Materials Data on KCaFe2F9 by Materials Project
KCaFe2F9 crystallizes in the orthorhombic C222_1 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 10-coordinate geometry to ten F1- atoms. There are a spread of K–F bond distances ranging from 2.89–3.21 Å. In the second K1+ site, K1+ is bonded in a 10-coordinate geometry to ten F1- atoms. There are a spread of K–F bond distances ranging from 2.93–3.20 Å. There are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six F1- atoms to form distorted CaF6 octahedra that share corners with six FeF6 octahedra. The corner-sharing octahedra tilt angles range from 20–60°. There are two shorter (2.19 Å) and four longer (2.42 Å) Ca–F bond lengths. In the second Ca2+ site, Ca2+ is bonded to six F1- atoms to form distorted CaF6 octahedra that share corners with six FeF6 octahedra. The corner-sharing octahedra tilt angles range from 29–61°. There are a spread of Ca–F bond distances ranging from 2.24–2.43 Å. There are three inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six F1- atoms to form FeF6 octahedra that share corners with three CaF6 octahedra and corners with three FeF6 octahedra. The corner-sharing octahedra tilt angles range from 24–60°. There are a spread of Fe–F bond distances ranging from 1.94–2.00 Å. In the second Fe3+ site, Fe3+ is bonded to six F1- atoms to form FeF6 octahedra that share corners with three equivalent CaF6 octahedra and corners with three FeF6 octahedra. The corner-sharing octahedra tilt angles range from 23–59°. There are a spread of Fe–F bond distances ranging from 1.94–2.00 Å. In the third Fe3+ site, Fe3+ is bonded to six F1- atoms to form FeF6 octahedra that share corners with three CaF6 octahedra and corners with three FeF6 octahedra. The corner-sharing octahedra tilt angles range from 20–61°. There are a spread of Fe–F bond distances ranging from 1.91–1.97 Å. There are fourteen inequivalent F1- sites. In the first F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent K1+, one Ca2+, and one Fe3+ atom. In the second F1- site, F1- is bonded in a 2-coordinate geometry to two K1+, one Ca2+, and one Fe3+ atom. In the third F1- site, F1- is bonded in a bent 150 degrees geometry to two Fe3+ atoms. In the fourth F1- site, F1- is bonded in a distorted bent 150 degrees geometry to one K1+, one Ca2+, and one Fe3+ atom. In the fifth F1- site, F1- is bonded in a bent 150 degrees geometry to one Ca2+ and one Fe3+ atom. In the sixth F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent Fe3+ atoms. In the seventh F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent Fe3+ atoms. In the eighth F1- site, F1- is bonded in a distorted bent 150 degrees geometry to one K1+, one Ca2+, and one Fe3+ atom. In the ninth F1- site, F1- is bonded in a 2-coordinate geometry to two K1+, one Ca2+, and one Fe3+ atom. In the tenth F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent K1+, one Ca2+, and one Fe3+ atom. In the eleventh F1- site, F1- is bonded in a 2-coordinate geometry to two K1+, one Ca2+, and one Fe3+ atom. In the twelfth F1- site, F1- is bonded in a bent 150 degrees geometry to two Fe3+ atoms. In the thirteenth F1- site, F1- is bonded in a 2-coordinate geometry to two K1+, one Ca2+, and one Fe3+ atom. In the fourteenth F1- site, F1- is bonded in a bent 150 degrees geometry to one K1+ and two Fe3+ atoms.