Na3TmBr6 is Ilmenite-like structured and crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent Br(1), two equivalent Br(2), and two equivalent Br(3) atoms to form NaBr6 octahedra that share corners with six equivalent Tm(1)Br6 octahedra. The corner-sharing octahedral tilt angles range from 42-46°. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent Br(1), two equivalent Br(2), and two equivalent Br(3) atoms. Tm(1) is bonded to two equivalent Br(1), two equivalent Br(2), and two equivalent Br(3) atoms to form TmBr6 octahedra that share corners with six equivalent Na(1)Br6 octahedra. The corner-sharing octahedral tilt angles range from 42-46°. There are three inequivalent Br sites. In the first Br site, Br(1) is bonded to one Na(1), two equivalent Na(2), and one Tm(1) atom to form a mixture of distorted corner and edge-sharing BrNa3Tm trigonal pyramids. In the second Br site, Br(2) is bonded to one Na(1), two equivalent Na(2), and one Tm(1) atom to form a mixture of distorted corner and edge-sharing BrNa3Tm trigonal pyramids. In the third Br site, Br(3) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), and one Tm(1) atom.
Na3TmBr6 is Ilmenite-like structured and crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent Br(1), two equivalent Br(2), and two equivalent Br(3) atoms to form NaBr6 octahedra that share corners with six equivalent Tm(1)Br6 octahedra. The corner-sharing octahedral tilt angles range from 42-46°. Both Na(1)-Br(1) bond lengths are 2.92 Å. Both Na(1)-Br(2) bond lengths are 3.02 Å. Both Na(1)-Br(3) bond lengths are 2.87 Å. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent Br(1), two equivalent Br(2), and two equivalent Br(3) atoms. There is one shorter (3.05 Å) and one longer (3.23 Å) Na(2)-Br(1) bond length. Both Na(2)-Br(2) bond lengths are 2.99 Å. There is one shorter (2.96 Å) and one longer (3.40 Å) Na(2)-Br(3) bond length. Tm(1) is bonded to two equivalent Br(1), two equivalent Br(2), and two equivalent Br(3) atoms to form TmBr6 octahedra that share corners with six equivalent Na(1)Br6 octahedra. The corner-sharing octahedral tilt angles range from 42-46°. Both Tm(1)-Br(1) bond lengths are 2.76 Å. Both Tm(1)-Br(2) bond lengths are 2.77 Å. Both Tm(1)-Br(3) bond lengths are 2.74 Å. There are three inequivalent Br sites. In the first Br site, Br(1) is bonded to one Na(1), two equivalent Na(2), and one Tm(1) atom to form a mixture of distorted corner and edge-sharing BrNa3Tm trigonal pyramids. In the second Br site, Br(2) is bonded to one Na(1), two equivalent Na(2), and one Tm(1) atom to form a mixture of distorted corner and edge-sharing BrNa3Tm trigonal pyramids. In the third Br site, Br(3) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), and one Tm(1) atom.