Materials Data on Na7Cr2O6 by Materials Project
Na7Cr2O6 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are four inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four O2- atoms to form a mixture of edge and corner-sharing NaO4 trigonal pyramids. There are a spread of Na–O bond distances ranging from 2.32–2.44 Å. In the second Na1+ site, Na1+ is bonded to four O2- atoms to form a mixture of edge and corner-sharing NaO4 trigonal pyramids. There are a spread of Na–O bond distances ranging from 2.31–2.38 Å. In the third Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.47–2.71 Å. In the fourth Na1+ site, Na1+ is bonded to four O2- atoms to form a mixture of distorted edge and corner-sharing NaO4 trigonal pyramids. There are two shorter (2.43 Å) and two longer (2.47 Å) Na–O bond lengths. Cr+2.50+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.83 Å) and two longer (1.84 Å) Cr–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to five Na1+ and one Cr+2.50+ atom to form distorted face-sharing ONa5Cr octahedra. In the second O2- site, O2- is bonded in a 6-coordinate geometry to five Na1+ and one Cr+2.50+ atom. In the third O2- site, O2- is bonded in a 6-coordinate geometry to five Na1+ and one Cr+2.50+ atom.