Ba2SrI6 is Hydrophilite-derived structured and crystallizes in the tetragonal P4_2/mnm space group. Ba(1) is bonded to two equivalent I(1) and four equivalent I(2) atoms to form BaI6 octahedra that share corners with four equivalent Ba(1)I6 octahedra, corners with four equivalent Sr(1)I6 octahedra,  an edgeedge with one Ba(1)I6 octahedra, and  an edgeedge with one Sr(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 47-53°. Sr(1) is bonded to two equivalent I(1) and four equivalent I(2) atoms to form SrI6 octahedra that share corners with eight equivalent Ba(1)I6 octahedra and edges with two equivalent Ba(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 47-48°. There are two inequivalent I sites. In the first I site, I(1) is bonded in a distorted trigonal planar geometry to two equivalent Ba(1) and one Sr(1) atom. In the second I site, I(2) is bonded in a trigonal planar geometry to two equivalent Ba(1) and one Sr(1) atom.
Ba2SrI6 is Hydrophilite-derived structured and crystallizes in the tetragonal P4_2/mnm space group. Ba(1) is bonded to two equivalent I(1) and four equivalent I(2) atoms to form BaI6 octahedra that share corners with four equivalent Ba(1)I6 octahedra, corners with four equivalent Sr(1)I6 octahedra,  an edgeedge with one Ba(1)I6 octahedra, and  an edgeedge with one Sr(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 47-53°. Both Ba(1)-I(1) bond lengths are 3.49 Å. All Ba(1)-I(2) bond lengths are 3.48 Å. Sr(1) is bonded to two equivalent I(1) and four equivalent I(2) atoms to form SrI6 octahedra that share corners with eight equivalent Ba(1)I6 octahedra and edges with two equivalent Ba(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 47-48°. Both Sr(1)-I(1) bond lengths are 3.33 Å. All Sr(1)-I(2) bond lengths are 3.31 Å. There are two inequivalent I sites. In the first I site, I(1) is bonded in a distorted trigonal planar geometry to two equivalent Ba(1) and one Sr(1) atom. In the second I site, I(2) is bonded in a trigonal planar geometry to two equivalent Ba(1) and one Sr(1) atom.