Materials Data on Na2Cr2O5 by Materials Project
Na2Cr2O5 crystallizes in the orthorhombic Ima2 space group. The structure is three-dimensional. Na1+ is bonded in a 7-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.30–2.92 Å. There are two inequivalent Cr4+ sites. In the first Cr4+ site, Cr4+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with four equivalent CrO6 octahedra and corners with two equivalent CrO4 tetrahedra. The corner-sharing octahedral tilt angles are 14°. There are a spread of Cr–O bond distances ranging from 1.94–2.08 Å. In the second Cr4+ site, Cr4+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with two equivalent CrO6 octahedra and corners with two equivalent CrO4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. There are a spread of Cr–O bond distances ranging from 1.75–1.85 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to four equivalent Na1+ and two equivalent Cr4+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three equivalent Na1+ and two Cr4+ atoms. In the third O2- site, O2- is bonded to two equivalent Na1+ and two equivalent Cr4+ atoms to form distorted corner-sharing ONa2Cr2 tetrahedra.