TmF3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. Tm(1) is bonded in a distorted body-centered cubic geometry to six equivalent F(2) and eight equivalent F(1) atoms. There are two inequivalent F sites. In the first F site, F(1) is bonded to four equivalent Tm(1) atoms to form FTm4 tetrahedra that share corners with twelve equivalent F(2)Tm6 octahedra, corners with sixteen equivalent F(1)Tm4 tetrahedra, edges with six equivalent F(1)Tm4 tetrahedra, and faces with four equivalent F(2)Tm6 octahedra. The corner-sharing octahedral tilt angles are 55°. In the second F site, F(2) is bonded to six equivalent Tm(1) atoms to form FTm6 octahedra that share corners with six equivalent F(2)Tm6 octahedra, corners with twenty-four equivalent F(1)Tm4 tetrahedra, edges with twelve equivalent F(2)Tm6 octahedra, and faces with eight equivalent F(1)Tm4 tetrahedra. The corner-sharing octahedra are not tilted.
TmF3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. Tm(1) is bonded in a distorted body-centered cubic geometry to six equivalent F(2) and eight equivalent F(1) atoms. All Tm(1)-F(2) bond lengths are 2.71 Å. All Tm(1)-F(1) bond lengths are 2.35 Å. There are two inequivalent F sites. In the first F site, F(1) is bonded to four equivalent Tm(1) atoms to form FTm4 tetrahedra that share corners with twelve equivalent F(2)Tm6 octahedra, corners with sixteen equivalent F(1)Tm4 tetrahedra, edges with six equivalent F(1)Tm4 tetrahedra, and faces with four equivalent F(2)Tm6 octahedra. The corner-sharing octahedral tilt angles are 55°. In the second F site, F(2) is bonded to six equivalent Tm(1) atoms to form FTm6 octahedra that share corners with six equivalent F(2)Tm6 octahedra, corners with twenty-four equivalent F(1)Tm4 tetrahedra, edges with twelve equivalent F(2)Tm6 octahedra, and faces with eight equivalent F(1)Tm4 tetrahedra. The corner-sharing octahedra are not tilted.