Cs3FeO3 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. In the second Cs site, Cs(2) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. In the third Cs site, Cs(3) is bonded in a 3-coordinate geometry to one O(3) and two equivalent O(2) atoms. Fe(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form edge-sharing FeO4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Cs(1), one Cs(2), and two equivalent Fe(1) atoms. In the second O site, O(2) is bonded in a distorted single-bond geometry to two equivalent Cs(1), two equivalent Cs(2), two equivalent Cs(3), and one Fe(1) atom. In the third O site, O(3) is bonded in a 1-coordinate geometry to one Cs(3), two equivalent Cs(1), two equivalent Cs(2), and one Fe(1) atom.
Cs3FeO3 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. The Cs(1)-O(1) bond length is 3.17 Å. There is one shorter (2.97 Å) and one longer (3.09 Å) Cs(1)-O(2) bond length. There is one shorter (2.90 Å) and one longer (3.26 Å) Cs(1)-O(3) bond length. In the second Cs site, Cs(2) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. The Cs(2)-O(1) bond length is 2.94 Å. There is one shorter (3.16 Å) and one longer (3.42 Å) Cs(2)-O(2) bond length. There is one shorter (2.91 Å) and one longer (3.17 Å) Cs(2)-O(3) bond length. In the third Cs site, Cs(3) is bonded in a 3-coordinate geometry to one O(3) and two equivalent O(2) atoms. The Cs(3)-O(3) bond length is 2.85 Å. There is one shorter (3.03 Å) and one longer (3.12 Å) Cs(3)-O(2) bond length. Fe(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form edge-sharing FeO4 tetrahedra. The Fe(1)-O(2) bond length is 1.86 Å. The Fe(1)-O(3) bond length is 1.86 Å. There is one shorter (1.96 Å) and one longer (1.97 Å) Fe(1)-O(1) bond length. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Cs(1), one Cs(2), and two equivalent Fe(1) atoms. In the second O site, O(2) is bonded in a distorted single-bond geometry to two equivalent Cs(1), two equivalent Cs(2), two equivalent Cs(3), and one Fe(1) atom. In the third O site, O(3) is bonded in a 1-coordinate geometry to one Cs(3), two equivalent Cs(1), two equivalent Cs(2), and one Fe(1) atom.