DOE OSTI2020
Sr2Fe(PO4)3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Sr is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Sr–O bond distances ranging from 2.50–2.92 Å. Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 2.00–2.05 Å. There are two inequivalent P sites. In the first P site, P is bonded to four O atoms to form PO4 tetrahedra that share corners with two equivalent FeO6 octahedra. The corner-sharing octahedral tilt angles are 27°. There is two shorter (1.54 Å) and two longer (1.55 Å) P–O bond length. In the second P site, P is bonded to four O atoms to form PO4 tetrahedra that share corners with two equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 38–44°. There is two shorter (1.54 Å) and two longer (1.56 Å) P–O bond length. There are six inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to one Sr, one Fe, and one P atom. In the second O site, O is bonded in a distorted bent 120 degrees geometry to one Sr and one P atom. In the third O site, O is bonded in a 1-coordinate geometry to three equivalent Sr and one P atom. In the fourth O site, O is bonded in a distorted bent 150 degrees geometry to one Sr and one P atom. In the fifth O site, O is bonded in a 2-coordinate geometry to one Sr, one Fe, and one P atom. In the sixth O site, O is bonded in a 3-coordinate geometry to one Sr, one Fe, and one P atom.