KTmI3 crystallizes in the orthorhombic Cmcm space group. K(1) is bonded in a 8-coordinate geometry to two equivalent I(2) and six equivalent I(1) atoms. Tm(1) is bonded to two equivalent I(2) and four equivalent I(1) atoms to form a mixture of edge and corner-sharing TmI6 octahedra. The corner-sharing octahedral tilt angles are 40°. There are two inequivalent I sites. In the first I site, I(1) is bonded in a 5-coordinate geometry to three equivalent K(1) and two equivalent Tm(1) atoms. In the second I site, I(2) is bonded to two equivalent K(1) and two equivalent Tm(1) atoms to form distorted corner-sharing IK2Tm2 tetrahedra.
KTmI3 crystallizes in the orthorhombic Cmcm space group. K(1) is bonded in a 8-coordinate geometry to two equivalent I(2) and six equivalent I(1) atoms. Both K(1)-I(2) bond lengths are 3.60 Å. There are four shorter (3.60 Å) and two longer (3.96 Å) K(1)-I(1) bond lengths. Tm(1) is bonded to two equivalent I(2) and four equivalent I(1) atoms to form a mixture of edge and corner-sharing TmI6 octahedra. The corner-sharing octahedral tilt angles are 40°. Both Tm(1)-I(2) bond lengths are 3.07 Å. All Tm(1)-I(1) bond lengths are 3.06 Å. There are two inequivalent I sites. In the first I site, I(1) is bonded in a 5-coordinate geometry to three equivalent K(1) and two equivalent Tm(1) atoms. In the second I site, I(2) is bonded to two equivalent K(1) and two equivalent Tm(1) atoms to form distorted corner-sharing IK2Tm2 tetrahedra.