Sm4OI6 crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a distorted single-bond geometry to one O(1), three equivalent I(2), and four equivalent I(1) atoms. In the second Sm site, Sm(2) is bonded in a distorted single-bond geometry to one O(1), three equivalent I(2), and six equivalent I(1) atoms. O(1) is bonded to one Sm(2) and three equivalent Sm(1) atoms to form OSm4 trigonal pyramids that share corners with six equivalent I(2)Sm4 tetrahedra and edges with three equivalent I(2)Sm4 tetrahedra. There are two inequivalent I sites. In the first I site, I(1) is bonded in a 6-coordinate geometry to two equivalent Sm(2) and four equivalent Sm(1) atoms. In the second I site, I(2) is bonded to one Sm(2) and three equivalent Sm(1) atoms to form distorted ISm4 tetrahedra that share corners with eight equivalent I(2)Sm4 tetrahedra, corners with two equivalent O(1)Sm4 trigonal pyramids, and  an edgeedge with one O(1)Sm4 trigonal pyramid.
Sm4OI6 crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a distorted single-bond geometry to one O(1), three equivalent I(2), and four equivalent I(1) atoms. The Sm(1)-O(1) bond length is 2.26 Å. There are two shorter (3.24 Å) and one longer (3.34 Å) Sm(1)-I(2) bond length. There are two shorter (3.32 Å) and two longer (3.55 Å) Sm(1)-I(1) bond lengths. In the second Sm site, Sm(2) is bonded in a distorted single-bond geometry to one O(1), three equivalent I(2), and six equivalent I(1) atoms. The Sm(2)-O(1) bond length is 2.41 Å. All Sm(2)-I(2) bond lengths are 3.44 Å. There are three shorter (3.49 Å) and three longer (3.97 Å) Sm(2)-I(1) bond lengths. O(1) is bonded to one Sm(2) and three equivalent Sm(1) atoms to form OSm4 trigonal pyramids that share corners with six equivalent I(2)Sm4 tetrahedra and edges with three equivalent I(2)Sm4 tetrahedra. There are two inequivalent I sites. In the first I site, I(1) is bonded in a 6-coordinate geometry to two equivalent Sm(2) and four equivalent Sm(1) atoms. In the second I site, I(2) is bonded to one Sm(2) and three equivalent Sm(1) atoms to form distorted ISm4 tetrahedra that share corners with eight equivalent I(2)Sm4 tetrahedra, corners with two equivalent O(1)Sm4 trigonal pyramids, and  an edgeedge with one O(1)Sm4 trigonal pyramid.