Rb2Si2Se5 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(2), one Se(4), one Se(6), two equivalent Se(1), and two equivalent Se(5) 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 Si sites. In the first Si site, Si(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form corner-sharing SiSe4 tetrahedra. In the second Si site, Si(2) is bonded to one Se(1), one Se(2), one Se(5), and one Se(6) atom to form corner-sharing SiSe4 tetrahedra. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to one Rb(2), two equivalent Rb(1), one Si(1), and one Si(2) atom. In the second Se site, Se(2) is bonded in a distorted water-like geometry to one Rb(1), one Rb(2), one Si(1), and one Si(2) atom. In the third Se site, Se(3) is bonded in a distorted water-like geometry to two equivalent Rb(2) and two equivalent Si(1) atoms. In the fourth Se site, Se(4) is bonded in a 1-coordinate geometry to one Rb(1), two equivalent Rb(2), and one Si(1) atom. In the fifth Se site, Se(5) is bonded in a 1-coordinate geometry to one Rb(2), two equivalent Rb(1), and one Si(2) atom. In the sixth Se site, Se(6) is bonded in a distorted water-like geometry to two equivalent Rb(1) and two equivalent Si(2) atoms.
Rb2Si2Se5 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(2), one Se(4), one Se(6), two equivalent Se(1), and two equivalent Se(5) atoms. The Rb(1)-Se(2) bond length is 3.81 Å. The Rb(1)-Se(4) bond length is 3.50 Å. The Rb(1)-Se(6) bond length is 3.83 Å. There is one shorter (3.51 Å) and one longer (3.67 Å) Rb(1)-Se(1) bond length. There is one shorter (3.45 Å) and one longer (3.59 Å) Rb(1)-Se(5) 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 3.66 Å. The Rb(2)-Se(2) bond length is 3.79 Å. The Rb(2)-Se(3) bond length is 3.68 Å. The Rb(2)-Se(5) bond length is 3.49 Å. There is one shorter (3.45 Å) and one longer (3.53 Å) Rb(2)-Se(4) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form corner-sharing SiSe4 tetrahedra. The Si(1)-Se(1) bond length is 2.30 Å. The Si(1)-Se(2) bond length is 2.29 Å. The Si(1)-Se(3) bond length is 2.31 Å. The Si(1)-Se(4) bond length is 2.18 Å. In the second Si site, Si(2) is bonded to one Se(1), one Se(2), one Se(5), and one Se(6) atom to form corner-sharing SiSe4 tetrahedra. The Si(2)-Se(1) bond length is 2.32 Å. The Si(2)-Se(2) bond length is 2.32 Å. The Si(2)-Se(5) bond length is 2.18 Å. The Si(2)-Se(6) bond length is 2.30 Å. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to one Rb(2), two equivalent Rb(1), one Si(1), and one Si(2) atom. In the second Se site, Se(2) is bonded in a distorted water-like geometry to one Rb(1), one Rb(2), one Si(1), and one Si(2) atom. In the third Se site, Se(3) is bonded in a distorted water-like geometry to two equivalent Rb(2) and two equivalent Si(1) atoms. In the fourth Se site, Se(4) is bonded in a 1-coordinate geometry to one Rb(1), two equivalent Rb(2), and one Si(1) atom. In the fifth Se site, Se(5) is bonded in a 1-coordinate geometry to one Rb(2), two equivalent Rb(1), and one Si(2) atom. In the sixth Se site, Se(6) is bonded in a distorted water-like geometry to two equivalent Rb(1) and two equivalent Si(2) atoms.