Materials Data on CaAlF5 by Materials Project
CaAlF5 crystallizes in the monoclinic P2_1/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 14–44°. There are a spread of Ca–F bond distances ranging from 2.23–2.62 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 1.77–1.90 Å. There are five inequivalent F1- sites. In the first F1- site, F1- is bonded in a 3-coordinate geometry to two equivalent Ca2+ and one Al3+ atom. In the second F1- site, F1- is bonded in a distorted bent 150 degrees geometry to one Ca2+ and two equivalent Al3+ atoms. In the third F1- site, F1- is bonded in a distorted bent 150 degrees geometry to one Ca2+ and one Al3+ atom. In the fourth F1- site, F1- is bonded in a distorted linear geometry to one Ca2+ and one Al3+ atom. In the fifth F1- site, F1- is bonded in a distorted trigonal non-coplanar geometry to two equivalent Ca2+ and one Al3+ atom.