Materials Data on NaCr2FeO8 by Materials Project
NaCr2FeO8 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with six equivalent CrO4 tetrahedra and edges with two equivalent FeO6 octahedra. There are four shorter (2.53 Å) and two longer (2.54 Å) Na–O bond lengths. Cr6+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with three equivalent NaO6 octahedra and corners with three equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 36–64°. There are a spread of Cr–O bond distances ranging from 1.61–1.70 Å. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six equivalent CrO4 tetrahedra and edges with two equivalent NaO6 octahedra. All Fe–O bond lengths are 2.02 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Na1+ and one Cr6+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Cr6+, and one Fe3+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr6+ and one Fe3+ atom.