Materials Data on Nb4Co4Si7 by Materials Project

Abstract

Nb4Co4Si7 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Nb2+ sites. In the first Nb2+ site, Nb2+ is bonded to seven Si+1.71- atoms to form NbSi7 pentagonal bipyramids that share corners with eight equivalent CoSi6 octahedra, corners with eight NbSi7 pentagonal bipyramids, an edgeedge with one NbSi7 pentagonal bipyramid, faces with four equivalent CoSi6 octahedra, and faces with six NbSi7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 42–53°. There are a spread of Nb–Si bond distances ranging from 2.64–2.84 Å. In the second Nb2+ site, Nb2+ is bonded to seven Si+1.71- atoms to form NbSi7 pentagonal bipyramids that share corners with eight equivalent CoSi6 octahedra, corners with eight NbSi7 pentagonal bipyramids, edges with three equivalent NbSi7 pentagonal bipyramids, faces with four equivalent CoSi6 octahedra, and faces with six NbSi7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 43–51°. There are a spread of Nb–Si bond distances ranging from 2.66–2.84 Å. Co1+ is bonded to six Si+1.71- atoms to form distorted CoSi6 octahedra that share corners with six equivalent CoSi6 octahedra, corners with eight NbSi7 pentagonal bipyramids, edges with three equivalent CoSi6 octahedra, faces with two equivalent CoSi6 octahedra, and faces with four NbSi7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 34–37°. There are a spread of Co–Si bond distances ranging from 2.32–2.36 Å. There are four inequivalent Si+1.71- sites. In the first Si+1.71- site, Si+1.71- is bonded in a 9-coordinate geometry to five Nb2+ and four equivalent Co1+ atoms. In the second Si+1.71- site, Si+1.71- is bonded in a 6-coordinate geometry to one Nb2+, four equivalent Co1+, and one Si+1.71- atom. The Si–Si bond length is 2.38 Å. In the third Si+1.71- site, Si+1.71- is bonded in a 10-coordinate geometry to eight Nb2+ and two equivalent Si+1.71- atoms. There are one shorter (2.50 Å) and one longer (2.51 Å) Si–Si bond lengths. In the fourth Si+1.71- site, Si+1.71- is bonded in a 12-coordinate geometry to four Nb2+ and four equivalent Co1+ atoms.