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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Nb2Cr4Si5 by Materials Project

Nb2Cr4Si5 crystallizes in the orthorhombic Ibam space group. The structure is three-dimensional. Nb2+ is bonded to seven Si+2.40- atoms to form a mixture of corner, edge, and face-sharing NbSi7 pentagonal bipyramids. There are a spread of Nb–Si bond distances ranging from 2.57–2.75 Å. There are two inequivalent Cr2+ sites. In the first Cr2+ site, Cr2+ is bonded in a 8-coordinate geometry to two equivalent Cr2+ and six Si+2.40- atoms. Both Cr–Cr bond lengths are 2.43 Å. There are a spread of Cr–Si bond distances ranging from 2.42–2.53 Å. In the second Cr2+ site, Cr2+ is bonded in a 7-coordinate geometry to seven Si+2.40- atoms. There are a spread of Cr–Si bond distances ranging from 2.35–2.74 Å. There are three inequivalent Si+2.40- sites. In the first Si+2.40- site, Si+2.40- is bonded in a 10-coordinate geometry to four equivalent Nb2+, four equivalent Cr2+, and two equivalent Si+2.40- atoms. Both Si–Si bond lengths are 2.43 Å. In the second Si+2.40- site, Si+2.40- is bonded in a 10-coordinate geometry to one Nb2+, six Cr2+, and three equivalent Si+2.40- atoms. There are one shorter (2.35 Å) and two longer (2.69 Å) Si–Si bond lengths. In the third Si+2.40- site, Si+2.40- is bonded in a 9-coordinate geometry to four equivalent Nb2+ and five Cr2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Materials Data on Nb2Cr4Si5 by Materials Project

Nb2Cr4Si5 crystallizes in the orthorhombic Ibam space group. The structure is three-dimensional. Nb2+ is bonded to six Si+2.40- atoms to form distorted NbSi6 octahedra that share corners with four equivalent NbSi6 octahedra, corners with six equivalent CrSi7 pentagonal bipyramids, edges with two equivalent NbSi6 octahedra, faces with two equivalent NbSi6 octahedra, and faces with four equivalent CrSi7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 40°. There are a spread of Nb–Si bond distances ranging from 2.58–2.64 Å. There are two inequivalent Cr2+ sites. In the first Cr2+ site, Cr2+ is bonded in a 7-coordinate geometry to seven Si+2.40- atoms. There are a spread of Cr–Si bond distances ranging from 2.29–2.82 Å. In the second Cr2+ site, Cr2+ is bonded to seven Si+2.40- atoms to form distorted CrSi7 pentagonal bipyramids that share corners with six equivalent NbSi6 octahedra, corners with six equivalent CrSi7 pentagonal bipyramids, edges with three equivalent CrSi7 pentagonal bipyramids, faces with four equivalent NbSi6 octahedra, and faces with two equivalent CrSi7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 40–54°. There are a spread of Cr–Si bond distances ranging from 2.52–2.93 Å. There are three inequivalent Si+2.40- sites. In the first Si+2.40- site, Si+2.40- is bonded in a 8-coordinate geometry to two equivalent Nb2+, five Cr2+, and one Si+2.40- atom. The Si–Si bond length is 2.37 Å. In the second Si+2.40- site, Si+2.40- is bonded in a 9-coordinate geometry to four equivalent Nb2+ and five Cr2+ atoms. In the third Si+2.40- site, Si+2.40- is bonded in a 10-coordinate geometry to eight Cr2+ and two equivalent Si+2.40- atoms. Both Si–Si bond lengths are 2.56 Å.

36 MATERIALS SCIENCE↗