Materials Data on Li2FeF4 by Materials Project

Abstract

Li2FeF4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to four F1- atoms to form LiF4 tetrahedra that share corners with two equivalent FeF6 octahedra, corners with two equivalent LiF4 tetrahedra, a cornercorner with one LiF4 trigonal pyramid, and an edgeedge with one FeF6 octahedra. The corner-sharing octahedra tilt angles range from 49–78°. There is one shorter (1.84 Å) and three longer (1.93 Å) Li–F bond length. In the second 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, and a cornercorner with one LiF4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 57–68°. There is three shorter (1.90 Å) and one longer (1.91 Å) Li–F bond length. In the third Li1+ site, Li1+ is bonded to four F1- atoms to form distorted LiF4 trigonal pyramids that share corners with three equivalent FeF6 octahedra and corners with two LiF4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–66°. There are a spread of Li–F bond distances ranging from 1.90–2.01 Å. In the fourth Li1+ site, Li1+ is bonded in a 5-coordinate geometry to five F1- atoms. There are a spread of Li–F bond distances ranging from 1.89–2.51 Å. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to six F1- atoms to form distorted FeF6 octahedra that share corners with five LiF4 tetrahedra, corners with three equivalent LiF4 trigonal pyramids, and an edgeedge with one LiF4 tetrahedra. There are a spread of Fe–F bond distances ranging from 1.99–2.33 Å. In the second Fe2+ site, Fe2+ is bonded in a 5-coordinate geometry to five F1- atoms. There are a spread of Fe–F bond distances ranging from 1.95–2.27 Å. There are eight inequivalent F1- sites. In the first F1- site, F1- is bonded to two Li1+ and two Fe2+ atoms to form a mixture of distorted edge and corner-sharing FLi2Fe2 trigonal pyramids. In the second F1- site, F1- is bonded in a 3-coordinate geometry to two Li1+ and one Fe2+ atom. In the third F1- site, F1- is bonded in a trigonal planar geometry to two Li1+ and one Fe2+ atom. In the fourth F1- site, F1- is bonded in a 4-coordinate geometry to three Li1+ and one Fe2+ atom. In the fifth F1- site, F1- is bonded in a trigonal planar geometry to two Li1+ and one Fe2+ atom. In the sixth F1- site, F1- is bonded to two Li1+ and two Fe2+ atoms to form a mixture of distorted edge and corner-sharing FLi2Fe2 tetrahedra. In the seventh F1- site, F1- is bonded in a distorted trigonal planar geometry to two Li1+ and one Fe2+ atom. In the eighth F1- site, F1- is bonded to two Li1+ and two Fe2+ atoms to form distorted corner-sharing FLi2Fe2 tetrahedra.