Ba2SrI6 is Hydrophilite-derived structured and crystallizes in the trigonal P321 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form BaI6 octahedra that share corners with four equivalent Sr(1)I6 octahedra, corners with six equivalent Ba(2)I6 octahedra, and  an edgeedge with one Sr(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-54°. In the second Ba site, Ba(2) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form BaI6 octahedra that share corners with two equivalent Sr(2)I6 octahedra, corners with six equivalent Ba(1)I6 octahedra, and edges with two equivalent Sr(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-58°. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to three equivalent I(2) and three equivalent I(3) atoms to form SrI6 octahedra that share corners with six equivalent Ba(1)I6 octahedra and edges with three equivalent Ba(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-54°. In the second Sr site, Sr(2) is bonded to six equivalent I(1) atoms to form SrI6 octahedra that share corners with six equivalent Ba(2)I6 octahedra and edges with three equivalent Ba(1)I6 octahedra. The corner-sharing octahedral tilt angles are 58°. There are three inequivalent I sites. In the first I site, I(1) is bonded in a trigonal planar geometry to one Ba(1), one Ba(2), and one Sr(2) atom. In the second I site, I(2) is bonded in a trigonal planar geometry to one Ba(1), one Ba(2), and one Sr(1) atom. In the third I site, I(3) is bonded in a distorted trigonal planar geometry to one Ba(1), one Ba(2), and one Sr(1) atom.
Ba2SrI6 is Hydrophilite-derived structured and crystallizes in the trigonal P321 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form BaI6 octahedra that share corners with four equivalent Sr(1)I6 octahedra, corners with six equivalent Ba(2)I6 octahedra, and  an edgeedge with one Sr(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-54°. Both Ba(1)-I(1) bond lengths are 3.49 Å. Both Ba(1)-I(2) bond lengths are 3.50 Å. Both Ba(1)-I(3) bond lengths are 3.46 Å. In the second Ba site, Ba(2) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form BaI6 octahedra that share corners with two equivalent Sr(2)I6 octahedra, corners with six equivalent Ba(1)I6 octahedra, and edges with two equivalent Sr(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-58°. Both Ba(2)-I(1) bond lengths are 3.45 Å. Both Ba(2)-I(2) bond lengths are 3.47 Å. Both Ba(2)-I(3) bond lengths are 3.49 Å. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to three equivalent I(2) and three equivalent I(3) atoms to form SrI6 octahedra that share corners with six equivalent Ba(1)I6 octahedra and edges with three equivalent Ba(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 51-54°. All Sr(1)-I(2) bond lengths are 3.29 Å. All Sr(1)-I(3) bond lengths are 3.30 Å. In the second Sr site, Sr(2) is bonded to six equivalent I(1) atoms to form SrI6 octahedra that share corners with six equivalent Ba(2)I6 octahedra and edges with three equivalent Ba(1)I6 octahedra. The corner-sharing octahedral tilt angles are 58°. All Sr(2)-I(1) bond lengths are 3.29 Å. There are three inequivalent I sites. In the first I site, I(1) is bonded in a trigonal planar geometry to one Ba(1), one Ba(2), and one Sr(2) atom. In the second I site, I(2) is bonded in a trigonal planar geometry to one Ba(1), one Ba(2), and one Sr(1) atom. In the third I site, I(3) is bonded in a distorted trigonal planar geometry to one Ba(1), one Ba(2), and one Sr(1) atom.