DOE OSTI2020
Mg2P2O7 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six PO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with two equivalent MgO5 trigonal bipyramids. There are a spread of Mg–O bond distances ranging from 2.06–2.17 Å. In the second Mg2+ site, Mg2+ is bonded to five O2- atoms to form MgO5 trigonal bipyramids that share corners with five PO4 tetrahedra and edges with two equivalent MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.98–2.12 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 MgO6 octahedra, a cornercorner with one PO4 tetrahedra, and corners with two equivalent MgO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 49–53°. There are a spread of P–O bond distances ranging from 1.51–1.62 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three equivalent MgO6 octahedra, a cornercorner with one PO4 tetrahedra, and corners with three equivalent MgO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 35–51°. There is three shorter (1.54 Å) and one longer (1.60 Å) P–O bond length. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one P5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Mg2+ and one P5+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mg2+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Mg2+ and one P5+ atom.