RhSe2 is Marcasite-like structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent Rh sites. In the first Rh site, Rh(1) is bonded to one Se(3), two equivalent Se(1), and three equivalent Se(4) atoms to form RhSe6 octahedra that share corners with four equivalent Rh(2)Se6 octahedra, corners with two equivalent Se(2)Rh3Se tetrahedra, and edges with four equivalent Rh(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 56-62°. In the second Rh site, Rh(2) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form RhSe6 octahedra that share corners with four equivalent Rh(1)Se6 octahedra, corners with four equivalent Rh(2)Se6 octahedra,  a cornercorner with one Se(2)Rh3Se tetrahedra, corners with three equivalent Se(1)Rh3Se tetrahedra, and edges with two equivalent Rh(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 56-62°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Rh(2), two equivalent Rh(1), and one Se(2) atom to form distorted SeRh3Se tetrahedra that share corners with three equivalent Rh(2)Se6 octahedra, corners with two equivalent Se(1)Rh3Se tetrahedra, and corners with three equivalent Se(2)Rh3Se tetrahedra. The corner-sharing octahedral tilt angles range from 73-75°. In the second Se site, Se(2) is bonded to three equivalent Rh(2) and one Se(1) atom to form distorted SeRh3Se tetrahedra that share  a cornercorner with one Rh(2)Se6 octahedra, corners with two equivalent Rh(1)Se6 octahedra, corners with three equivalent Se(1)Rh3Se tetrahedra, and corners with six equivalent Se(2)Rh3Se tetrahedra. The corner-sharing octahedral tilt angles range from 76-81°. In the third Se site, Se(3) is bonded in a trigonal non-coplanar geometry to one Rh(1) and two equivalent Rh(2) atoms. In the fourth Se site, Se(4) is bonded in a distorted T-shaped geometry to three equivalent Rh(1) atoms.
RhSe2 is Marcasite-like structured and crystallizes in the orthorhombic Pnma space group. There are two inequivalent Rh sites. In the first Rh site, Rh(1) is bonded to one Se(3), two equivalent Se(1), and three equivalent Se(4) atoms to form RhSe6 octahedra that share corners with four equivalent Rh(2)Se6 octahedra, corners with two equivalent Se(2)Rh3Se tetrahedra, and edges with four equivalent Rh(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 56-62°. The Rh(1)-Se(3) bond length is 2.47 Å. Both Rh(1)-Se(1) bond lengths are 2.47 Å. There is one shorter (2.50 Å) and two longer (2.52 Å) Rh(1)-Se(4) bond lengths. In the second Rh site, Rh(2) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form RhSe6 octahedra that share corners with four equivalent Rh(1)Se6 octahedra, corners with four equivalent Rh(2)Se6 octahedra,  a cornercorner with one Se(2)Rh3Se tetrahedra, corners with three equivalent Se(1)Rh3Se tetrahedra, and edges with two equivalent Rh(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 56-62°. The Rh(2)-Se(1) bond length is 2.52 Å. Both Rh(2)-Se(3) bond lengths are 2.50 Å. There is one shorter (2.43 Å) and two longer (2.47 Å) Rh(2)-Se(2) bond lengths. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Rh(2), two equivalent Rh(1), and one Se(2) atom to form distorted SeRh3Se tetrahedra that share corners with three equivalent Rh(2)Se6 octahedra, corners with two equivalent Se(1)Rh3Se tetrahedra, and corners with three equivalent Se(2)Rh3Se tetrahedra. The corner-sharing octahedral tilt angles range from 73-75°. The Se(1)-Se(2) bond length is 2.52 Å. In the second Se site, Se(2) is bonded to three equivalent Rh(2) and one Se(1) atom to form distorted SeRh3Se tetrahedra that share  a cornercorner with one Rh(2)Se6 octahedra, corners with two equivalent Rh(1)Se6 octahedra, corners with three equivalent Se(1)Rh3Se tetrahedra, and corners with six equivalent Se(2)Rh3Se tetrahedra. The corner-sharing octahedral tilt angles range from 76-81°. In the third Se site, Se(3) is bonded in a trigonal non-coplanar geometry to one Rh(1) and two equivalent Rh(2) atoms. In the fourth Se site, Se(4) is bonded in a distorted T-shaped geometry to three equivalent Rh(1) atoms.