DOI: 10.17188/1308429
title: Materials Data on Li2Fe4OF8 by Materials Project

description: Li2Fe4OF8 is Ilmenite-derived structured and crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to six F1- atoms to form LiF6 octahedra that share corners with six FeOF5 octahedra, corners with three equivalent FeOF5 pentagonal pyramids, and edges with three equivalent FeF6 octahedra. The corner-sharing octahedra tilt angles range from 45–65°. There are a spread of Li–F bond distances ranging from 2.04–2.17 Å. In the second Li1+ site, Li1+ is bonded in a 6-coordinate geometry to one O2- and five F1- atoms. The Li–O bond length is 2.01 Å. There are a spread of Li–F bond distances ranging from 1.99–2.45 Å. There are four inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to one O2- and five F1- atoms to form FeOF5 octahedra that share corners with three equivalent LiF6 octahedra, corners with three equivalent FeF6 octahedra, corners with three equivalent FeOF5 pentagonal pyramids, and a faceface with one FeOF5 octahedra. The corner-sharing octahedra tilt angles range from 45–65°. The Fe–O bond length is 2.02 Å. There are a spread of Fe–F bond distances ranging from 2.08–2.30 Å. In the second Fe2+ site, Fe2+ is bonded to one O2- and five F1- atoms to form FeOF5 octahedra that share corners with three equivalent LiF6 octahedra, corners with three equivalent FeF6 octahedra, edges with three equivalent FeOF5 pentagonal pyramids, and a faceface with one FeOF5 octahedra. The corner-sharing octahedra tilt angles range from 44–65°. The Fe–O bond length is 2.02 Å. There are a spread of Fe–F bond distances ranging from 2.07–2.33 Å. In the third Fe2+ site, Fe2+ is bonded to six F1- atoms to form FeF6 octahedra that share corners with six FeOF5 octahedra, edges with three equivalent LiF6 octahedra, and a faceface with one FeOF5 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 44–65°. There are a spread of Fe–F bond distances ranging from 2.04–2.21 Å. In the fourth Fe2+ site, Fe2+ is bonded to one O2- and five F1- atoms to form distorted FeOF5 pentagonal pyramids that share corners with three equivalent LiF6 octahedra, corners with three equivalent FeOF5 octahedra, edges with three equivalent FeOF5 octahedra, and a faceface with one FeF6 octahedra. The corner-sharing octahedra tilt angles range from 43–52°. The Fe–O bond length is 1.96 Å. There are a spread of Fe–F bond distances ranging from 2.07–2.35 Å. O2- is bonded to one Li1+ and three Fe2+ atoms to form distorted OLiFe3 trigonal pyramids that share edges with two FLi2Fe2 trigonal pyramids. There are eight inequivalent F1- sites. In the first F1- site, F1- is bonded in a 4-coordinate geometry to two Li1+ and two Fe2+ atoms. In the second F1- site, F1- is bonded in a 4-coordinate geometry to one Li1+ and three Fe2+ atoms. In the third F1- site, F1- is bonded in a rectangular see-saw-like geometry to one Li1+ and three Fe2+ atoms. In the fourth F1- site, F1- is bonded in a distorted see-saw-like geometry to two Li1+ and two Fe2+ atoms. In the fifth F1- site, F1- is bonded to one Li1+ and three Fe2+ atoms to form distorted FLiFe3 trigonal pyramids that share an edgeedge with one OLiFe3 trigonal pyramid and an edgeedge with one FLi2Fe2 trigonal pyramid. In the sixth F1- site, F1- is bonded in a distorted see-saw-like geometry to one Li1+ and three Fe2+ atoms. In the seventh F1- site, F1- is bonded to two Li1+ and two Fe2+ atoms to form distorted FLi2Fe2 trigonal pyramids that share an edgeedge with one OLiFe3 trigonal pyramid and an edgeedge with one FLiFe3 trigonal pyramid. In the eighth F1- site, F1- is bonded in a 4-coordinate geometry to one Li1+ and three Fe2+ atoms.