Materials Data on Na6CoO4 by Materials Project
Na6CoO4 crystallizes in the cubic I-43m space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four O2- atoms to form NaO4 tetrahedra that share a cornercorner with one CoO4 tetrahedra, corners with nine equivalent NaO4 tetrahedra, and an edgeedge with one CoO4 tetrahedra. There are two shorter (2.32 Å) and two longer (2.34 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Na–O bond distances ranging from 2.28–2.74 Å. Co2+ is bonded to four O2- atoms to form CoO4 tetrahedra that share corners with three equivalent NaO4 tetrahedra, corners with three equivalent CoO4 tetrahedra, and edges with three equivalent NaO4 tetrahedra. There are three shorter (2.05 Å) and one longer (2.36 Å) Co–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 7-coordinate geometry to six Na1+ and one Co2+ atom. In the second O2- site, O2- is bonded in a tetrahedral geometry to four equivalent Co2+ atoms. In the third O2- site, O2- is bonded in a 8-coordinate geometry to eight Na1+ atoms.