Rb2Ge2Se5 crystallizes in the monoclinic C2/c space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 7-coordinate geometry to one Se(1), one Se(4), one Se(6), two equivalent Se(2), and two equivalent Se(3) atoms. In the second Rb site, Rb(2) is bonded in a 6-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(5), and two equivalent Se(4) atoms. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(6) atom to form corner-sharing GeSe4 tetrahedra. In the second Ge site, Ge(2) is bonded to one Se(1), one Se(2), one Se(4), and one Se(5) atom to form corner-sharing GeSe4 tetrahedra. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted water-like geometry to one Rb(1), one Rb(2), one Ge(1), and one Ge(2) atom. In the second Se site, Se(2) is bonded to one Rb(2), two equivalent Rb(1), one Ge(1), and one Ge(2) atom to form distorted SeRb3Ge2 trigonal bipyramids that share corners with four equivalent Se(3)Rb3Ge trigonal pyramids,  an edgeedge with one Se(2)Rb3Ge2 trigonal bipyramid, and  an edgeedge with one Se(3)Rb3Ge trigonal pyramid. In the third Se site, Se(3) is bonded to one Rb(2), two equivalent Rb(1), and one Ge(1) atom to form distorted SeRb3Ge trigonal pyramids that share corners with four equivalent Se(2)Rb3Ge2 trigonal bipyramids, corners with two equivalent Se(3)Rb3Ge trigonal pyramids, and  an edgeedge with one Se(2)Rb3Ge2 trigonal bipyramid. In the fourth Se site, Se(4) is bonded in a 4-coordinate geometry to one Rb(1), two equivalent Rb(2), and one Ge(2) atom. In the fifth Se site, Se(5) is bonded in a 4-coordinate geometry to two equivalent Rb(2) and two equivalent Ge(2) atoms. In the sixth Se site, Se(6) is bonded in a distorted water-like geometry to two equivalent Rb(1) and two equivalent Ge(1) atoms.
Rb2Ge2Se5 crystallizes in the monoclinic C2/c space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 7-coordinate geometry to one Se(1), one Se(4), one Se(6), two equivalent Se(2), and two equivalent Se(3) atoms. The Rb(1)-Se(1) bond length is 3.82 Å. The Rb(1)-Se(4) bond length is 3.50 Å. The Rb(1)-Se(6) bond length is 3.87 Å. There is one shorter (3.58 Å) and one longer (3.66 Å) Rb(1)-Se(2) bond length. There is one shorter (3.46 Å) and one longer (3.57 Å) Rb(1)-Se(3) bond length. In the second Rb site, Rb(2) is bonded in a 6-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(5), and two equivalent Se(4) atoms. The Rb(2)-Se(1) bond length is 3.82 Å. The Rb(2)-Se(2) bond length is 3.66 Å. The Rb(2)-Se(3) bond length is 3.49 Å. The Rb(2)-Se(5) bond length is 3.64 Å. There is one shorter (3.45 Å) and one longer (3.54 Å) Rb(2)-Se(4) bond length. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(6) atom to form corner-sharing GeSe4 tetrahedra. The Ge(1)-Se(1) bond length is 2.40 Å. The Ge(1)-Se(2) bond length is 2.40 Å. The Ge(1)-Se(3) bond length is 2.26 Å. The Ge(1)-Se(6) bond length is 2.38 Å. In the second Ge site, Ge(2) is bonded to one Se(1), one Se(2), one Se(4), and one Se(5) atom to form corner-sharing GeSe4 tetrahedra. The Ge(2)-Se(1) bond length is 2.37 Å. The Ge(2)-Se(2) bond length is 2.39 Å. The Ge(2)-Se(4) bond length is 2.26 Å. The Ge(2)-Se(5) bond length is 2.39 Å. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted water-like geometry to one Rb(1), one Rb(2), one Ge(1), and one Ge(2) atom. In the second Se site, Se(2) is bonded to one Rb(2), two equivalent Rb(1), one Ge(1), and one Ge(2) atom to form distorted SeRb3Ge2 trigonal bipyramids that share corners with four equivalent Se(3)Rb3Ge trigonal pyramids,  an edgeedge with one Se(2)Rb3Ge2 trigonal bipyramid, and  an edgeedge with one Se(3)Rb3Ge trigonal pyramid. In the third Se site, Se(3) is bonded to one Rb(2), two equivalent Rb(1), and one Ge(1) atom to form distorted SeRb3Ge trigonal pyramids that share corners with four equivalent Se(2)Rb3Ge2 trigonal bipyramids, corners with two equivalent Se(3)Rb3Ge trigonal pyramids, and  an edgeedge with one Se(2)Rb3Ge2 trigonal bipyramid. In the fourth Se site, Se(4) is bonded in a 4-coordinate geometry to one Rb(1), two equivalent Rb(2), and one Ge(2) atom. In the fifth Se site, Se(5) is bonded in a 4-coordinate geometry to two equivalent Rb(2) and two equivalent Ge(2) atoms. In the sixth Se site, Se(6) is bonded in a distorted water-like geometry to two equivalent Rb(1) and two equivalent Ge(1) atoms.