Materials Data on NaCoO2 by Materials Project

Abstract

NaCoO2 is Caswellsilverite-like structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. Na1+ is bonded to six O2- atoms to form distorted NaO6 pentagonal pyramids that share corners with nine equivalent CoO6 octahedra, edges with three equivalent CoO6 octahedra, edges with six equivalent NaO6 pentagonal pyramids, and a faceface with one CoO6 octahedra. The corner-sharing octahedra tilt angles range from 11–48°. There are three shorter (2.38 Å) and three longer (2.44 Å) Na–O bond lengths. Co3+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with nine equivalent NaO6 pentagonal pyramids, edges with six equivalent CoO6 octahedra, edges with three equivalent NaO6 pentagonal pyramids, and a faceface with one NaO6 pentagonal pyramid. All Co–O bond lengths are 2.05 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to three equivalent Na1+ and three equivalent Co3+ atoms. In the second O2- site, O2- is bonded to three equivalent Na1+ and three equivalent Co3+ atoms to form edge-sharing ONa3Co3 octahedra.