Materials Data on CaAlF5 by Materials Project

Abstract

CaAlF5 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ca2+ is bonded to seven F1- atoms to form distorted CaF7 pentagonal bipyramids that share corners with four equivalent AlF6 octahedra, edges with two equivalent AlF6 octahedra, and edges with two equivalent CaF7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 1–37°. There are a spread of Ca–F bond distances ranging from 2.23–2.57 Å. Al3+ is bonded to six F1- atoms to form AlF6 octahedra that share corners with two equivalent AlF6 octahedra, corners with four equivalent CaF7 pentagonal bipyramids, and edges with two equivalent CaF7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 23°. There are a spread of Al–F bond distances ranging from 1.78–1.90 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a linear geometry to one Ca2+ and one Al3+ atom. In the second F1- site, F1- is bonded in a 2-coordinate geometry to one Ca2+ and two equivalent Al3+ atoms. In the third F1- site, F1- is bonded in a 3-coordinate geometry to two equivalent Ca2+ and one Al3+ atom.