Rb2TeSe4 crystallizes in the monoclinic C2/m space group. Rb(1) is bonded in a 9-coordinate geometry to one Te(1) and eight equivalent Se(1) atoms. Te(1) is bonded to two equivalent Rb(1) and four equivalent Se(1) atoms to form TeRb2Se4 octahedra that share corners with twelve equivalent Se(1)Rb4TeSe octahedra and edges with four equivalent Se(1)Rb4TeSe octahedra. The corner-sharing octahedral tilt angles range from 53-98°. Se(1) is bonded to four equivalent Rb(1), one Te(1), and one Se(1) atom to form distorted SeRb4TeSe octahedra that share corners with three equivalent Te(1)Rb2Se4 octahedra, corners with thirteen equivalent Se(1)Rb4TeSe octahedra,  an edgeedge with one Te(1)Rb2Se4 octahedra, edges with six equivalent Se(1)Rb4TeSe octahedra, and faces with two equivalent Se(1)Rb4TeSe octahedra. The corner-sharing octahedral tilt angles range from 0-98°.
Rb2TeSe4 crystallizes in the monoclinic C2/m space group. Rb(1) is bonded in a 9-coordinate geometry to one Te(1) and eight equivalent Se(1) atoms. The Rb(1)-Te(1) bond length is 3.81 Å. There are a spread of Rb(1)-Se(1) bond distances ranging from 3.52-3.72 Å. Te(1) is bonded to two equivalent Rb(1) and four equivalent Se(1) atoms to form TeRb2Se4 octahedra that share corners with twelve equivalent Se(1)Rb4TeSe octahedra and edges with four equivalent Se(1)Rb4TeSe octahedra. The corner-sharing octahedral tilt angles range from 53-98°. All Te(1)-Se(1) bond lengths are 2.84 Å. Se(1) is bonded to four equivalent Rb(1), one Te(1), and one Se(1) atom to form distorted SeRb4TeSe octahedra that share corners with three equivalent Te(1)Rb2Se4 octahedra, corners with thirteen equivalent Se(1)Rb4TeSe octahedra,  an edgeedge with one Te(1)Rb2Se4 octahedra, edges with six equivalent Se(1)Rb4TeSe octahedra, and faces with two equivalent Se(1)Rb4TeSe octahedra. The corner-sharing octahedral tilt angles range from 0-98°. The Se(1)-Se(1) bond length is 2.38 Å.