Materials Data on KFeF4 by Materials Project
KFeF4 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. K1+ is bonded in a 7-coordinate geometry to seven F1- atoms. There are a spread of K–F bond distances ranging from 2.70–2.85 Å. Fe3+ is bonded to six F1- atoms to form corner-sharing FeF6 octahedra. The corner-sharing octahedra tilt angles range from 0–29°. There is two shorter (1.90 Å) and four longer (2.00 Å) Fe–F bond length. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded to three equivalent K1+ and one Fe3+ atom to form a mixture of distorted corner and edge-sharing FK3Fe tetrahedra. In the second F1- site, F1- is bonded in a linear geometry to two equivalent Fe3+ atoms. In the third F1- site, F1- is bonded in a distorted bent 150 degrees geometry to one K1+ and two equivalent Fe3+ atoms.