Materials Data on Na4As2O7 by Materials Project
Na4As2O7 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to five O2- atoms to form distorted NaO5 trigonal bipyramids that share corners with five equivalent AsO4 tetrahedra and edges with two equivalent NaO5 trigonal bipyramids. There are a spread of Na–O bond distances ranging from 2.38–2.46 Å. In the second 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 2.29–2.88 Å. As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share a cornercorner with one AsO4 tetrahedra and corners with five equivalent NaO5 trigonal bipyramids. There is three shorter (1.70 Å) and one longer (1.84 Å) As–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Na1+ and one As5+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Na1+ and two equivalent As5+ atoms. In the third O2- site, O2- is bonded to three Na1+ and one As5+ atom to form distorted edge-sharing ONa3As trigonal pyramids. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Na1+ and one As5+ atom.