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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Hf2P2O9 by Materials Project

Hf2P2O9 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Hf4+ sites. In the first Hf4+ site, Hf4+ is bonded to seven O2- atoms to form HfO7 pentagonal bipyramids that share a cornercorner with one HfO6 octahedra, corners with four PO4 tetrahedra, an edgeedge with one HfO6 octahedra, an edgeedge with one HfO7 pentagonal bipyramid, and an edgeedge with one PO4 tetrahedra. The corner-sharing octahedral tilt angles are 36°. There are a spread of Hf–O bond distances ranging from 2.05–2.33 Å. In the second Hf4+ site, Hf4+ is bonded to six O2- atoms to form HfO6 octahedra that share a cornercorner with one HfO7 pentagonal bipyramid, corners with four PO4 tetrahedra, an edgeedge with one HfO6 octahedra, and an edgeedge with one HfO7 pentagonal bipyramid. There are a spread of Hf–O bond distances ranging from 2.01–2.15 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 HfO6 octahedra, a cornercorner with one HfO7 pentagonal bipyramid, and an edgeedge with one HfO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 23–28°. There is two shorter (1.52 Å) and two longer (1.57 Å) P–O bond length. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one HfO6 octahedra and corners with three equivalent HfO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 39°. There is two shorter (1.54 Å) and two longer (1.55 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 two equivalent Hf4+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Hf4+ and one P5+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two Hf4+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Hf4+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Hf4+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Hf4+ atoms. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Hf4+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfP2O7 by Materials Project

HfP2O7 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Hf4+ sites. In the first Hf4+ site, Hf4+ is bonded to six O2- atoms to form HfO6 octahedra that share corners with six PO4 tetrahedra. There are four shorter (2.07 Å) and two longer (2.08 Å) Hf–O bond lengths. In the second Hf4+ site, Hf4+ is bonded to six O2- atoms to form HfO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Hf–O bond distances ranging from 2.06–2.08 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 HfO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 28–46°. There are a spread of P–O bond distances ranging from 1.52–1.62 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three HfO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 36–48°. There are a spread of P–O bond distances ranging from 1.52–1.62 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Hf4+ and one P5+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Hf4+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Hf4+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Hf4+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Hf4+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Hf4+ and one P5+ atom.

36 MATERIALS SCIENCE↗