FeSeO5 crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form edge-sharing FeO6 octahedra. Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. There are five inequivalent O sites. In the first O site, O(1) is bonded in a trigonal non-coplanar geometry to two equivalent Fe(1) and one Se(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Fe(1) and one Se(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Fe(1) and one Se(1) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one Fe(1) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Fe(1) atom.
FeSeO5 crystallizes in the monoclinic P2_1/c space group. Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form edge-sharing FeO6 octahedra. The Fe(1)-O(2) bond length is 1.90 Å. The Fe(1)-O(3) bond length is 2.01 Å. The Fe(1)-O(4) bond length is 1.69 Å. The Fe(1)-O(5) bond length is 1.73 Å. There is one shorter (2.04 Å) and one longer (2.08 Å) Fe(1)-O(1) bond length. Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. The Se(1)-O(1) bond length is 1.82 Å. The Se(1)-O(2) bond length is 1.78 Å. The Se(1)-O(3) bond length is 1.70 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a trigonal non-coplanar geometry to two equivalent Fe(1) and one Se(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Fe(1) and one Se(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Fe(1) and one Se(1) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one Fe(1) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Fe(1) atom.