Sr2CaI6 crystallizes in the tetragonal P-4b2 space group. 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 two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a distorted tetrahedral geometry to four equivalent I(2) atoms. In the second Ca site, Ca(2) is bonded in a square co-planar geometry to four equivalent I(1) atoms. There are three inequivalent I sites. In the first I site, I(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Sr(2) and one Ca(2) atom. In the second I site, I(2) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Sr(1) and one Ca(1) atom. In the third I site, I(3) is bonded to two equivalent Sr(1) and two equivalent Sr(2) atoms to form a mixture of edge and corner-sharing ISr4 tetrahedra.
Sr2CaI6 crystallizes in the tetragonal P-4b2 space group. 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 (3.43 Å) and two longer (3.54 Å) Sr(1)-I(2) bond lengths. There are two shorter (3.34 Å) and two longer (3.66 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 (3.42 Å) and two longer (3.57 Å) Sr(2)-I(1) bond lengths. There are two shorter (3.42 Å) and two longer (3.54 Å) Sr(2)-I(3) bond lengths. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a distorted tetrahedral geometry to four equivalent I(2) atoms. All Ca(1)-I(2) bond lengths are 3.08 Å. In the second Ca site, Ca(2) is bonded in a square co-planar geometry to four equivalent I(1) atoms. All Ca(2)-I(1) bond lengths are 3.11 Å. There are three inequivalent I sites. In the first I site, I(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Sr(2) and one Ca(2) atom. In the second I site, I(2) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Sr(1) and one Ca(1) atom. In the third I site, I(3) is bonded to two equivalent Sr(1) and two equivalent Sr(2) atoms to form a mixture of edge and corner-sharing ISr4 tetrahedra.