Rb3TmO3 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form distorted RbO4 tetrahedra that share corners with five equivalent Tm(1)O4 tetrahedra and  an edgeedge with one Rb(1)O4 tetrahedra. In the second Rb site, Rb(2) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. In the third Rb site, Rb(3) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(1), and two equivalent O(3) atoms. Tm(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form TmO4 tetrahedra that share corners with five equivalent Rb(1)O4 tetrahedra and  an edgeedge with one Tm(1)O4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 7-coordinate geometry to two equivalent Rb(1), two equivalent Rb(2), two equivalent Rb(3), and one Tm(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Rb(1), one Rb(3), two equivalent Rb(2), and two equivalent Tm(1) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Rb(1), one Rb(2), two equivalent Rb(3), and one Tm(1) atom.
Rb3TmO3 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form distorted RbO4 tetrahedra that share corners with five equivalent Tm(1)O4 tetrahedra and  an edgeedge with one Rb(1)O4 tetrahedra. The Rb(1)-O(2) bond length is 2.83 Å. The Rb(1)-O(3) bond length is 2.77 Å. There is one shorter (2.84 Å) and one longer (2.99 Å) Rb(1)-O(1) bond length. In the second Rb site, Rb(2) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. The Rb(2)-O(3) bond length is 2.96 Å. There is one shorter (2.79 Å) and one longer (3.34 Å) Rb(2)-O(1) bond length. There is one shorter (2.94 Å) and one longer (3.46 Å) Rb(2)-O(2) bond length. In the third Rb site, Rb(3) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(1), and two equivalent O(3) atoms. The Rb(3)-O(2) bond length is 2.99 Å. Both Rb(3)-O(1) bond lengths are 3.15 Å. There is one shorter (2.69 Å) and one longer (2.98 Å) Rb(3)-O(3) bond length. Tm(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form TmO4 tetrahedra that share corners with five equivalent Rb(1)O4 tetrahedra and  an edgeedge with one Tm(1)O4 tetrahedra. The Tm(1)-O(1) bond length is 2.08 Å. The Tm(1)-O(3) bond length is 2.06 Å. There is one shorter (2.14 Å) and one longer (2.16 Å) Tm(1)-O(2) bond length. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 7-coordinate geometry to two equivalent Rb(1), two equivalent Rb(2), two equivalent Rb(3), and one Tm(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Rb(1), one Rb(3), two equivalent Rb(2), and two equivalent Tm(1) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Rb(1), one Rb(2), two equivalent Rb(3), and one Tm(1) atom.