Rb3CuO2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 3-coordinate geometry to one O(2) and two equivalent O(1) atoms. In the second Rb site, Rb(2) is bonded in a 3-coordinate geometry to one O(1) and two equivalent O(2) atoms. In the third Rb site, Rb(3) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form distorted corner-sharing RbO4 tetrahedra. Cu(1) is bonded in a linear geometry to one O(1) and one O(2) atom. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Rb(2), two equivalent Rb(1), two equivalent Rb(3), and one Cu(1) atom. In the second O site, O(2) is bonded in a 1-coordinate geometry to one Rb(1), two equivalent Rb(2), two equivalent Rb(3), and one Cu(1) atom.
Rb3CuO2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 3-coordinate geometry to one O(2) and two equivalent O(1) atoms. The Rb(1)-O(2) bond length is 2.86 Å. There is one shorter (2.77 Å) and one longer (2.94 Å) Rb(1)-O(1) bond length. In the second Rb site, Rb(2) is bonded in a 3-coordinate geometry to one O(1) and two equivalent O(2) atoms. The Rb(2)-O(1) bond length is 2.89 Å. There is one shorter (2.83 Å) and one longer (3.05 Å) Rb(2)-O(2) bond length. In the third Rb site, Rb(3) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form distorted corner-sharing RbO4 tetrahedra. There is one shorter (2.89 Å) and one longer (2.90 Å) Rb(3)-O(1) bond length. There is one shorter (2.83 Å) and one longer (2.95 Å) Rb(3)-O(2) bond length. Cu(1) is bonded in a linear geometry to one O(1) and one O(2) atom. The Cu(1)-O(1) bond length is 1.80 Å. The Cu(1)-O(2) bond length is 1.80 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Rb(2), two equivalent Rb(1), two equivalent Rb(3), and one Cu(1) atom. In the second O site, O(2) is bonded in a 1-coordinate geometry to one Rb(1), two equivalent Rb(2), two equivalent Rb(3), and one Cu(1) atom.