Sr2CaI6 is Hydrophilite-derived structured and crystallizes in the trigonal P321 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form SrI6 octahedra that share corners with four equivalent Ca(1)I6 octahedra, corners with six equivalent Sr(2)I6 octahedra, and  an edgeedge with one Ca(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-53°. In the second Sr site, Sr(2) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form SrI6 octahedra that share corners with two equivalent Ca(2)I6 octahedra, corners with six equivalent Sr(1)I6 octahedra, and edges with two equivalent Ca(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-56°. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to three equivalent I(2) and three equivalent I(3) atoms to form CaI6 octahedra that share corners with six equivalent Sr(1)I6 octahedra and edges with three equivalent Sr(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-53°. In the second Ca site, Ca(2) is bonded to six equivalent I(1) atoms to form CaI6 octahedra that share corners with six equivalent Sr(2)I6 octahedra and edges with three equivalent Sr(1)I6 octahedra. The corner-sharing octahedral tilt angles are 56°. There are three inequivalent I sites. In the first I site, I(1) is bonded in a trigonal planar geometry to one Sr(1), one Sr(2), and one Ca(2) atom. In the second I site, I(2) is bonded in a distorted trigonal planar geometry to one Sr(1), one Sr(2), and one Ca(1) atom. In the third I site, I(3) is bonded in a distorted trigonal planar geometry to one Sr(1), one Sr(2), and one Ca(1) atom.
Sr2CaI6 is Hydrophilite-derived structured and crystallizes in the trigonal P321 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form SrI6 octahedra that share corners with four equivalent Ca(1)I6 octahedra, corners with six equivalent Sr(2)I6 octahedra, and  an edgeedge with one Ca(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-53°. Both Sr(1)-I(1) bond lengths are 3.33 Å. Both Sr(1)-I(2) bond lengths are 3.34 Å. Both Sr(1)-I(3) bond lengths are 3.31 Å. In the second Sr site, Sr(2) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form SrI6 octahedra that share corners with two equivalent Ca(2)I6 octahedra, corners with six equivalent Sr(1)I6 octahedra, and edges with two equivalent Ca(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-56°. Both Sr(2)-I(1) bond lengths are 3.30 Å. Both Sr(2)-I(2) bond lengths are 3.30 Å. Both Sr(2)-I(3) bond lengths are 3.31 Å. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to three equivalent I(2) and three equivalent I(3) atoms to form CaI6 octahedra that share corners with six equivalent Sr(1)I6 octahedra and edges with three equivalent Sr(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-53°. All Ca(1)-I(2) bond lengths are 3.15 Å. All Ca(1)-I(3) bond lengths are 3.16 Å. In the second Ca site, Ca(2) is bonded to six equivalent I(1) atoms to form CaI6 octahedra that share corners with six equivalent Sr(2)I6 octahedra and edges with three equivalent Sr(1)I6 octahedra. The corner-sharing octahedral tilt angles are 56°. All Ca(2)-I(1) bond lengths are 3.15 Å. There are three inequivalent I sites. In the first I site, I(1) is bonded in a trigonal planar geometry to one Sr(1), one Sr(2), and one Ca(2) atom. In the second I site, I(2) is bonded in a distorted trigonal planar geometry to one Sr(1), one Sr(2), and one Ca(1) atom. In the third I site, I(3) is bonded in a distorted trigonal planar geometry to one Sr(1), one Sr(2), and one Ca(1) atom.