Materials Data on Na2Sr7Al6F34 by Materials Project
Na2Sr7Al6F34 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six F1- atoms to form distorted NaF6 octahedra that share corners with two equivalent NaF6 octahedra and corners with four equivalent AlF6 octahedra. The corner-sharing octahedra tilt angles range from 55–67°. There are two shorter (2.20 Å) and four longer (2.43 Å) Na–F bond lengths. In the second Na1+ site, Na1+ is bonded to six F1- atoms to form NaF6 octahedra that share corners with two equivalent NaF6 octahedra and corners with four equivalent AlF6 octahedra. The corner-sharing octahedra tilt angles range from 44–67°. There are two shorter (2.23 Å) and four longer (2.29 Å) Na–F bond lengths. There are three inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to nine F1- atoms. There are a spread of Sr–F bond distances ranging from 2.43–2.93 Å. In the second Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to nine F1- atoms. There are a spread of Sr–F bond distances ranging from 2.58–2.94 Å. In the third Sr2+ site, Sr2+ is bonded in a distorted q6 geometry to ten F1- atoms. There are six shorter (2.58 Å) and four longer (2.87 Å) Sr–F bond lengths. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six F1- atoms to form AlF6 octahedra that share a cornercorner with one AlF6 octahedra and corners with two NaF6 octahedra. The corner-sharing octahedra tilt angles range from 36–55°. There are a spread of Al–F bond distances ranging from 1.80–1.86 Å. In the second Al3+ site, Al3+ is bonded to six F1- atoms to form corner-sharing AlF6 octahedra. The corner-sharing octahedral tilt angles are 36°. There are a spread of Al–F bond distances ranging from 1.81–1.85 Å. There are ten inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted single-bond geometry to three Sr2+ and one Al3+ atom. In the second F1- site, F1- is bonded in a distorted single-bond geometry to two Sr2+ and one Al3+ atom. In the third F1- site, F1- is bonded in a 1-coordinate geometry to three Sr2+ and one Al3+ atom. In the fourth F1- site, F1- is bonded in a 4-coordinate geometry to one Na1+, two Sr2+, and one Al3+ atom. In the fifth F1- site, F1- is bonded in a 3-coordinate geometry to one Na1+, one Sr2+, and one Al3+ atom. In the sixth F1- site, F1- is bonded in a 1-coordinate geometry to three Sr2+ and one Al3+ atom. In the seventh F1- site, F1- is bonded in a distorted linear geometry to one Sr2+ and one Al3+ atom. In the eighth F1- site, F1- is bonded to two Na1+ and two equivalent Sr2+ atoms to form corner-sharing FNa2Sr2 tetrahedra. In the ninth F1- site, F1- is bonded in a 1-coordinate geometry to two Sr2+ and one Al3+ atom. In the tenth F1- site, F1- is bonded in a bent 150 degrees geometry to two Al3+ atoms.