Cs2GeSe3 crystallizes in the monoclinic C2/m space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to two equivalent Se(2), two equivalent Se(3), and three equivalent Se(1) atoms to form distorted CsSe7 pentagonal bipyramids that share corners with two equivalent Cs(1)Se7 pentagonal bipyramids, corners with three equivalent Ge(1)Se4 tetrahedra, edges with four equivalent Cs(1)Se7 pentagonal bipyramids, and edges with three equivalent Ge(1)Se4 tetrahedra. In the second Cs site, Cs(2) is bonded in a 7-coordinate geometry to two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms. Ge(1) is bonded to one Se(1), one Se(2), and two equivalent Se(3) atoms to form GeSe4 tetrahedra that share corners with three equivalent Cs(1)Se7 pentagonal bipyramids, edges with three equivalent Cs(1)Se7 pentagonal bipyramids, and  an edgeedge with one Ge(1)Se4 tetrahedra. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Cs(2), three equivalent Cs(1), and one Ge(1) atom to form a mixture of distorted corner and edge-sharing SeCs5Ge octahedra. The corner-sharing octahedral tilt angles range from 3-76°. In the second Se site, Se(2) is bonded to two equivalent Cs(1), three equivalent Cs(2), and one Ge(1) atom to form a mixture of distorted corner and edge-sharing SeCs5Ge octahedra. The corner-sharing octahedral tilt angles range from 3-76°. In the third Se site, Se(3) is bonded in a 6-coordinate geometry to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Ge(1) atoms.
Cs2GeSe3 crystallizes in the monoclinic C2/m space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to two equivalent Se(2), two equivalent Se(3), and three equivalent Se(1) atoms to form distorted CsSe7 pentagonal bipyramids that share corners with two equivalent Cs(1)Se7 pentagonal bipyramids, corners with three equivalent Ge(1)Se4 tetrahedra, edges with four equivalent Cs(1)Se7 pentagonal bipyramids, and edges with three equivalent Ge(1)Se4 tetrahedra. There is one shorter (3.60 Å) and one longer (3.61 Å) Cs(1)-Se(2) bond length. Both Cs(1)-Se(3) bond lengths are 3.81 Å. There is one shorter (3.65 Å) and two longer (3.77 Å) Cs(1)-Se(1) bond lengths. In the second Cs site, Cs(2) is bonded in a 7-coordinate geometry to two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms. There is one shorter (3.64 Å) and one longer (3.87 Å) Cs(2)-Se(1) bond length. Both Cs(2)-Se(3) bond lengths are 4.15 Å. There is one shorter (3.65 Å) and two longer (3.80 Å) Cs(2)-Se(2) bond lengths. Ge(1) is bonded to one Se(1), one Se(2), and two equivalent Se(3) atoms to form GeSe4 tetrahedra that share corners with three equivalent Cs(1)Se7 pentagonal bipyramids, edges with three equivalent Cs(1)Se7 pentagonal bipyramids, and  an edgeedge with one Ge(1)Se4 tetrahedra. The Ge(1)-Se(1) bond length is 2.30 Å. The Ge(1)-Se(2) bond length is 2.31 Å. Both Ge(1)-Se(3) bond lengths are 2.45 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Cs(2), three equivalent Cs(1), and one Ge(1) atom to form a mixture of distorted corner and edge-sharing SeCs5Ge octahedra. The corner-sharing octahedral tilt angles range from 3-76°. In the second Se site, Se(2) is bonded to two equivalent Cs(1), three equivalent Cs(2), and one Ge(1) atom to form a mixture of distorted corner and edge-sharing SeCs5Ge octahedra. The corner-sharing octahedral tilt angles range from 3-76°. In the third Se site, Se(3) is bonded in a 6-coordinate geometry to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Ge(1) atoms.