DOI: 10.17188/1304396
title: Materials Data on Li3Fe2F7 by Materials Project

description: Li3Fe2F7 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to four F1- atoms to form LiF4 tetrahedra that share corners with three equivalent FeF6 octahedra, corners with two equivalent LiF4 tetrahedra, corners with three equivalent FeF5 trigonal bipyramids, and an edgeedge with one LiF5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 25–60°. There are a spread of Li–F bond distances ranging from 1.84–1.93 Å. In the second Li1+ site, Li1+ is bonded to four F1- atoms to form LiF4 tetrahedra that share a cornercorner with one FeF6 octahedra, corners with two equivalent LiF4 tetrahedra, corners with two equivalent FeF5 trigonal bipyramids, corners with three equivalent LiF5 trigonal bipyramids, and an edgeedge with one FeF6 octahedra. The corner-sharing octahedral tilt angles are 64°. There are a spread of Li–F bond distances ranging from 1.87–2.00 Å. In the third Li1+ site, Li1+ is bonded to five F1- atoms to form distorted LiF5 trigonal bipyramids that share corners with three equivalent LiF4 tetrahedra, a cornercorner with one FeF5 trigonal bipyramid, edges with two equivalent FeF6 octahedra, an edgeedge with one LiF4 tetrahedra, and an edgeedge with one FeF5 trigonal bipyramid. There are a spread of Li–F bond distances ranging from 1.94–2.16 Å. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to five F1- atoms to form distorted FeF5 trigonal bipyramids that share corners with two equivalent FeF6 octahedra, corners with five LiF4 tetrahedra, a cornercorner with one LiF5 trigonal bipyramid, an edgeedge with one FeF6 octahedra, and an edgeedge with one LiF5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 51–55°. There are a spread of Fe–F bond distances ranging from 2.01–2.11 Å. In the second Fe2+ site, Fe2+ is bonded to six F1- atoms to form distorted FeF6 octahedra that share corners with four LiF4 tetrahedra, corners with two equivalent FeF5 trigonal bipyramids, an edgeedge with one FeF6 octahedra, an edgeedge with one LiF4 tetrahedra, an edgeedge with one FeF5 trigonal bipyramid, and edges with two equivalent LiF5 trigonal bipyramids. There are a spread of Fe–F bond distances ranging from 1.99–2.30 Å. There are seven inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted trigonal planar geometry to one Li1+ and two Fe2+ atoms. In the second F1- site, F1- is bonded in a distorted see-saw-like geometry to three Li1+ and one Fe2+ atom. In the third F1- site, F1- is bonded to two Li1+ and two Fe2+ atoms to form distorted corner-sharing FLi2Fe2 tetrahedra. In the fourth F1- site, F1- is bonded in a 3-coordinate geometry to two Li1+ and one Fe2+ atom. In the fifth F1- site, F1- is bonded to one Li1+ and three Fe2+ atoms to form distorted FLiFe3 trigonal pyramids that share corners with three equivalent FLi2Fe2 tetrahedra and an edgeedge with one FLiFe3 trigonal pyramid. In the sixth F1- site, F1- is bonded in a distorted trigonal planar geometry to two Li1+ and one Fe2+ atom. In the seventh F1- site, F1- is bonded in a T-shaped geometry to two Li1+ and one Fe2+ atom.