Rb2MgO2 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the second Rb site, Rb(2) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form distorted RbO4 trigonal pyramids that share  a cornercorner with one Mg(2)O4 tetrahedra, corners with two equivalent Rb(2)O4 trigonal pyramids, and  an edgeedge with one Mg(2)O4 tetrahedra. In the third Rb site, Rb(3) is bonded in a 4-coordinate geometry to one O(1), one O(2), and two equivalent O(4) atoms. In the fourth Rb site, Rb(4) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), and two equivalent O(2) atoms. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted trigonal planar geometry to one O(1), one O(3), and one O(4) atom. In the second Mg site, Mg(2) is bonded to one O(3), one O(4), and two equivalent O(2) atoms to form distorted MgO4 tetrahedra that share  a cornercorner with one Rb(2)O4 trigonal pyramid,  an edgeedge with one Mg(2)O4 tetrahedra, and  an edgeedge with one Rb(2)O4 trigonal pyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(3), one Rb(4), two equivalent Rb(2), and one Mg(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Rb(1), one Rb(2), one Rb(3), two equivalent Rb(4), and two equivalent Mg(2) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Rb(1), one Rb(2), one Rb(4), one Mg(1), and one Mg(2) atom. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(3), one Mg(1), and one Mg(2) atom.
Rb2MgO2 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(4) atom. The Rb(1)-O(1) bond length is 2.96 Å. The Rb(1)-O(2) bond length is 2.89 Å. The Rb(1)-O(3) bond length is 2.76 Å. The Rb(1)-O(4) bond length is 3.05 Å. In the second Rb site, Rb(2) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form distorted RbO4 trigonal pyramids that share  a cornercorner with one Mg(2)O4 tetrahedra, corners with two equivalent Rb(2)O4 trigonal pyramids, and  an edgeedge with one Mg(2)O4 tetrahedra. The Rb(2)-O(2) bond length is 3.02 Å. The Rb(2)-O(3) bond length is 2.92 Å. There is one shorter (2.80 Å) and one longer (2.86 Å) Rb(2)-O(1) bond length. In the third Rb site, Rb(3) is bonded in a 4-coordinate geometry to one O(1), one O(2), and two equivalent O(4) atoms. The Rb(3)-O(1) bond length is 2.97 Å. The Rb(3)-O(2) bond length is 2.88 Å. There is one shorter (2.85 Å) and one longer (2.87 Å) Rb(3)-O(4) bond length. In the fourth Rb site, Rb(4) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), and two equivalent O(2) atoms. The Rb(4)-O(1) bond length is 3.11 Å. The Rb(4)-O(3) bond length is 3.26 Å. The Rb(4)-O(4) bond length is 2.96 Å. There is one shorter (3.08 Å) and one longer (3.41 Å) Rb(4)-O(2) bond length. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted trigonal planar geometry to one O(1), one O(3), and one O(4) atom. The Mg(1)-O(1) bond length is 1.90 Å. The Mg(1)-O(3) bond length is 1.95 Å. The Mg(1)-O(4) bond length is 1.94 Å. In the second Mg site, Mg(2) is bonded to one O(3), one O(4), and two equivalent O(2) atoms to form distorted MgO4 tetrahedra that share  a cornercorner with one Rb(2)O4 trigonal pyramid,  an edgeedge with one Mg(2)O4 tetrahedra, and  an edgeedge with one Rb(2)O4 trigonal pyramid. The Mg(2)-O(3) bond length is 2.02 Å. The Mg(2)-O(4) bond length is 2.04 Å. Both Mg(2)-O(2) bond lengths are 2.01 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(3), one Rb(4), two equivalent Rb(2), and one Mg(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Rb(1), one Rb(2), one Rb(3), two equivalent Rb(4), and two equivalent Mg(2) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Rb(1), one Rb(2), one Rb(4), one Mg(1), and one Mg(2) atom. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Rb(1), one Rb(4), two equivalent Rb(3), one Mg(1), and one Mg(2) atom.