Rb4Li(Se2O7)2 crystallizes in the monoclinic C2 space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 8-coordinate geometry to one O(4), one O(6), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. In the second Rb site, Rb(2) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(1), two equivalent O(4), and two equivalent O(6) atoms. Li(1) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form LiO4 tetrahedra that share corners with two equivalent Se(1)O4 tetrahedra and corners with two equivalent Se(2)O4 tetrahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form SeO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra and  a cornercorner with one Se(1)O4 tetrahedra. In the second Se site, Se(2) is bonded to one O(2), one O(4), one O(6), and one O(8) atom to form SeO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra and  a cornercorner with one Se(2)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Rb(2) and one Se(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Rb(1), one Li(1), and one Se(2) atom. In the third O site, O(3) is bonded in a distorted water-like geometry to one Rb(2), two equivalent Rb(1), one Li(1), and one Se(1) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Rb(1), two equivalent Rb(2), and one Se(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Rb(1) and one Se(1) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Rb(1), two equivalent Rb(2), and one Se(2) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to two equivalent Se(1) atoms. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to two equivalent Se(2) atoms.
Rb4Li(Se2O7)2 crystallizes in the monoclinic C2 space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 8-coordinate geometry to one O(4), one O(6), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. The Rb(1)-O(4) bond length is 3.21 Å. The Rb(1)-O(6) bond length is 3.40 Å. There is one shorter (3.02 Å) and one longer (3.20 Å) Rb(1)-O(2) bond length. There is one shorter (3.37 Å) and one longer (3.41 Å) Rb(1)-O(3) bond length. There is one shorter (2.84 Å) and one longer (2.89 Å) Rb(1)-O(5) bond length. In the second Rb site, Rb(2) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(1), two equivalent O(4), and two equivalent O(6) atoms. The Rb(2)-O(3) bond length is 3.16 Å. Both Rb(2)-O(1) bond lengths are 2.81 Å. There is one shorter (3.06 Å) and one longer (3.31 Å) Rb(2)-O(4) bond length. There is one shorter (3.03 Å) and one longer (3.44 Å) Rb(2)-O(6) bond length. Li(1) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form LiO4 tetrahedra that share corners with two equivalent Se(1)O4 tetrahedra and corners with two equivalent Se(2)O4 tetrahedra. Both Li(1)-O(2) bond lengths are 2.10 Å. Both Li(1)-O(3) bond lengths are 2.01 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form SeO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra and  a cornercorner with one Se(1)O4 tetrahedra. The Se(1)-O(1) bond length is 1.66 Å. The Se(1)-O(3) bond length is 1.70 Å. The Se(1)-O(5) bond length is 1.70 Å. The Se(1)-O(7) bond length is 1.94 Å. In the second Se site, Se(2) is bonded to one O(2), one O(4), one O(6), and one O(8) atom to form SeO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra and  a cornercorner with one Se(2)O4 tetrahedra. The Se(2)-O(2) bond length is 1.66 Å. The Se(2)-O(4) bond length is 1.65 Å. The Se(2)-O(6) bond length is 1.64 Å. The Se(2)-O(8) bond length is 1.86 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Rb(2) and one Se(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Rb(1), one Li(1), and one Se(2) atom. In the third O site, O(3) is bonded in a distorted water-like geometry to one Rb(2), two equivalent Rb(1), one Li(1), and one Se(1) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Rb(1), two equivalent Rb(2), and one Se(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Rb(1) and one Se(1) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Rb(1), two equivalent Rb(2), and one Se(2) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to two equivalent Se(1) atoms. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to two equivalent Se(2) atoms.