Materials Data on Rb2Fe2As2O9 by Materials Project
Rb2Fe2As2O9 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Rb–O bond distances ranging from 2.75–3.27 Å. In the second Rb1+ site, Rb1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Rb–O bond distances ranging from 2.98–3.14 Å. There are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with five AsO4 tetrahedra and edges with two equivalent FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.94–2.24 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four AsO4 tetrahedra and edges with four FeO6 octahedra. There are two shorter (1.96 Å) and four longer (2.07 Å) Fe–O bond lengths. There are two inequivalent As5+ sites. In the first As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with four FeO6 octahedra. The corner-sharing octahedra tilt angles range from 50–53°. There are a spread of As–O bond distances ranging from 1.68–1.77 Å. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with five FeO6 octahedra. The corner-sharing octahedra tilt angles range from 40–58°. There are a spread of As–O bond distances ranging from 1.69–1.75 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Rb1+, two Fe3+, and one As5+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Rb1+, one Fe3+, and one As5+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Rb1+, one Fe3+, and one As5+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to four Rb1+ and one As5+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Rb1+ and three Fe3+ atoms. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to three Rb1+ and one As5+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Fe3+ and one As5+ atom.