Materials Data on Li2FePO4F by Materials Project
Li2FePO4F crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are three inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a 6-coordinate geometry to four O2- and two F1- atoms. There are a spread of Li–O bond distances ranging from 2.06–2.39 Å. There are one shorter (1.88 Å) and one longer (2.45 Å) Li–F bond lengths. In the second Li1+ site, Li1+ is bonded to four O2- and one F1- atom to form distorted LiO4F trigonal bipyramids that share corners with two equivalent FeO4F2 octahedra, corners with four PO4 tetrahedra, and edges with two equivalent FeO4F2 octahedra. The corner-sharing octahedral tilt angles are 68°. There are a spread of Li–O bond distances ranging from 2.09–2.19 Å. The Li–F bond length is 1.94 Å. In the third Li1+ site, Li1+ is bonded in a 6-coordinate geometry to four O2- and two F1- atoms. There are a spread of Li–O bond distances ranging from 2.05–2.26 Å. There are one shorter (2.43 Å) and one longer (2.74 Å) Li–F bond lengths. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to four O2- and two equivalent F1- atoms to form FeO4F2 octahedra that share corners with four PO4 tetrahedra, edges with two equivalent FeO4F2 octahedra, and edges with two equivalent LiO4F trigonal bipyramids. There are two shorter (2.07 Å) and two longer (2.15 Å) Fe–O bond lengths. Both Fe–F bond lengths are 2.18 Å. In the second Fe2+ site, Fe2+ is bonded to four O2- and two equivalent F1- atoms to form FeO4F2 octahedra that share corners with four PO4 tetrahedra, corners with two equivalent LiO4F trigonal bipyramids, and edges with two equivalent FeO4F2 octahedra. There are two shorter (2.07 Å) and two longer (2.11 Å) Fe–O bond lengths. Both Fe–F bond lengths are 2.20 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four FeO4F2 octahedra and corners with two equivalent LiO4F trigonal bipyramids. The corner-sharing octahedra tilt angles range from 57–59°. All P–O bond lengths are 1.56 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four FeO4F2 octahedra and corners with two equivalent LiO4F trigonal bipyramids. The corner-sharing octahedra tilt angles range from 53–58°. There is one shorter (1.54 Å) and three longer (1.56 Å) P–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Li1+, two equivalent Fe2+, and one P5+ atom. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Li1+, one Fe2+, and one P5+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, two equivalent Fe2+, and one P5+ atom. In the fourth O2- site, O2- is bonded to three Li1+ and one P5+ atom to form distorted corner-sharing OLi3P tetrahedra. In the fifth O2- site, O2- is bonded to two Li1+, one Fe2+, and one P5+ atom to form distorted OLi2FeP trigonal pyramids that share corners with two equivalent OLi3P tetrahedra and corners with three equivalent OLi2FeP trigonal pyramids. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Li1+ and one P5+ atom. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a 3-coordinate geometry to three Li1+ and two equivalent Fe2+ atoms. In the second F1- site, F1- is bonded in a 1-coordinate geometry to four Li1+ and two equivalent Fe2+ atoms.