Na3GdI6 crystallizes in the monoclinic C2 space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form NaI6 octahedra that share corners with two equivalent Na(2)I6 octahedra, edges with two equivalent Na(2)I6 octahedra, edges with three equivalent Na(3)I6 octahedra, and edges with three equivalent Gd(1)I6 octahedra. The corner-sharing octahedral tilt angles are 5°. In the second Na site, Na(2) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form NaI6 octahedra that share corners with two equivalent Na(1)I6 octahedra, corners with two equivalent Na(3)I6 octahedra, corners with two equivalent Gd(1)I6 octahedra, edges with two equivalent Na(1)I6 octahedra, edges with two equivalent Na(3)I6 octahedra, and edges with two equivalent Gd(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. In the third Na site, Na(3) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form NaI6 octahedra that share corners with two equivalent Na(2)I6 octahedra, edges with two equivalent Na(2)I6 octahedra, edges with three equivalent Na(1)I6 octahedra, and edges with three equivalent Gd(1)I6 octahedra. The corner-sharing octahedral tilt angles are 5°. Gd(1) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form GdI6 octahedra that share corners with two equivalent Na(2)I6 octahedra, edges with two equivalent Na(2)I6 octahedra, edges with three equivalent Na(1)I6 octahedra, and edges with three equivalent Na(3)I6 octahedra. The corner-sharing octahedra are not tilted. There are three inequivalent I sites. In the first I site, I(1) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Na(3), and one Gd(1) atom. In the second I site, I(2) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Na(3), and one Gd(1) atom. In the third I site, I(3) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Na(3), and one Gd(1) atom.
Na3GdI6 crystallizes in the monoclinic C2 space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form NaI6 octahedra that share corners with two equivalent Na(2)I6 octahedra, edges with two equivalent Na(2)I6 octahedra, edges with three equivalent Na(3)I6 octahedra, and edges with three equivalent Gd(1)I6 octahedra. The corner-sharing octahedral tilt angles are 5°. Both Na(1)-I(1) bond lengths are 3.19 Å. Both Na(1)-I(2) bond lengths are 3.20 Å. Both Na(1)-I(3) bond lengths are 3.25 Å. In the second Na site, Na(2) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form NaI6 octahedra that share corners with two equivalent Na(1)I6 octahedra, corners with two equivalent Na(3)I6 octahedra, corners with two equivalent Gd(1)I6 octahedra, edges with two equivalent Na(1)I6 octahedra, edges with two equivalent Na(3)I6 octahedra, and edges with two equivalent Gd(1)I6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. Both Na(2)-I(1) bond lengths are 3.22 Å. Both Na(2)-I(2) bond lengths are 3.26 Å. Both Na(2)-I(3) bond lengths are 3.19 Å. In the third Na site, Na(3) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form NaI6 octahedra that share corners with two equivalent Na(2)I6 octahedra, edges with two equivalent Na(2)I6 octahedra, edges with three equivalent Na(1)I6 octahedra, and edges with three equivalent Gd(1)I6 octahedra. The corner-sharing octahedral tilt angles are 5°. Both Na(3)-I(1) bond lengths are 3.22 Å. Both Na(3)-I(2) bond lengths are 3.22 Å. Both Na(3)-I(3) bond lengths are 3.21 Å. Gd(1) is bonded to two equivalent I(1), two equivalent I(2), and two equivalent I(3) atoms to form GdI6 octahedra that share corners with two equivalent Na(2)I6 octahedra, edges with two equivalent Na(2)I6 octahedra, edges with three equivalent Na(1)I6 octahedra, and edges with three equivalent Na(3)I6 octahedra. The corner-sharing octahedra are not tilted. Both Gd(1)-I(1) bond lengths are 3.07 Å. Both Gd(1)-I(2) bond lengths are 3.08 Å. Both Gd(1)-I(3) bond lengths are 3.08 Å. There are three inequivalent I sites. In the first I site, I(1) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Na(3), and one Gd(1) atom. In the second I site, I(2) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Na(3), and one Gd(1) atom. In the third I site, I(3) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Na(3), and one Gd(1) atom.