BaSr2I6 is Fluorite-derived structured and crystallizes in the tetragonal P-4b2 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a body-centered cubic geometry to eight equivalent I(2) atoms. In the second Ba site, Ba(2) is bonded in a body-centered cubic geometry to eight equivalent I(1) atoms. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a body-centered cubic geometry to four equivalent I(2) and four equivalent I(3) atoms. In the second Sr site, Sr(2) is bonded in a body-centered cubic geometry to four equivalent I(1) and four equivalent I(3) atoms. There are three inequivalent I sites. In the first I site, I(1) is bonded to two equivalent Ba(2) and two equivalent Sr(2) atoms to form IBa2Sr2 tetrahedra that share corners with six equivalent I(3)Sr4 tetrahedra, corners with ten equivalent I(1)Ba2Sr2 tetrahedra,  an edgeedge with one I(3)Sr4 tetrahedra, and edges with five equivalent I(1)Ba2Sr2 tetrahedra. In the second I site, I(2) is bonded to two equivalent Ba(1) and two equivalent Sr(1) atoms to form IBa2Sr2 tetrahedra that share corners with six equivalent I(3)Sr4 tetrahedra, corners with ten equivalent I(2)Ba2Sr2 tetrahedra,  an edgeedge with one I(3)Sr4 tetrahedra, and edges with five equivalent I(2)Ba2Sr2 tetrahedra. In the third I site, I(3) is bonded to two equivalent Sr(1) and two equivalent Sr(2) atoms to form ISr4 tetrahedra that share corners with four equivalent I(3)Sr4 tetrahedra, corners with six equivalent I(1)Ba2Sr2 tetrahedra, corners with six equivalent I(2)Ba2Sr2 tetrahedra,  an edgeedge with one I(1)Ba2Sr2 tetrahedra,  an edgeedge with one I(2)Ba2Sr2 tetrahedra, and edges with four equivalent I(3)Sr4 tetrahedra.
BaSr2I6 is Fluorite-derived structured and crystallizes in the tetragonal P-4b2 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a body-centered cubic geometry to eight equivalent I(2) atoms. There are four shorter (3.55 Å) and four longer (3.63 Å) Ba(1)-I(2) bond lengths. In the second Ba site, Ba(2) is bonded in a body-centered cubic geometry to eight equivalent I(1) atoms. There are four shorter (3.55 Å) and four longer (3.63 Å) Ba(2)-I(1) bond lengths. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a body-centered cubic geometry to four equivalent I(2) and four equivalent I(3) atoms. There are two shorter (3.41 Å) and two longer (3.62 Å) Sr(1)-I(2) bond lengths. There are two shorter (3.39 Å) and two longer (3.67 Å) Sr(1)-I(3) bond lengths. In the second Sr site, Sr(2) is bonded in a body-centered cubic geometry to four equivalent I(1) and four equivalent I(3) atoms. There are two shorter (3.41 Å) and two longer (3.64 Å) Sr(2)-I(1) bond lengths. All Sr(2)-I(3) bond lengths are 3.51 Å. There are three inequivalent I sites. In the first I site, I(1) is bonded to two equivalent Ba(2) and two equivalent Sr(2) atoms to form IBa2Sr2 tetrahedra that share corners with six equivalent I(3)Sr4 tetrahedra, corners with ten equivalent I(1)Ba2Sr2 tetrahedra,  an edgeedge with one I(3)Sr4 tetrahedra, and edges with five equivalent I(1)Ba2Sr2 tetrahedra. In the second I site, I(2) is bonded to two equivalent Ba(1) and two equivalent Sr(1) atoms to form IBa2Sr2 tetrahedra that share corners with six equivalent I(3)Sr4 tetrahedra, corners with ten equivalent I(2)Ba2Sr2 tetrahedra,  an edgeedge with one I(3)Sr4 tetrahedra, and edges with five equivalent I(2)Ba2Sr2 tetrahedra. In the third I site, I(3) is bonded to two equivalent Sr(1) and two equivalent Sr(2) atoms to form ISr4 tetrahedra that share corners with four equivalent I(3)Sr4 tetrahedra, corners with six equivalent I(1)Ba2Sr2 tetrahedra, corners with six equivalent I(2)Ba2Sr2 tetrahedra,  an edgeedge with one I(1)Ba2Sr2 tetrahedra,  an edgeedge with one I(2)Ba2Sr2 tetrahedra, and edges with four equivalent I(3)Sr4 tetrahedra.