Materials Data on NaCo2P2O9 by Materials Project
NaCo2P2O9 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with six CoO6 octahedra, corners with four equivalent PO4 tetrahedra, and an edgeedge with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 52–70°. There are a spread of Na–O bond distances ranging from 2.31–2.64 Å. There are two inequivalent Co+3.50+ sites. In the first Co+3.50+ site, Co+3.50+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two equivalent CoO6 octahedra, corners with four equivalent NaO6 octahedra, corners with three equivalent PO4 tetrahedra, and an edgeedge with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 52–70°. There are a spread of Co–O bond distances ranging from 1.91–2.07 Å. In the second Co+3.50+ site, Co+3.50+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two equivalent NaO6 octahedra, corners with two equivalent CoO6 octahedra, corners with four PO4 tetrahedra, and edges with two equivalent CoO6 octahedra. The corner-sharing octahedra tilt angles range from 53–64°. There are a spread of Co–O bond distances ranging from 1.94–2.04 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with five CoO6 octahedra and an edgeedge with one NaO6 octahedra. The corner-sharing octahedra tilt angles range from 17–52°. There are a spread of P–O bond distances ranging from 1.50–1.58 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent CoO6 octahedra, corners with four equivalent NaO6 octahedra, and an edgeedge with one CoO6 octahedra. The corner-sharing octahedra tilt angles range from 23–72°. There is three shorter (1.55 Å) and one longer (1.56 Å) P–O bond length. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to three Co+3.50+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Co+3.50+, and one P5+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Co+3.50+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted linear geometry to one Co+3.50+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, one Co+3.50+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Na1+, one Co+3.50+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Co+3.50+ and one P5+ atom.