BaSr2I6 is Baddeleyite-derived structured and crystallizes in the monoclinic P2_1/c space group. Ba(1) is bonded to one I(1), one I(2), one I(4), one I(5), one I(6), and two equivalent I(3) atoms to form distorted BaI7 pentagonal bipyramids that share corners with four equivalent Sr(2)I7 pentagonal bipyramids,  an edgeedge with one Ba(1)I7 pentagonal bipyramid, and edges with two equivalent Sr(2)I7 pentagonal bipyramids. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 6-coordinate geometry to one I(5), two equivalent I(1), two equivalent I(2), and two equivalent I(6) atoms. In the second Sr site, Sr(2) is bonded to one I(1), one I(2), one I(3), one I(5), one I(6), and two equivalent I(4) atoms to form distorted SrI7 pentagonal bipyramids that share corners with four equivalent Ba(1)I7 pentagonal bipyramids,  an edgeedge with one Sr(2)I7 pentagonal bipyramid, and edges with two equivalent Ba(1)I7 pentagonal bipyramids. There are six inequivalent I sites. In the first I site, I(1) is bonded to one Ba(1), one Sr(2), and two equivalent Sr(1) atoms to form a mixture of corner and edge-sharing IBaSr3 tetrahedra. In the second I site, I(2) is bonded in a 4-coordinate geometry to one Ba(1), one Sr(2), and two equivalent Sr(1) atoms. In the third I site, I(3) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Ba(1) and one Sr(2) atom. In the fourth I site, I(4) is bonded in a distorted trigonal non-coplanar geometry to one Ba(1) and two equivalent Sr(2) atoms. In the fifth I site, I(5) is bonded in a trigonal non-coplanar geometry to one Ba(1), one Sr(1), and one Sr(2) atom. In the sixth I site, I(6) is bonded to one Ba(1), one Sr(2), and two equivalent Sr(1) atoms to form a mixture of distorted corner and edge-sharing IBaSr3 tetrahedra.
BaSr2I6 is Baddeleyite-derived structured and crystallizes in the monoclinic P2_1/c space group. Ba(1) is bonded to one I(1), one I(2), one I(4), one I(5), one I(6), and two equivalent I(3) atoms to form distorted BaI7 pentagonal bipyramids that share corners with four equivalent Sr(2)I7 pentagonal bipyramids,  an edgeedge with one Ba(1)I7 pentagonal bipyramid, and edges with two equivalent Sr(2)I7 pentagonal bipyramids. The Ba(1)-I(1) bond length is 3.60 Å. The Ba(1)-I(2) bond length is 3.57 Å. The Ba(1)-I(4) bond length is 3.42 Å. The Ba(1)-I(5) bond length is 3.49 Å. The Ba(1)-I(6) bond length is 3.74 Å. There is one shorter (3.46 Å) and one longer (3.47 Å) Ba(1)-I(3) bond length. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 6-coordinate geometry to one I(5), two equivalent I(1), two equivalent I(2), and two equivalent I(6) atoms. The Sr(1)-I(5) bond length is 3.27 Å. There is one shorter (3.36 Å) and one longer (3.38 Å) Sr(1)-I(1) bond length. There is one shorter (3.39 Å) and one longer (4.01 Å) Sr(1)-I(2) bond length. There is one shorter (3.47 Å) and one longer (3.49 Å) Sr(1)-I(6) bond length. In the second Sr site, Sr(2) is bonded to one I(1), one I(2), one I(3), one I(5), one I(6), and two equivalent I(4) atoms to form distorted SrI7 pentagonal bipyramids that share corners with four equivalent Ba(1)I7 pentagonal bipyramids,  an edgeedge with one Sr(2)I7 pentagonal bipyramid, and edges with two equivalent Ba(1)I7 pentagonal bipyramids. The Sr(2)-I(1) bond length is 3.51 Å. The Sr(2)-I(2) bond length is 3.65 Å. The Sr(2)-I(3) bond length is 3.33 Å. The Sr(2)-I(5) bond length is 3.36 Å. The Sr(2)-I(6) bond length is 3.50 Å. There is one shorter (3.30 Å) and one longer (3.35 Å) Sr(2)-I(4) bond length. There are six inequivalent I sites. In the first I site, I(1) is bonded to one Ba(1), one Sr(2), and two equivalent Sr(1) atoms to form a mixture of corner and edge-sharing IBaSr3 tetrahedra. In the second I site, I(2) is bonded in a 4-coordinate geometry to one Ba(1), one Sr(2), and two equivalent Sr(1) atoms. In the third I site, I(3) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Ba(1) and one Sr(2) atom. In the fourth I site, I(4) is bonded in a distorted trigonal non-coplanar geometry to one Ba(1) and two equivalent Sr(2) atoms. In the fifth I site, I(5) is bonded in a trigonal non-coplanar geometry to one Ba(1), one Sr(1), and one Sr(2) atom. In the sixth I site, I(6) is bonded to one Ba(1), one Sr(2), and two equivalent Sr(1) atoms to form a mixture of distorted corner and edge-sharing IBaSr3 tetrahedra.