RbNaUSi2O9 crystallizes in the triclinic P-1 space group. Rb(1) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(5), one O(6), one O(9), and two equivalent O(2) atoms. Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), and one O(9) atom. There are two inequivalent U sites. In the first U site, U(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form UO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. In the second U site, U(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(8) atoms to form UO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one U(1)O6 octahedra,  a cornercorner with one U(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-47°. In the second Si site, Si(2) is bonded to one O(3), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one U(1)O6 octahedra,  a cornercorner with one U(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-47°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Rb(1), one Na(1), and one U(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Rb(1), one Na(1), and one U(2) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Rb(1), one U(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one U(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Rb(1), one Na(1), one U(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Rb(1), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the eighth O site, O(8) is bonded in a distorted bent 120 degrees geometry to one U(2) and one Si(2) atom. In the ninth O site, O(9) is bonded in a water-like geometry to one Rb(1) and one Na(1) atom.
RbNaUSi2O9 crystallizes in the triclinic P-1 space group. Rb(1) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(5), one O(6), one O(9), and two equivalent O(2) atoms. The Rb(1)-O(1) bond length is 2.97 Å. The Rb(1)-O(3) bond length is 3.22 Å. The Rb(1)-O(5) bond length is 3.08 Å. The Rb(1)-O(6) bond length is 2.99 Å. The Rb(1)-O(9) bond length is 3.01 Å. There is one shorter (2.88 Å) and one longer (3.12 Å) Rb(1)-O(2) bond length. Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), and one O(9) atom. The Na(1)-O(1) bond length is 2.43 Å. The Na(1)-O(2) bond length is 2.56 Å. The Na(1)-O(4) bond length is 2.37 Å. The Na(1)-O(5) bond length is 2.43 Å. The Na(1)-O(7) bond length is 2.68 Å. The Na(1)-O(9) bond length is 2.44 Å. There are two inequivalent U sites. In the first U site, U(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form UO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. Both U(1)-O(1) bond lengths are 1.86 Å. Both U(1)-O(3) bond lengths are 2.27 Å. Both U(1)-O(5) bond lengths are 2.24 Å. In the second U site, U(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(8) atoms to form UO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. Both U(2)-O(2) bond lengths are 1.88 Å. Both U(2)-O(4) bond lengths are 2.23 Å. Both U(2)-O(8) bond lengths are 2.26 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one U(1)O6 octahedra,  a cornercorner with one U(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-47°. The Si(1)-O(4) bond length is 1.62 Å. The Si(1)-O(5) bond length is 1.62 Å. The Si(1)-O(6) bond length is 1.66 Å. The Si(1)-O(7) bond length is 1.66 Å. In the second Si site, Si(2) is bonded to one O(3), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one U(1)O6 octahedra,  a cornercorner with one U(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-47°. The Si(2)-O(3) bond length is 1.63 Å. The Si(2)-O(6) bond length is 1.68 Å. The Si(2)-O(7) bond length is 1.66 Å. The Si(2)-O(8) bond length is 1.63 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Rb(1), one Na(1), and one U(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Rb(1), one Na(1), and one U(2) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Rb(1), one U(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one U(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Rb(1), one Na(1), one U(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Rb(1), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the eighth O site, O(8) is bonded in a distorted bent 120 degrees geometry to one U(2) and one Si(2) atom. In the ninth O site, O(9) is bonded in a water-like geometry to one Rb(1) and one Na(1) atom.