DOE OSTI2020
FeP2O7 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Fe sites. In the first Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share a cornercorner with one FeO6 octahedra and corners with six PO4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. There are a spread of Fe–O bond distances ranging from 1.99–2.07 Å. In the second Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share a cornercorner with one FeO6 octahedra and corners with six PO4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. There are a spread of Fe–O bond distances ranging from 1.99–2.06 Å. In the third Fe site, Fe is bonded to six O atoms to form distorted FeO6 octahedra that share a cornercorner with one FeO6 octahedra, corners with four PO4 tetrahedra, and an edgeedge with one PO4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. There are a spread of Fe–O bond distances ranging from 1.94–2.52 Å. In the fourth Fe site, Fe is bonded to six O atoms to form distorted FeO6 octahedra that share a cornercorner with one FeO6 octahedra, corners with four PO4 tetrahedra, and an edgeedge with one PO4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. There are a spread of Fe–O bond distances ranging from 1.94–2.49 Å. There are eight inequivalent P sites. In the first P site, P is bonded to four O atoms to form PO4 tetrahedra that share corners with two FeO6 octahedra, a cornercorner with one PO4 tetrahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 43–47°. There are a spread of P–O bond distances ranging from 1.52–1.61 Å. In the second P site, P is bonded to four O atoms to form PO4 tetrahedra that share corners with two FeO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 36–41°. There are a spread of P–O bond distances ranging from 1.52–1.61 Å. In the third P site, P is bonded to four O atoms to form PO4 tetrahedra that share corners with three FeO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–47°. There is three shorter (1.53 Å) and one longer (1.61 Å) P–O bond length. In the fourth P site, P is bonded to four O atoms to form PO4 tetrahedra that share corners with two FeO6 octahedra, a cornercorner with one PO4 tetrahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 43–47°. There are a spread of P–O bond distances ranging from 1.52–1.61 Å. In the fifth P site, P is bonded to four O atoms to form PO4 tetrahedra that share corners with three FeO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–43°. There are a spread of P–O bond distances ranging from 1.52–1.62 Å. In the sixth P site, P is bonded to four O atoms to form PO4 tetrahedra that share corners with two FeO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 36–42°. There are a spread of P–O bond distances ranging from 1.52–1.61 Å. In the seventh P site, P is bonded to four O atoms to form PO4 tetrahedra that share corners with three FeO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–47°. There is three shorter (1.53 Å) and one longer (1.61 Å) P–O bond length. In the eighth P site, P is bonded to four O atoms to form PO4 tetrahedra that share corners with three FeO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–43°. There are a spread of P–O bond distances ranging from 1.52–1.62 Å. There are twenty-eight inequivalent O sites. In the first O site, O is bonded in a 2-coordinate geometry to two Fe and one P atom. In the second O site, O is bonded in a distorted bent 150 degrees geometry to one Fe and one P atom. In the third O site, O is bonded in a distorted bent 120 degrees geometry to two P atoms. In the fourth O site, O is bonded in a distorted bent 120 degrees geometry to one Fe and one P atom. In the fifth O site, O is bonded in a distorted bent 150 degrees geometry to one Fe and one P atom. In the sixth O site, O is bonded in a bent 150 degrees geometry to one Fe and one P atom. In the seventh O site, O is bonded in a bent 150 degrees geometry to one Fe and one P atom. In the eighth O site, O is bonded in a distorted bent 120 degrees geometry to one Fe and one P atom. In the ninth O site, O is bonded in a bent 150 degrees geometry to one Fe and one P atom. In the tenth O site, O is bonded in a 2-coordinate geometry to two Fe and one P atom. In the eleventh O site, O is bonded in a bent 150 degrees geometry to one Fe and one P atom. In the twelfth O site, O is bonded in a bent 150 degrees geometry to one Fe and one P atom. In the thirteenth O site, O is bonded in a bent 150 degrees geometry to one Fe and one P atom. In the fourteenth O site, O is bonded in a distorted bent 120 degrees geometry to one Fe and one P atom. In the fifteenth O site, O is bonded in a bent 150 degrees geometry to one Fe and one P atom. In the sixteenth O site, O is bonded in a bent 120 degrees geometry to two P atoms. In the seventeenth O site, O is bonded in a distorted bent 120 degrees geometry to one Fe and one P atom. In the eighteenth O site, O is bonded in a bent 120 degrees geometry to two P atoms. In the nineteenth O site, O is bonded in a distorted bent 120 degrees geometry to two P atoms. In the twentieth O site, O is bonded in a distorted bent 150 degrees geometry to one Fe and one P atom. In the twenty-first O site, O is bonded in a bent 150 degrees geometry to one Fe and one P atom. In the twenty-second O site, O is bonded in a water-like geometry to one Fe and one P atom. In the twenty-third O site, O is bonded in a bent 150 degrees geometry to one Fe and one P atom. In the twenty-fourth O site, O is bonded in a bent 150 degrees geometry to one Fe and one P atom. In the twenty-fifth O site, O is bonded in a water-like geometry to one Fe and one P atom. In the twenty-sixth O site, O is bonded in a single-bond geometry to one P atom. In the twenty-seventh O site, O is bonded in a bent 150 degrees geometry to one Fe and one P atom. In the twenty-eighth O site, O is bonded in a single-bond geometry to one P atom.