Cs2MoSe4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 9-coordinate geometry to two equivalent Se(1), three equivalent Se(2), and four equivalent Se(3) atoms. In the second Cs site, Cs(2) is bonded in a 10-coordinate geometry to two equivalent Se(1), two equivalent Se(2), and six equivalent Se(3) atoms. Mo(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), and two equivalent Se(3) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Cs(1), two equivalent Cs(2), and one Mo(1) atom to form distorted SeCs4Mo square pyramids that share  a cornercorner with one Se(2)Cs5Mo octahedra, corners with four equivalent Se(1)Cs4Mo square pyramids, and edges with five equivalent Se(2)Cs5Mo octahedra. The corner-sharing octahedral tilt angles are 16°. In the second Se site, Se(2) is bonded to two equivalent Cs(2), three equivalent Cs(1), and one Mo(1) atom to form distorted SeCs5Mo octahedra that share corners with four equivalent Se(2)Cs5Mo octahedra,  a cornercorner with one Se(1)Cs4Mo square pyramid, edges with two equivalent Se(2)Cs5Mo octahedra, and edges with five equivalent Se(1)Cs4Mo square pyramids. The corner-sharing octahedral tilt angles range from 21-71°. In the third Se site, Se(3) is bonded in a 1-coordinate geometry to two equivalent Cs(1), three equivalent Cs(2), and one Mo(1) atom.
Cs2MoSe4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 9-coordinate geometry to two equivalent Se(1), three equivalent Se(2), and four equivalent Se(3) atoms. There is one shorter (3.58 Å) and one longer (3.68 Å) Cs(1)-Se(1) bond length. There is one shorter (3.72 Å) and two longer (3.83 Å) Cs(1)-Se(2) bond lengths. There are two shorter (3.72 Å) and two longer (3.80 Å) Cs(1)-Se(3) bond lengths. In the second Cs site, Cs(2) is bonded in a 10-coordinate geometry to two equivalent Se(1), two equivalent Se(2), and six equivalent Se(3) atoms. Both Cs(2)-Se(1) bond lengths are 3.81 Å. There is one shorter (3.94 Å) and one longer (3.96 Å) Cs(2)-Se(2) bond length. There are a spread of Cs(2)-Se(3) bond distances ranging from 3.84-4.25 Å. Mo(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), and two equivalent Se(3) atoms. The Mo(1)-Se(1) bond length is 2.31 Å. The Mo(1)-Se(2) bond length is 2.33 Å. Both Mo(1)-Se(3) bond lengths are 2.31 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Cs(1), two equivalent Cs(2), and one Mo(1) atom to form distorted SeCs4Mo square pyramids that share  a cornercorner with one Se(2)Cs5Mo octahedra, corners with four equivalent Se(1)Cs4Mo square pyramids, and edges with five equivalent Se(2)Cs5Mo octahedra. The corner-sharing octahedral tilt angles are 16°. In the second Se site, Se(2) is bonded to two equivalent Cs(2), three equivalent Cs(1), and one Mo(1) atom to form distorted SeCs5Mo octahedra that share corners with four equivalent Se(2)Cs5Mo octahedra,  a cornercorner with one Se(1)Cs4Mo square pyramid, edges with two equivalent Se(2)Cs5Mo octahedra, and edges with five equivalent Se(1)Cs4Mo square pyramids. The corner-sharing octahedral tilt angles range from 21-71°. In the third Se site, Se(3) is bonded in a 1-coordinate geometry to two equivalent Cs(1), three equivalent Cs(2), and one Mo(1) atom.