DOI: 10.17188/1305477
title: Materials Data on Na8Co2O7 by Materials Project

description: Na8Co2O7 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are eight inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share a cornercorner with one NaO6 octahedra, a cornercorner with one NaO4 tetrahedra, corners with four CoO4 tetrahedra, corners with two equivalent NaO4 trigonal pyramids, an edgeedge with one NaO6 octahedra, and edges with two NaO4 tetrahedra. The corner-sharing octahedral tilt angles are 93°. There are a spread of Na–O bond distances ranging from 2.27–2.40 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 2.32–2.64 Å. In the third Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with two equivalent NaO6 octahedra, corners with five NaO4 tetrahedra, edges with two NaO4 tetrahedra, edges with four CoO4 tetrahedra, and an edgeedge with one NaO4 trigonal pyramid. The corner-sharing octahedral tilt angles are 24°. There are a spread of Na–O bond distances ranging from 2.43–2.63 Å. In the fourth Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share corners with two equivalent NaO6 octahedra, corners with three NaO4 tetrahedra, corners with three CoO4 tetrahedra, corners with two equivalent NaO4 trigonal pyramids, an edgeedge with one NaO6 octahedra, an edgeedge with one NaO4 tetrahedra, and an edgeedge with one CoO4 tetrahedra. The corner-sharing octahedra tilt angles range from 14–55°. There are a spread of Na–O bond distances ranging from 2.30–2.48 Å. In the fifth 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 2.31–2.76 Å. In the sixth 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 2.23–2.51 Å. In the seventh Na1+ site, Na1+ is bonded to four O2- atoms to form NaO4 tetrahedra that share corners with two equivalent NaO6 octahedra, corners with two equivalent NaO4 tetrahedra, corners with four CoO4 tetrahedra, a cornercorner with one NaO4 trigonal pyramid, an edgeedge with one NaO4 tetrahedra, and an edgeedge with one NaO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 28–92°. There are a spread of Na–O bond distances ranging from 2.29–2.44 Å. In the eighth Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 trigonal pyramids that share corners with two CoO4 tetrahedra, corners with five NaO4 tetrahedra, an edgeedge with one NaO6 octahedra, an edgeedge with one NaO4 tetrahedra, and an edgeedge with one CoO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.29–2.42 Å. There are two inequivalent Co3+ sites. In the first Co3+ site, Co3+ is bonded to four O2- atoms to form CoO4 tetrahedra that share a cornercorner with one CoO4 tetrahedra, corners with six NaO4 tetrahedra, a cornercorner with one NaO4 trigonal pyramid, and edges with two equivalent NaO6 octahedra. There are a spread of Co–O bond distances ranging from 1.83–1.96 Å. In the second Co3+ site, Co3+ is bonded to four O2- atoms to form CoO4 tetrahedra that share a cornercorner with one CoO4 tetrahedra, corners with five NaO4 tetrahedra, a cornercorner with one NaO4 trigonal pyramid, edges with two equivalent NaO6 octahedra, an edgeedge with one NaO4 tetrahedra, and an edgeedge with one NaO4 trigonal pyramid. There are a spread of Co–O bond distances ranging from 1.83–1.96 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to five Na1+ and one Co3+ atom to form distorted ONa5Co octahedra that share a cornercorner with one ONa5Co octahedra, a cornercorner with one ONa6Co pentagonal bipyramid, and edges with four ONa5Co octahedra. The corner-sharing octahedral tilt angles are 63°. In the second O2- site, O2- is bonded in a 6-coordinate geometry to four Na1+ and two Co3+ atoms. In the third O2- site, O2- is bonded to five Na1+ and one Co3+ atom to form distorted ONa5Co octahedra that share corners with two ONa5Co octahedra, edges with two ONa5Co octahedra, and edges with two equivalent ONa6Co pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 7–63°. In the fourth O2- site, O2- is bonded in a 7-coordinate geometry to six Na1+ and one Co3+ atom. In the fifth O2- site, O2- is bonded to five Na1+ and one Co3+ atom to form distorted ONa5Co octahedra that share a cornercorner with one ONa5Co octahedra, a cornercorner with one ONa6Co pentagonal bipyramid, edges with two equivalent ONa5Co octahedra, and edges with two equivalent ONa6Co pentagonal bipyramids. The corner-sharing octahedral tilt angles are 7°. In the sixth O2- site, O2- is bonded in a 6-coordinate geometry to five Na1+ and one Co3+ atom. In the seventh O2- site, O2- is bonded to six Na1+ and one Co3+ atom to form distorted ONa6Co pentagonal bipyramids that share corners with two ONa5Co octahedra, edges with four ONa5Co octahedra, and an edgeedge with one ONa6Co pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 2–32°.