Materials Data on NaCa2Al2As2O11F4 by Materials Project

Abstract

NaCa2Al2As2O11F4 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Na is bonded in a 4-coordinate geometry to three O and two equivalent F atoms. There are a spread of Na–O bond distances ranging from 2.46–2.72 Å. Both Na–F bond lengths are 2.19 Å. Ca is bonded in a 8-coordinate geometry to five O and three F atoms. There are a spread of Ca–O bond distances ranging from 2.36–2.83 Å. There are a spread of Ca–F bond distances ranging from 2.38–2.41 Å. Al is bonded to four O and two F atoms to form AlO4F2 octahedra that share a cornercorner with one AlO4F2 octahedra and corners with two AsO4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. There are a spread of Al–O bond distances ranging from 1.87–1.96 Å. There is one shorter (1.80 Å) and one longer (1.92 Å) Al–F bond length. There are two inequivalent As sites. In the first As site, As is bonded to four O atoms to form AsO4 tetrahedra that share corners with two equivalent AlO4F2 octahedra. The corner-sharing octahedral tilt angles are 52°. There is three shorter (1.71 Å) and one longer (1.76 Å) As–O bond length. In the second As site, As is bonded to four O atoms to form AsO4 tetrahedra that share corners with two equivalent AlO4F2 octahedra. The corner-sharing octahedral tilt angles are 59°. There are a spread of As–O bond distances ranging from 1.69–1.74 Å. There are eight inequivalent O sites. In the first O site, O is bonded in a water-like geometry to one Na and one As atom. In the second O site, O is bonded in a bent 150 degrees geometry to two equivalent Al atoms. In the third O site, O is bonded in a distorted single-bond geometry to one Ca and one Al atom. In the fourth O site, O is bonded in a 4-coordinate geometry to one Na, two equivalent Ca, and one As atom. In the fifth O site, O is bonded in a bent 120 degrees geometry to one Al and one As atom. In the sixth O site, O is bonded in a 4-coordinate geometry to one Na, two equivalent Ca, and one As atom. In the seventh O site, O is bonded in a 1-coordinate geometry to two equivalent Ca and one As atom. In the eighth O site, O is bonded in a distorted trigonal planar geometry to one Ca, one Al, and one As atom. There are two inequivalent F sites. In the first F site, F is bonded in a 3-coordinate geometry to one Na, one Ca, and one Al atom. In the second F site, F is bonded in a distorted trigonal planar geometry to two equivalent Ca and one Al atom.