Materials Data on K2Fe2P2O7F2 by Materials Project

Abstract

K2Fe2P2O7F2 is Esseneite-derived structured and crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. K1+ is bonded in a 8-coordinate geometry to six O2- and two equivalent F1- atoms. There are a spread of K–O bond distances ranging from 2.82–3.21 Å. There are one shorter (2.59 Å) and one longer (2.68 Å) K–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 equivalent PO4 tetrahedra and edges with two equivalent FeO4F2 octahedra. There are two shorter (2.19 Å) and two longer (2.27 Å) Fe–O bond lengths. Both Fe–F bond lengths are 2.01 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 equivalent PO4 tetrahedra and edges with two equivalent FeO4F2 octahedra. There are two shorter (2.14 Å) and two longer (2.18 Å) Fe–O bond lengths. Both Fe–F bond lengths are 2.11 Å. P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four FeO4F2 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 45–57°. There are a spread of P–O bond distances ranging from 1.53–1.65 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent K1+, one Fe2+, and one P5+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent K1+, one Fe2+, and one P5+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two equivalent P5+ atoms. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, two Fe2+, and one P5+ atom. F1- is bonded to two equivalent K1+ and two Fe2+ atoms to form distorted corner-sharing FK2Fe2 tetrahedra.