Materials Data on Na5CoO4 by Materials Project

Abstract

Na5CoO4 crystallizes in the orthorhombic Pmn2_1 space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first 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 2.32–2.71 Å. In the second Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share corners with two equivalent CoO4 tetrahedra, corners with six NaO4 tetrahedra, an edgeedge with one NaO4 tetrahedra, and an edgeedge with one CoO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.27–2.46 Å. In the third Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share corners with four equivalent NaO4 tetrahedra, corners with four equivalent CoO4 tetrahedra, and edges with two equivalent NaO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.33–2.55 Å. Co3+ is bonded to four O2- atoms to form CoO4 tetrahedra that share corners with eight NaO4 tetrahedra and edges with two equivalent NaO4 tetrahedra. There are a spread of Co–O bond distances ranging from 1.88–1.93 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to five Na1+ and one Co3+ atom to form a mixture of distorted corner and edge-sharing ONa5Co pentagonal pyramids. The corner-sharing octahedra tilt angles range from 69–71°. In the second O2- site, O2- is bonded in a 4-coordinate geometry to seven Na1+ and one Co3+ atom. In the third O2- site, O2- is bonded to five Na1+ and one Co3+ atom to form a mixture of corner and edge-sharing ONa5Co octahedra. The corner-sharing octahedra tilt angles range from 40–53°.