms to form distorted NbSe6 pentagonal pyramids that share corners with four equivalent GeSe6 octahedra and edges with six NbSe6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 44–45°. There are a spread of Nb–Se bond distances ranging from 2.62–2.65 Å. In the second Nb3+ site, Nb3+ is bonded to six Se2- atoms to form distorted NbSe6 pentagonal pyramids that share corners with two equivalent GeSe6 octahedra, edges with six NbSe6 pentagonal pyramids, and a faceface with one GeSe6 octahedra. The corner-sharing octahedral tilt angles are 46°. There are a spread of Nb–Se bond distances ranging from 2.59–2.66 Å. Ge4+ is bonded to six Se2- atoms to form distorted GeSe6 octahedra that share corners with twelve NbSe6 pentagonal pyramids, edges with two equivalent GeSe6 octahedra, and faces with two equivalent NbSe6 pentagonal pyramids. There are two shorter (2.78 Å) and four longer (2.81 Å) Ge–Se bond lengths. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three Nb3+ and one Ge4+ atom to form distorted corner-sharing SeNb3Ge trigonal pyramids. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to three Nb3+ and two equivalent Ge4+ atoms. In the third Se2- site, Se2- is bonded in a distorted T-shaped geometry to three Nb3+ atoms. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Nb3+ atoms.