DOI: 10.17188/1726829
title: Materials Data on Nb3(CrSi)8 by Materials Project

description: Nb3(CrSi)8 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are three inequivalent Nb2+ sites. In the first Nb2+ site, Nb2+ is bonded to seven Si3- atoms to form NbSi7 pentagonal bipyramids that share corners with seven NbSi7 pentagonal bipyramids, corners with two equivalent CrSi6 pentagonal pyramids, an edgeedge with one NbSi7 pentagonal bipyramid, edges with two equivalent CrSi6 pentagonal pyramids, and faces with two equivalent CrSi6 pentagonal pyramids. There are a spread of Nb–Si bond distances ranging from 2.57–2.68 Å. In the second Nb2+ site, Nb2+ is bonded to seven Si3- atoms to form NbSi7 pentagonal bipyramids that share corners with four NbSi7 pentagonal bipyramids, corners with four CrSi6 pentagonal pyramids, edges with three NbSi7 pentagonal bipyramids, faces with two equivalent NbSi7 pentagonal bipyramids, and faces with two equivalent CrSi6 pentagonal pyramids. There are a spread of Nb–Si bond distances ranging from 2.52–2.68 Å. In the third Nb2+ site, Nb2+ is bonded to seven Si3- atoms to form NbSi7 pentagonal bipyramids that share corners with seven NbSi7 pentagonal bipyramids, edges with three equivalent CrSi6 pentagonal pyramids, faces with two equivalent NbSi7 pentagonal bipyramids, and a faceface with one CrSi6 pentagonal pyramid. There are a spread of Nb–Si bond distances ranging from 2.64–2.74 Å. There are six inequivalent Cr+2.25+ sites. In the first Cr+2.25+ site, Cr+2.25+ is bonded in a 7-coordinate geometry to one Cr+2.25+ and six Si3- atoms. The Cr–Cr bond length is 2.56 Å. There are a spread of Cr–Si bond distances ranging from 2.37–2.75 Å. In the second Cr+2.25+ site, Cr+2.25+ is bonded in a 7-coordinate geometry to one Cr+2.25+ and six Si3- atoms. There are a spread of Cr–Si bond distances ranging from 2.45–2.72 Å. In the third Cr+2.25+ site, Cr+2.25+ is bonded to six Si3- atoms to form CrSi6 pentagonal pyramids that share corners with three equivalent NbSi7 pentagonal bipyramids, corners with three CrSi6 pentagonal pyramids, edges with three equivalent NbSi7 pentagonal bipyramids, an edgeedge with one CrSi6 pentagonal pyramid, and faces with two equivalent NbSi7 pentagonal bipyramids. There are a spread of Cr–Si bond distances ranging from 2.36–2.58 Å. In the fourth Cr+2.25+ site, Cr+2.25+ is bonded in a 7-coordinate geometry to two equivalent Cr+2.25+ and five Si3- atoms. There are one shorter (2.33 Å) and one longer (2.49 Å) Cr–Cr bond lengths. There are a spread of Cr–Si bond distances ranging from 2.43–2.48 Å. In the fifth Cr+2.25+ site, Cr+2.25+ is bonded in a 8-coordinate geometry to two equivalent Cr+2.25+ and six Si3- atoms. There are one shorter (2.32 Å) and one longer (2.50 Å) Cr–Cr bond lengths. There are a spread of Cr–Si bond distances ranging from 2.50–2.57 Å. In the sixth Cr+2.25+ site, Cr+2.25+ is bonded to six Si3- atoms to form CrSi6 pentagonal pyramids that share corners with three NbSi7 pentagonal bipyramids, corners with three CrSi6 pentagonal pyramids, edges with two equivalent NbSi7 pentagonal bipyramids, an edgeedge with one CrSi6 pentagonal pyramid, and faces with three NbSi7 pentagonal bipyramids. There are a spread of Cr–Si bond distances ranging from 2.38–2.58 Å. There are seven inequivalent Si3- sites. In the first Si3- site, Si3- is bonded in a 10-coordinate geometry to two Nb2+ and eight Cr+2.25+ atoms. In the second Si3- site, Si3- is bonded in a 9-coordinate geometry to three Nb2+ and six Cr+2.25+ atoms. In the third Si3- site, Si3- is bonded in a 9-coordinate geometry to two equivalent Nb2+ and seven Cr+2.25+ atoms. In the fourth Si3- site, Si3- is bonded in a 9-coordinate geometry to three Nb2+, four Cr+2.25+, and two equivalent Si3- atoms. There are one shorter (2.41 Å) and one longer (2.42 Å) Si–Si bond lengths. In the fifth Si3- site, Si3- is bonded in a 9-coordinate geometry to four Nb2+ and five Cr+2.25+ atoms. In the sixth Si3- site, Si3- is bonded in a 8-coordinate geometry to two Nb2+ and six Cr+2.25+ atoms. In the seventh Si3- site, Si3- is bonded in a 8-coordinate geometry to two Nb2+ and six Cr+2.25+ atoms.