Materials Data on K2Al2O2F9 by Materials Project
K2Al2F9O2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of four water molecules and one K2Al2F9 framework. In the K2Al2F9 framework, K is bonded in a 6-coordinate geometry to six F atoms. There are a spread of K–F bond distances ranging from 2.53–2.74 Å. Al is bonded to six F atoms to form corner-sharing AlF6 octahedra. The corner-sharing octahedra tilt angles range from 0–8°. There are a spread of Al–F bond distances ranging from 1.74–1.90 Å. There are five inequivalent F sites. In the first F site, F is bonded in a linear geometry to two equivalent Al atoms. In the second F site, F is bonded in a distorted single-bond geometry to two equivalent K and one Al atom. In the third F site, F is bonded in a distorted single-bond geometry to two equivalent K and one Al atom. In the fourth F site, F is bonded in a distorted single-bond geometry to two equivalent K and one Al atom. In the fifth F site, F is bonded in a linear geometry to two equivalent Al atoms.