DOE OSTI2020
CrPO4 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. there are two inequivalent Cr3+ sites. In the first Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with two equivalent CrO6 octahedra, corners with four PO4 tetrahedra, an edgeedge with one CrO6 octahedra, and an edgeedge with one PO4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. There are a spread of Cr–O bond distances ranging from 1.99–2.05 Å. In the second Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with four equivalent CrO6 octahedra and corners with six PO4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. There are two shorter (2.01 Å) and four longer (2.02 Å) Cr–O bond lengths. 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 four CrO6 octahedra and an edgeedge with one CrO6 octahedra. The corner-sharing octahedra tilt angles range from 39–54°. There is two shorter (1.51 Å) and two longer (1.61 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 six CrO6 octahedra. The corner-sharing octahedra tilt angles range from 38–55°. There is two shorter (1.52 Å) and two longer (1.59 Å) P–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Cr3+ and one P5+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two Cr3+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Cr3+ and one P5+ atom.