FeSeO5 crystallizes in the monoclinic C2/c space group. Fe(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent Se(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. Se(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form SeO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-54°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one 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 150 degrees geometry to two equivalent Fe(1) atoms.
FeSeO5 crystallizes in the monoclinic C2/c space group. Fe(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form FeO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent Se(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. Both Fe(1)-O(1) bond lengths are 2.09 Å. Both Fe(1)-O(2) bond lengths are 2.01 Å. Both Fe(1)-O(3) bond lengths are 1.85 Å. Se(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form SeO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-54°. Both Se(1)-O(1) bond lengths are 1.67 Å. Both Se(1)-O(2) bond lengths are 1.69 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one 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 150 degrees geometry to two equivalent Fe(1) atoms.