BaCaI4 crystallizes in the monoclinic C2/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one I(3), one I(4), two equivalent I(2), and two equivalent I(5) atoms to form distorted BaI6 octahedra that share corners with two equivalent Ca(1)I6 octahedra, corners with two equivalent Ca(2)I6 octahedra,  an edgeedge with one Ca(1)I6 octahedra, edges with two equivalent Ba(2)I6 octahedra, and edges with two equivalent Ca(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 11-24°. In the second Ba site, Ba(2) is bonded to two equivalent I(1), two equivalent I(4), and two equivalent I(5) atoms to form distorted BaI6 octahedra that share corners with two equivalent Ca(1)I6 octahedra, corners with two equivalent Ca(2)I6 octahedra,  an edgeedge with one Ba(2)I6 octahedra, edges with two equivalent Ba(1)I6 octahedra, and edges with two equivalent Ca(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 10-21°. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one I(3), one I(4), two equivalent I(1), and two equivalent I(5) atoms to form CaI6 octahedra that share corners with two equivalent Ba(1)I6 octahedra, corners with two equivalent Ba(2)I6 octahedra,  an edgeedge with one Ba(1)I6 octahedra, edges with two equivalent Ba(2)I6 octahedra, and edges with two equivalent Ca(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 10-24°. In the second Ca site, Ca(2) is bonded to two equivalent I(2), two equivalent I(3), and two equivalent I(5) atoms to form CaI6 octahedra that share corners with two equivalent Ba(1)I6 octahedra, corners with two equivalent Ba(2)I6 octahedra,  an edgeedge with one Ca(2)I6 octahedra, edges with two equivalent Ba(1)I6 octahedra, and edges with two equivalent Ca(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 11-21°. There are five inequivalent I sites. In the first I site, I(1) is bonded in a linear geometry to one Ba(2) and one Ca(1) atom. In the second I site, I(2) is bonded in a linear geometry to one Ba(1) and one Ca(2) atom. In the third I site, I(3) is bonded in a distorted see-saw-like geometry to one Ba(1), one Ca(1), and two equivalent Ca(2) atoms. In the fourth I site, I(4) is bonded in a see-saw-like geometry to one Ba(1), two equivalent Ba(2), and one Ca(1) atom. In the fifth I site, I(5) is bonded in a distorted see-saw-like geometry to one Ba(1), one Ba(2), one Ca(1), and one Ca(2) atom.
BaCaI4 crystallizes in the monoclinic C2/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one I(3), one I(4), two equivalent I(2), and two equivalent I(5) atoms to form distorted BaI6 octahedra that share corners with two equivalent Ca(1)I6 octahedra, corners with two equivalent Ca(2)I6 octahedra,  an edgeedge with one Ca(1)I6 octahedra, edges with two equivalent Ba(2)I6 octahedra, and edges with two equivalent Ca(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 11-24°. The Ba(1)-I(3) bond length is 3.51 Å. The Ba(1)-I(4) bond length is 3.55 Å. Both Ba(1)-I(2) bond lengths are 3.31 Å. Both Ba(1)-I(5) bond lengths are 3.65 Å. In the second Ba site, Ba(2) is bonded to two equivalent I(1), two equivalent I(4), and two equivalent I(5) atoms to form distorted BaI6 octahedra that share corners with two equivalent Ca(1)I6 octahedra, corners with two equivalent Ca(2)I6 octahedra,  an edgeedge with one Ba(2)I6 octahedra, edges with two equivalent Ba(1)I6 octahedra, and edges with two equivalent Ca(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 10-21°. Both Ba(2)-I(1) bond lengths are 3.30 Å. Both Ba(2)-I(4) bond lengths are 3.62 Å. Both Ba(2)-I(5) bond lengths are 3.54 Å. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one I(3), one I(4), two equivalent I(1), and two equivalent I(5) atoms to form CaI6 octahedra that share corners with two equivalent Ba(1)I6 octahedra, corners with two equivalent Ba(2)I6 octahedra,  an edgeedge with one Ba(1)I6 octahedra, edges with two equivalent Ba(2)I6 octahedra, and edges with two equivalent Ca(2)I6 octahedra. The corner-sharing octahedral tilt angles range from 10-24°. The Ca(1)-I(3) bond length is 3.24 Å. The Ca(1)-I(4) bond length is 3.26 Å. Both Ca(1)-I(1) bond lengths are 2.99 Å. Both Ca(1)-I(5) bond lengths are 3.30 Å. In the second Ca site, Ca(2) is bonded to two equivalent I(2), two equivalent I(3), and two equivalent I(5) atoms to form CaI6 octahedra that share corners with two equivalent Ba(1)I6 octahedra, corners with two equivalent Ba(2)I6 octahedra,  an edgeedge with one Ca(2)I6 octahedra, edges with two equivalent Ba(1)I6 octahedra, and edges with two equivalent Ca(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 11-21°. Both Ca(2)-I(2) bond lengths are 2.99 Å. Both Ca(2)-I(3) bond lengths are 3.32 Å. Both Ca(2)-I(5) bond lengths are 3.24 Å. There are five inequivalent I sites. In the first I site, I(1) is bonded in a linear geometry to one Ba(2) and one Ca(1) atom. In the second I site, I(2) is bonded in a linear geometry to one Ba(1) and one Ca(2) atom. In the third I site, I(3) is bonded in a distorted see-saw-like geometry to one Ba(1), one Ca(1), and two equivalent Ca(2) atoms. In the fourth I site, I(4) is bonded in a see-saw-like geometry to one Ba(1), two equivalent Ba(2), and one Ca(1) atom. In the fifth I site, I(5) is bonded in a distorted see-saw-like geometry to one Ba(1), one Ba(2), one Ca(1), and one Ca(2) atom.