Rb2MoSe4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 9-coordinate geometry to two equivalent Se(3), three equivalent Se(2), and four equivalent Se(1) atoms. In the second Rb site, Rb(2) is bonded in a 8-coordinate geometry to two equivalent Se(2), two equivalent Se(3), and four equivalent Se(1) atoms. Mo(1) is bonded in a tetrahedral geometry to one Se(2), one Se(3), and two equivalent Se(1) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to two equivalent Rb(1), two equivalent Rb(2), and one Mo(1) atom. In the second Se site, Se(2) is bonded to two equivalent Rb(2), three equivalent Rb(1), and one Mo(1) atom to form distorted SeRb5Mo octahedra that share corners with four equivalent Se(2)Rb5Mo octahedra,  a cornercorner with one Se(3)Rb4Mo square pyramid, edges with two equivalent Se(2)Rb5Mo octahedra, and edges with five equivalent Se(3)Rb4Mo square pyramids. The corner-sharing octahedral tilt angles range from 21-69°. In the third Se site, Se(3) is bonded to two equivalent Rb(1), two equivalent Rb(2), and one Mo(1) atom to form distorted SeRb4Mo square pyramids that share  a cornercorner with one Se(2)Rb5Mo octahedra, corners with four equivalent Se(3)Rb4Mo square pyramids, and edges with five equivalent Se(2)Rb5Mo octahedra. The corner-sharing octahedral tilt angles are 18°.
Rb2MoSe4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 9-coordinate geometry to two equivalent Se(3), three equivalent Se(2), and four equivalent Se(1) atoms. There is one shorter (3.41 Å) and one longer (3.49 Å) Rb(1)-Se(3) bond length. There is one shorter (3.58 Å) and two longer (3.71 Å) Rb(1)-Se(2) bond lengths. There are two shorter (3.58 Å) and two longer (3.68 Å) Rb(1)-Se(1) bond lengths. In the second Rb site, Rb(2) is bonded in a 8-coordinate geometry to two equivalent Se(2), two equivalent Se(3), and four equivalent Se(1) atoms. There is one shorter (3.73 Å) and one longer (3.83 Å) Rb(2)-Se(2) bond length. Both Rb(2)-Se(3) bond lengths are 3.70 Å. There are two shorter (3.67 Å) and two longer (3.74 Å) Rb(2)-Se(1) bond lengths. Mo(1) is bonded in a tetrahedral geometry to one Se(2), one Se(3), and two equivalent Se(1) atoms. The Mo(1)-Se(2) bond length is 2.33 Å. The Mo(1)-Se(3) bond length is 2.31 Å. Both Mo(1)-Se(1) bond lengths are 2.31 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to two equivalent Rb(1), two equivalent Rb(2), and one Mo(1) atom. In the second Se site, Se(2) is bonded to two equivalent Rb(2), three equivalent Rb(1), and one Mo(1) atom to form distorted SeRb5Mo octahedra that share corners with four equivalent Se(2)Rb5Mo octahedra,  a cornercorner with one Se(3)Rb4Mo square pyramid, edges with two equivalent Se(2)Rb5Mo octahedra, and edges with five equivalent Se(3)Rb4Mo square pyramids. The corner-sharing octahedral tilt angles range from 21-69°. In the third Se site, Se(3) is bonded to two equivalent Rb(1), two equivalent Rb(2), and one Mo(1) atom to form distorted SeRb4Mo square pyramids that share  a cornercorner with one Se(2)Rb5Mo octahedra, corners with four equivalent Se(3)Rb4Mo square pyramids, and edges with five equivalent Se(2)Rb5Mo octahedra. The corner-sharing octahedral tilt angles are 18°.