RbTi3NbO9 crystallizes in the orthorhombic Pmn2_1 space group. Rb(1) is bonded in a 10-coordinate geometry to two equivalent O(3), two equivalent O(4), two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 6-coordinate geometry to one O(2), one O(3), one O(6), one O(9), and two equivalent O(1) atoms. In the second Ti site, Ti(2) is bonded in a 6-coordinate geometry to one O(1), one O(4), one O(7), one O(8), and two equivalent O(2) atoms. In the third Ti site, Ti(3) is bonded to one O(1), one O(4), one O(5), one O(7), and two equivalent O(9) atoms to form TiO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra and corners with two equivalent Ti(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 22-27°. Nb(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(8) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Ti(3)O6 octahedra and corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-29°. There are nine inequivalent O sites. In the first O site, O(1) is bonded to one Ti(2), one Ti(3), and two equivalent Ti(1) atoms to form distorted OTi4 trigonal pyramids that share corners with two equivalent O(1)Ti4 trigonal pyramids and edges with two equivalent O(2)Ti3Nb trigonal pyramids. In the second O site, O(2) is bonded to one Ti(1), two equivalent Ti(2), and one Nb(1) atom to form distorted OTi3Nb trigonal pyramids that share corners with two equivalent O(2)Ti3Nb trigonal pyramids and edges with two equivalent O(1)Ti4 trigonal pyramids. In the third O site, O(3) is bonded in a distorted linear geometry to two equivalent Rb(1), one Ti(1), and one Nb(1) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to two equivalent Rb(1), one Ti(2), and one Ti(3) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to two equivalent Rb(1), one Ti(3), and one Nb(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to two equivalent Rb(1), one Ti(1), and one Nb(1) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to two equivalent Rb(1), one Ti(2), and one Ti(3) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ti(2) and two equivalent Nb(1) atoms. In the ninth O site, O(9) is bonded in a T-shaped geometry to one Ti(1) and two equivalent Ti(3) atoms.
RbTi3NbO9 crystallizes in the orthorhombic Pmn2_1 space group. Rb(1) is bonded in a 10-coordinate geometry to two equivalent O(3), two equivalent O(4), two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms. Both Rb(1)-O(3) bond lengths are 3.32 Å. Both Rb(1)-O(4) bond lengths are 3.26 Å. Both Rb(1)-O(5) bond lengths are 3.15 Å. Both Rb(1)-O(6) bond lengths are 2.96 Å. Both Rb(1)-O(7) bond lengths are 2.96 Å. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 6-coordinate geometry to one O(2), one O(3), one O(6), one O(9), and two equivalent O(1) atoms. The Ti(1)-O(2) bond length is 2.35 Å. The Ti(1)-O(3) bond length is 1.78 Å. The Ti(1)-O(6) bond length is 1.92 Å. The Ti(1)-O(9) bond length is 2.04 Å. Both Ti(1)-O(1) bond lengths are 1.99 Å. In the second Ti site, Ti(2) is bonded in a 6-coordinate geometry to one O(1), one O(4), one O(7), one O(8), and two equivalent O(2) atoms. The Ti(2)-O(1) bond length is 2.37 Å. The Ti(2)-O(4) bond length is 1.76 Å. The Ti(2)-O(7) bond length is 1.84 Å. The Ti(2)-O(8) bond length is 2.20 Å. Both Ti(2)-O(2) bond lengths are 2.01 Å. In the third Ti site, Ti(3) is bonded to one O(1), one O(4), one O(5), one O(7), and two equivalent O(9) atoms to form TiO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra and corners with two equivalent Ti(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 22-27°. The Ti(3)-O(1) bond length is 2.09 Å. The Ti(3)-O(4) bond length is 2.00 Å. The Ti(3)-O(5) bond length is 1.96 Å. The Ti(3)-O(7) bond length is 1.91 Å. Both Ti(3)-O(9) bond lengths are 1.96 Å. Nb(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(8) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Ti(3)O6 octahedra and corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-29°. The Nb(1)-O(2) bond length is 2.25 Å. The Nb(1)-O(3) bond length is 2.05 Å. The Nb(1)-O(5) bond length is 1.89 Å. The Nb(1)-O(6) bond length is 1.94 Å. Both Nb(1)-O(8) bond lengths are 1.99 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded to one Ti(2), one Ti(3), and two equivalent Ti(1) atoms to form distorted OTi4 trigonal pyramids that share corners with two equivalent O(1)Ti4 trigonal pyramids and edges with two equivalent O(2)Ti3Nb trigonal pyramids. In the second O site, O(2) is bonded to one Ti(1), two equivalent Ti(2), and one Nb(1) atom to form distorted OTi3Nb trigonal pyramids that share corners with two equivalent O(2)Ti3Nb trigonal pyramids and edges with two equivalent O(1)Ti4 trigonal pyramids. In the third O site, O(3) is bonded in a distorted linear geometry to two equivalent Rb(1), one Ti(1), and one Nb(1) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to two equivalent Rb(1), one Ti(2), and one Ti(3) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to two equivalent Rb(1), one Ti(3), and one Nb(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to two equivalent Rb(1), one Ti(1), and one Nb(1) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to two equivalent Rb(1), one Ti(2), and one Ti(3) atom. In the eighth O site, O(8) is bonded in a distorted T-shaped geometry to one Ti(2) and two equivalent Nb(1) atoms. In the ninth O site, O(9) is bonded in a T-shaped geometry to one Ti(1) and two equivalent Ti(3) atoms.