Materials Data on K2CaP2O7 by Materials Project
K2CaP2O7 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.82–3.14 Å. In the second K1+ site, K1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.80–3.14 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 2.32–2.42 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 8–46°. There is three shorter (1.53 Å) and one longer (1.66 Å) P–O bond length. 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 16–41°. 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 K1+, one Ca2+, and one P5+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one Ca2+, and one P5+ atom. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent K1+ and two P5+ atoms. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to three equivalent K1+, one Ca2+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one Ca2+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to three equivalent K1+, one Ca2+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to three K1+, one Ca2+, and one P5+ atom.