Sr2CaI6 is Hydrophilite-derived structured and crystallizes in the monoclinic C2/c space group. Sr(1) is bonded to one I(1), two equivalent I(2), and three equivalent I(3) atoms to form SrI6 octahedra that share corners with six equivalent Sr(1)I6 octahedra, corners with two equivalent Ca(1)I6 pentagonal pyramids,  an edgeedge with one Sr(1)I6 octahedra, and  an edgeedge with one Ca(1)I6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 52-69°. Ca(1) is bonded to two equivalent I(2) and four equivalent I(1) atoms to form distorted CaI6 pentagonal pyramids that share corners with four equivalent Sr(1)I6 octahedra, edges with two equivalent Sr(1)I6 octahedra, and edges with two equivalent Ca(1)I6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 42-56°. There are three inequivalent I sites. In the first I site, I(1) is bonded in a trigonal non-coplanar geometry to one Sr(1) and two equivalent Ca(1) atoms. In the second I site, I(2) is bonded in a trigonal non-coplanar geometry to two equivalent Sr(1) and one Ca(1) atom. In the third I site, I(3) is bonded in a trigonal planar geometry to three equivalent Sr(1) atoms.
Sr2CaI6 is Hydrophilite-derived structured and crystallizes in the monoclinic C2/c space group. Sr(1) is bonded to one I(1), two equivalent I(2), and three equivalent I(3) atoms to form SrI6 octahedra that share corners with six equivalent Sr(1)I6 octahedra, corners with two equivalent Ca(1)I6 pentagonal pyramids,  an edgeedge with one Sr(1)I6 octahedra, and  an edgeedge with one Ca(1)I6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 52-69°. The Sr(1)-I(1) bond length is 3.26 Å. There is one shorter (3.33 Å) and one longer (3.40 Å) Sr(1)-I(2) bond length. There are a spread of Sr(1)-I(3) bond distances ranging from 3.28-3.47 Å. Ca(1) is bonded to two equivalent I(2) and four equivalent I(1) atoms to form distorted CaI6 pentagonal pyramids that share corners with four equivalent Sr(1)I6 octahedra, edges with two equivalent Sr(1)I6 octahedra, and edges with two equivalent Ca(1)I6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 42-56°. Both Ca(1)-I(2) bond lengths are 3.24 Å. All Ca(1)-I(1) bond lengths are 3.18 Å. There are three inequivalent I sites. In the first I site, I(1) is bonded in a trigonal non-coplanar geometry to one Sr(1) and two equivalent Ca(1) atoms. In the second I site, I(2) is bonded in a trigonal non-coplanar geometry to two equivalent Sr(1) and one Ca(1) atom. In the third I site, I(3) is bonded in a trigonal planar geometry to three equivalent Sr(1) atoms.