Materials Data on Na2CaP2O7 by Materials Project
Na2CaP2O7 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Na–O bond distances ranging from 2.37–2.91 Å. In the second Na1+ site, Na1+ is bonded in a 4-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.31–3.10 Å. Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.33–2.46 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 three equivalent CaO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–49°. There are a spread of P–O bond distances ranging from 1.53–1.64 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three equivalent CaO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 44–55°. There is three shorter (1.53 Å) and one longer (1.66 Å) P–O bond length. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+, one Ca2+, and one P5+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to three equivalent Na1+, one Ca2+, and one P5+ atom. In the third O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Na1+, one Ca2+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent Na1+ and two P5+ atoms. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+, one Ca2+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a trigonal planar geometry to one Na1+, one Ca2+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Na1+, one Ca2+, and one P5+ atom.