CsSnI3 crystallizes in the orthorhombic Pnma space group. Cs(1) is bonded in a 9-coordinate geometry to two equivalent I(1), three equivalent I(3), and four equivalent I(2) atoms. Sn(1) is bonded to one I(2), two equivalent I(3), and three equivalent I(1) atoms to form distorted edge-sharing SnI6 octahedra. There are three inequivalent I sites. In the first I site, I(1) is bonded to two equivalent Cs(1) and three equivalent Sn(1) atoms to form distorted ICs2Sn3 trigonal bipyramids that share corners with three equivalent I(2)Cs4Sn square pyramids, corners with four equivalent I(1)Cs2Sn3 trigonal bipyramids, corners with six equivalent I(3)Cs3Sn2 trigonal bipyramids, edges with four equivalent I(2)Cs4Sn square pyramids, edges with two equivalent I(1)Cs2Sn3 trigonal bipyramids, and edges with three equivalent I(3)Cs3Sn2 trigonal bipyramids. In the second I site, I(2) is bonded to four equivalent Cs(1) and one Sn(1) atom to form distorted ICs4Sn square pyramids that share corners with four equivalent I(2)Cs4Sn square pyramids, corners with three equivalent I(1)Cs2Sn3 trigonal bipyramids, corners with six equivalent I(3)Cs3Sn2 trigonal bipyramids, edges with four equivalent I(2)Cs4Sn square pyramids, edges with four equivalent I(1)Cs2Sn3 trigonal bipyramids, and edges with four equivalent I(3)Cs3Sn2 trigonal bipyramids. In the third I site, I(3) is bonded to three equivalent Cs(1) and two equivalent Sn(1) atoms to form distorted ICs3Sn2 trigonal bipyramids that share corners with six equivalent I(2)Cs4Sn square pyramids, corners with six equivalent I(1)Cs2Sn3 trigonal bipyramids, edges with four equivalent I(2)Cs4Sn square pyramids, edges with three equivalent I(1)Cs2Sn3 trigonal bipyramids, and edges with four equivalent I(3)Cs3Sn2 trigonal bipyramids.
CsSnI3 crystallizes in the orthorhombic Pnma space group. Cs(1) is bonded in a 9-coordinate geometry to two equivalent I(1), three equivalent I(3), and four equivalent I(2) atoms. There is one shorter (4.03 Å) and one longer (4.24 Å) Cs(1)-I(1) bond length. There are two shorter (3.99 Å) and one longer (4.02 Å) Cs(1)-I(3) bond length. There are two shorter (3.93 Å) and two longer (3.96 Å) Cs(1)-I(2) bond lengths. Sn(1) is bonded to one I(2), two equivalent I(3), and three equivalent I(1) atoms to form distorted edge-sharing SnI6 octahedra. The Sn(1)-I(2) bond length is 3.00 Å. Both Sn(1)-I(3) bond lengths are 3.22 Å. There are two shorter (3.24 Å) and one longer (3.48 Å) Sn(1)-I(1) bond length. There are three inequivalent I sites. In the first I site, I(1) is bonded to two equivalent Cs(1) and three equivalent Sn(1) atoms to form distorted ICs2Sn3 trigonal bipyramids that share corners with three equivalent I(2)Cs4Sn square pyramids, corners with four equivalent I(1)Cs2Sn3 trigonal bipyramids, corners with six equivalent I(3)Cs3Sn2 trigonal bipyramids, edges with four equivalent I(2)Cs4Sn square pyramids, edges with two equivalent I(1)Cs2Sn3 trigonal bipyramids, and edges with three equivalent I(3)Cs3Sn2 trigonal bipyramids. In the second I site, I(2) is bonded to four equivalent Cs(1) and one Sn(1) atom to form distorted ICs4Sn square pyramids that share corners with four equivalent I(2)Cs4Sn square pyramids, corners with three equivalent I(1)Cs2Sn3 trigonal bipyramids, corners with six equivalent I(3)Cs3Sn2 trigonal bipyramids, edges with four equivalent I(2)Cs4Sn square pyramids, edges with four equivalent I(1)Cs2Sn3 trigonal bipyramids, and edges with four equivalent I(3)Cs3Sn2 trigonal bipyramids. In the third I site, I(3) is bonded to three equivalent Cs(1) and two equivalent Sn(1) atoms to form distorted ICs3Sn2 trigonal bipyramids that share corners with six equivalent I(2)Cs4Sn square pyramids, corners with six equivalent I(1)Cs2Sn3 trigonal bipyramids, edges with four equivalent I(2)Cs4Sn square pyramids, edges with three equivalent I(1)Cs2Sn3 trigonal bipyramids, and edges with four equivalent I(3)Cs3Sn2 trigonal bipyramids.