Ca4OI6 crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a distorted single-bond geometry to one O(1), three equivalent I(1), and four equivalent I(2) atoms. In the second Ca site, Ca(2) is bonded in a distorted single-bond geometry to one O(1), three equivalent I(1), and three equivalent I(2) atoms. O(1) is bonded in a tetrahedral geometry to one Ca(2) and three equivalent Ca(1) atoms. There are two inequivalent I sites. In the first I site, I(1) is bonded in a 4-coordinate geometry to one Ca(2) and three equivalent Ca(1) atoms. In the second I site, I(2) is bonded in a 5-coordinate geometry to one Ca(2) and four equivalent Ca(1) atoms.
Ca4OI6 crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a distorted single-bond geometry to one O(1), three equivalent I(1), and four equivalent I(2) atoms. The Ca(1)-O(1) bond length is 2.31 Å. There is one shorter (3.17 Å) and two longer (3.44 Å) Ca(1)-I(1) bond lengths. There are two shorter (3.29 Å) and two longer (3.51 Å) Ca(1)-I(2) bond lengths. In the second Ca site, Ca(2) is bonded in a distorted single-bond geometry to one O(1), three equivalent I(1), and three equivalent I(2) atoms. The Ca(2)-O(1) bond length is 2.25 Å. All Ca(2)-I(1) bond lengths are 3.53 Å. All Ca(2)-I(2) bond lengths are 3.32 Å. O(1) is bonded in a tetrahedral geometry to one Ca(2) and three equivalent Ca(1) atoms. There are two inequivalent I sites. In the first I site, I(1) is bonded in a 4-coordinate geometry to one Ca(2) and three equivalent Ca(1) atoms. In the second I site, I(2) is bonded in a 5-coordinate geometry to one Ca(2) and four equivalent Ca(1) atoms.