K3TmF6 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent K sites. In the first K site, K(1) is bonded to two equivalent F(1), two equivalent F(2), and two equivalent F(3) atoms to form KF6 octahedra that share corners with six equivalent Tm(1)F6 octahedra. The corner-sharing octahedral tilt angles range from 33-40°. In the second K site, K(2) is bonded in a 7-coordinate geometry to two equivalent F(1), two equivalent F(2), and three equivalent F(3) atoms. Tm(1) is bonded to two equivalent F(1), two equivalent F(2), and two equivalent F(3) atoms to form TmF6 octahedra that share corners with six equivalent K(1)F6 octahedra. The corner-sharing octahedral tilt angles range from 33-40°. There are three inequivalent F sites. In the first F site, F(1) is bonded in a 4-coordinate geometry to one K(1), two equivalent K(2), and one Tm(1) atom. In the second F site, F(2) is bonded in a distorted see-saw-like geometry to one K(1), two equivalent K(2), and one Tm(1) atom. In the third F site, F(3) is bonded in a 5-coordinate geometry to one K(1), three equivalent K(2), and one Tm(1) atom.
K3TmF6 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent K sites. In the first K site, K(1) is bonded to two equivalent F(1), two equivalent F(2), and two equivalent F(3) atoms to form KF6 octahedra that share corners with six equivalent Tm(1)F6 octahedra. The corner-sharing octahedral tilt angles range from 33-40°. Both K(1)-F(1) bond lengths are 2.63 Å. Both K(1)-F(2) bond lengths are 2.59 Å. Both K(1)-F(3) bond lengths are 2.56 Å. In the second K site, K(2) is bonded in a 7-coordinate geometry to two equivalent F(1), two equivalent F(2), and three equivalent F(3) atoms. There is one shorter (2.64 Å) and one longer (2.91 Å) K(2)-F(1) bond length. There is one shorter (2.62 Å) and one longer (2.66 Å) K(2)-F(2) bond length. There are a spread of K(2)-F(3) bond distances ranging from 2.64-3.09 Å. Tm(1) is bonded to two equivalent F(1), two equivalent F(2), and two equivalent F(3) atoms to form TmF6 octahedra that share corners with six equivalent K(1)F6 octahedra. The corner-sharing octahedral tilt angles range from 33-40°. Both Tm(1)-F(1) bond lengths are 2.14 Å. Both Tm(1)-F(2) bond lengths are 2.13 Å. Both Tm(1)-F(3) bond lengths are 2.13 Å. There are three inequivalent F sites. In the first F site, F(1) is bonded in a 4-coordinate geometry to one K(1), two equivalent K(2), and one Tm(1) atom. In the second F site, F(2) is bonded in a distorted see-saw-like geometry to one K(1), two equivalent K(2), and one Tm(1) atom. In the third F site, F(3) is bonded in a 5-coordinate geometry to one K(1), three equivalent K(2), and one Tm(1) atom.