Materials Data on CaFe2(AsO5)2 by Materials Project
CaFe2(AsO5)2 crystallizes in the orthorhombic Cccm space group. The structure is three-dimensional. there are two inequivalent Ca sites. In the first Ca site, Ca is bonded in a 8-coordinate geometry to eight O atoms. There are four shorter (2.39 Å) and four longer (2.80 Å) Ca–O bond lengths. In the second Ca site, Ca is bonded to six O atoms to form CaO6 octahedra that share corners with four equivalent FeO6 octahedra and corners with six AsO4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. There are two shorter (2.33 Å) and four longer (2.44 Å) Ca–O bond lengths. Fe is bonded to six O atoms to form FeO6 octahedra that share a cornercorner with one CaO6 octahedra, a cornercorner with one FeO6 octahedra, corners with four AsO4 tetrahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 47–58°. There are a spread of Fe–O bond distances ranging from 1.91–2.10 Å. There are two inequivalent As sites. In the first As site, As is bonded to four O atoms to form AsO4 tetrahedra that share a cornercorner with one CaO6 octahedra and corners with four equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 49–66°. There are a spread of As–O bond distances ranging from 1.67–1.76 Å. In the second As site, As is bonded to four O atoms to form AsO4 tetrahedra that share corners with two equivalent CaO6 octahedra and corners with four equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 42–62°. There is two shorter (1.71 Å) and two longer (1.73 Å) As–O bond length. There are seven inequivalent O sites. In the first O site, O is bonded in a trigonal planar geometry to one Ca, one Fe, and one As atom. In the second O site, O is bonded in a trigonal planar geometry to one Ca, one Fe, and one As atom. In the third O site, O is bonded in a water-like geometry to two equivalent Fe atoms. In the fourth O site, O is bonded in a bent 120 degrees geometry to two equivalent Fe atoms. In the fifth O site, O is bonded in a distorted trigonal planar geometry to two equivalent Fe and one As atom. In the sixth O site, O is bonded in a bent 120 degrees geometry to one Ca and one As atom. In the seventh O site, O is bonded in a 2-coordinate geometry to one Ca, one Fe, and one As atom.