Materials Data on NaCr12Si8BrO28 by Materials Project

Abstract

NaCr12Si8O28Br crystallizes in the tetragonal I4mm space group. The structure is three-dimensional. Na1+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All Na–O bond lengths are 2.46 Å. There are three inequivalent Cr2+ sites. In the first Cr2+ site, Cr2+ is bonded in a square co-planar geometry to four O2- and one Br1- atom. There are two shorter (2.06 Å) and two longer (2.07 Å) Cr–O bond lengths. The Cr–Br bond length is 3.48 Å. In the second Cr2+ site, Cr2+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.05 Å) and two longer (2.06 Å) Cr–O bond lengths. In the third Cr2+ site, Cr2+ is bonded in a square co-planar geometry to four O2- and one Br1- atom. All Cr–O bond lengths are 2.05 Å. The Cr–Br bond length is 3.41 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.68 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.68 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Cr2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a trigonal planar geometry to two equivalent Cr2+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Cr2+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Cr2+ and one Si4+ atom. Br1- is bonded in a 8-coordinate geometry to eight Cr2+ atoms.