RbFe(SeO4)2 crystallizes in the trigonal P321 space group. Rb(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form distorted RbO12 cuboctahedra that share edges with six equivalent Rb(1)O12 cuboctahedra, edges with six equivalent Se(1)O4 tetrahedra, and faces with two equivalent Fe(1)O6 octahedra. Fe(1) is bonded to six equivalent O(2) atoms to form distorted FeO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra and faces with two equivalent Rb(1)O12 cuboctahedra. Se(1) is bonded to one O(1) and three equivalent O(2) atoms to form SeO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and edges with three equivalent Rb(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 34°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Rb(1) and one Se(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Rb(1), one Fe(1), and one Se(1) atom.
RbFe(SeO4)2 crystallizes in the trigonal P321 space group. Rb(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form distorted RbO12 cuboctahedra that share edges with six equivalent Rb(1)O12 cuboctahedra, edges with six equivalent Se(1)O4 tetrahedra, and faces with two equivalent Fe(1)O6 octahedra. All Rb(1)-O(1) bond lengths are 3.19 Å. All Rb(1)-O(2) bond lengths are 3.51 Å. Fe(1) is bonded to six equivalent O(2) atoms to form distorted FeO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra and faces with two equivalent Rb(1)O12 cuboctahedra. All Fe(1)-O(2) bond lengths are 2.03 Å. Se(1) is bonded to one O(1) and three equivalent O(2) atoms to form SeO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra and edges with three equivalent Rb(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 34°. The Se(1)-O(1) bond length is 1.65 Å. All Se(1)-O(2) bond lengths are 1.68 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Rb(1) and one Se(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Rb(1), one Fe(1), and one Se(1) atom.