Materials Data on K2Fe2P2O7F2 by Materials Project
K2Fe2P2O7F2 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. K1+ is bonded in a 6-coordinate geometry to four O2- and two equivalent F1- atoms. There are a spread of K–O bond distances ranging from 2.78–3.14 Å. There are one shorter (3.05 Å) and one longer (3.14 Å) K–F bond lengths. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded in a distorted see-saw-like geometry to four O2- atoms. There are two shorter (1.91 Å) and two longer (2.37 Å) Fe–O bond lengths. In the second Fe2+ site, Fe2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (1.90 Å) and two longer (2.45 Å) Fe–O bond lengths. P5+ is bonded to three O2- and one F1- atom to form corner-sharing PO3F tetrahedra. There is two shorter (1.50 Å) and one longer (1.62 Å) P–O bond length. The P–F bond length is 1.61 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one Fe2+ and one P5+ atom. In the second O2- site, O2- is bonded to two equivalent K1+ and two Fe2+ atoms to form distorted corner-sharing OK2Fe2 tetrahedra. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent K1+, one Fe2+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent P5+ atoms. F1- is bonded in a single-bond geometry to two equivalent K1+ and one P5+ atom.