Cs4Fe2O5 crystallizes in the monoclinic C2/c space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(3) atoms. In the second Cs site, Cs(2) is bonded in a 4-coordinate geometry to four equivalent O(3) atoms. In the third Cs site, Cs(3) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Fe(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form a mixture of edge and corner-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), two equivalent Cs(3), and two equivalent Fe(1) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to four equivalent Cs(3) and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a 7-coordinate geometry to two equivalent Cs(1), two equivalent Cs(2), two equivalent Cs(3), and one Fe(1) atom.
Cs4Fe2O5 crystallizes in the monoclinic C2/c space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(3) atoms. Both Cs(1)-O(1) bond lengths are 3.41 Å. There are two shorter (2.90 Å) and two longer (3.20 Å) Cs(1)-O(3) bond lengths. In the second Cs site, Cs(2) is bonded in a 4-coordinate geometry to four equivalent O(3) atoms. There are two shorter (3.12 Å) and two longer (3.22 Å) Cs(2)-O(3) bond lengths. In the third Cs site, Cs(3) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. There is one shorter (3.00 Å) and one longer (3.12 Å) Cs(3)-O(1) bond length. There is one shorter (3.12 Å) and one longer (3.16 Å) Cs(3)-O(2) bond length. There is one shorter (3.16 Å) and one longer (3.23 Å) Cs(3)-O(3) bond length. Fe(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form a mixture of edge and corner-sharing FeO4 tetrahedra. The Fe(1)-O(2) bond length is 1.91 Å. The Fe(1)-O(3) bond length is 1.82 Å. There is one shorter (1.94 Å) and one longer (1.95 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), two equivalent Cs(3), and two equivalent Fe(1) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to four equivalent Cs(3) and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a 7-coordinate geometry to two equivalent Cs(1), two equivalent Cs(2), two equivalent Cs(3), and one Fe(1) atom.