Cs2SiS3 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 S(1), two equivalent S(3), and three equivalent S(2) atoms to form distorted CsS7 pentagonal bipyramids that share corners with two equivalent Cs(1)S7 pentagonal bipyramids, corners with three equivalent Si(1)S4 tetrahedra, edges with four equivalent Cs(1)S7 pentagonal bipyramids, and edges with three equivalent Si(1)S4 tetrahedra. In the second Cs site, Cs(2) is bonded in a 7-coordinate geometry to two equivalent S(1), two equivalent S(2), and three equivalent S(3) atoms. Si(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form SiS4 tetrahedra that share corners with three equivalent Cs(1)S7 pentagonal bipyramids, edges with three equivalent Cs(1)S7 pentagonal bipyramids, and  an edgeedge with one Si(1)S4 tetrahedra. There are three inequivalent S sites. In the first S site, S(1) is bonded in a distorted L-shaped geometry to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Si(1) atoms. In the second S site, S(2) is bonded to two equivalent Cs(2), three equivalent Cs(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing SCs5Si octahedra. The corner-sharing octahedral tilt angles range from 1-84°. In the third S site, S(3) is bonded to two equivalent Cs(1), three equivalent Cs(2), and one Si(1) atom to form a mixture of distorted corner and edge-sharing SCs5Si octahedra. The corner-sharing octahedral tilt angles range from 1-84°.
Cs2SiS3 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 S(1), two equivalent S(3), and three equivalent S(2) atoms to form distorted CsS7 pentagonal bipyramids that share corners with two equivalent Cs(1)S7 pentagonal bipyramids, corners with three equivalent Si(1)S4 tetrahedra, edges with four equivalent Cs(1)S7 pentagonal bipyramids, and edges with three equivalent Si(1)S4 tetrahedra. Both Cs(1)-S(1) bond lengths are 3.67 Å. There is one shorter (3.48 Å) and one longer (3.51 Å) Cs(1)-S(3) bond length. There is one shorter (3.51 Å) and two longer (3.62 Å) Cs(1)-S(2) bond lengths. In the second Cs site, Cs(2) is bonded in a 7-coordinate geometry to two equivalent S(1), two equivalent S(2), and three equivalent S(3) atoms. Both Cs(2)-S(1) bond lengths are 3.96 Å. There is one shorter (3.51 Å) and one longer (3.77 Å) Cs(2)-S(2) bond length. There is one shorter (3.53 Å) and two longer (3.65 Å) Cs(2)-S(3) bond lengths. Si(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form SiS4 tetrahedra that share corners with three equivalent Cs(1)S7 pentagonal bipyramids, edges with three equivalent Cs(1)S7 pentagonal bipyramids, and  an edgeedge with one Si(1)S4 tetrahedra. The Si(1)-S(2) bond length is 2.07 Å. The Si(1)-S(3) bond length is 2.08 Å. Both Si(1)-S(1) bond lengths are 2.21 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded in a distorted L-shaped geometry to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Si(1) atoms. In the second S site, S(2) is bonded to two equivalent Cs(2), three equivalent Cs(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing SCs5Si octahedra. The corner-sharing octahedral tilt angles range from 1-84°. In the third S site, S(3) is bonded to two equivalent Cs(1), three equivalent Cs(2), and one Si(1) atom to form a mixture of distorted corner and edge-sharing SCs5Si octahedra. The corner-sharing octahedral tilt angles range from 1-84°.