Materials Data on Sr5Al2F16 by Materials Project

Abstract

Sr5Al2F16 crystallizes in the orthorhombic Ccce space group. The structure is three-dimensional. there are three inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of Sr–F bond distances ranging from 2.51–2.65 Å. In the second Sr2+ site, Sr2+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are four shorter (2.47 Å) and four longer (2.62 Å) Sr–F bond lengths. In the third Sr2+ site, Sr2+ is bonded to eight F1- atoms to form distorted SrF8 hexagonal bipyramids that share corners with two equivalent AlF6 octahedra and edges with two equivalent AlF6 octahedra. The corner-sharing octahedral tilt angles are 59°. There are a spread of Sr–F bond distances ranging from 2.50–2.62 Å. Al3+ is bonded to six F1- atoms to form AlF6 octahedra that share corners with two equivalent SrF8 hexagonal bipyramids and edges with two equivalent SrF8 hexagonal bipyramids. There are a spread of Al–F bond distances ranging from 1.81–1.85 Å. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded in a 3-coordinate geometry to two Sr2+ and one Al3+ atom. In the second F1- site, F1- is bonded in a 1-coordinate geometry to two Sr2+ and one Al3+ atom. In the third F1- site, F1- is bonded to four Sr2+ atoms to form a mixture of distorted edge and corner-sharing FSr4 tetrahedra. In the fourth F1- site, F1- is bonded in a distorted single-bond geometry to two Sr2+ and one Al3+ atom.