Rb3Cu5O4 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to one O(3), one O(4), and two equivalent O(1) atoms to form distorted edge-sharing RbO4 trigonal pyramids. In the second Rb site, Rb(2) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(4) atom. 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. There are five inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a linear geometry to one O(1) and one O(3) atom. In the second Cu site, Cu(2) is bonded in a linear geometry to one O(2) and one O(4) atom. In the third Cu site, Cu(3) is bonded in a linear geometry to one O(2) and one O(3) atom. In the fourth Cu site, Cu(4) is bonded in a linear geometry to one O(1) and one O(3) atom. In the fifth Cu site, Cu(5) is bonded in a linear geometry to one O(2) and one O(4) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(1), one Cu(1), and one Cu(4) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Rb(2), one Rb(3), one Cu(2), one Cu(3), and one Cu(5) atom. In the third O site, O(3) is bonded to one Rb(1), one Rb(2), one Cu(1), one Cu(3), and one Cu(4) atom to form distorted corner-sharing ORb2Cu3 square pyramids. The corner-sharing octahedral tilt angles range from 19-72°. In the fourth O site, O(4) is bonded to one Rb(1), one Rb(2), two equivalent Rb(3), one Cu(2), and one Cu(5) atom to form distorted ORb4Cu2 octahedra that share corners with two equivalent O(3)Rb2Cu3 square pyramids and  an edgeedge with one O(4)Rb4Cu2 octahedra.
Rb3Cu5O4 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to one O(3), one O(4), and two equivalent O(1) atoms to form distorted edge-sharing RbO4 trigonal pyramids. The Rb(1)-O(3) bond length is 2.81 Å. The Rb(1)-O(4) bond length is 2.92 Å. There is one shorter (2.80 Å) and one longer (2.85 Å) Rb(1)-O(1) bond length. In the second Rb site, Rb(2) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(4) atom. The Rb(2)-O(1) bond length is 2.96 Å. The Rb(2)-O(2) bond length is 2.77 Å. The Rb(2)-O(3) bond length is 2.90 Å. The Rb(2)-O(4) bond length is 2.86 Å. 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 3.21 Å. The Rb(3)-O(2) bond length is 3.20 Å. There is one shorter (2.87 Å) and one longer (2.99 Å) Rb(3)-O(4) bond length. There are five inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a linear geometry to one O(1) and one O(3) atom. The Cu(1)-O(1) bond length is 1.80 Å. The Cu(1)-O(3) bond length is 1.85 Å. In the second Cu site, Cu(2) is bonded in a linear geometry to one O(2) and one O(4) atom. The Cu(2)-O(2) bond length is 1.84 Å. The Cu(2)-O(4) bond length is 1.81 Å. In the third Cu site, Cu(3) is bonded in a linear geometry to one O(2) and one O(3) atom. The Cu(3)-O(2) bond length is 1.83 Å. The Cu(3)-O(3) bond length is 1.84 Å. In the fourth Cu site, Cu(4) is bonded in a linear geometry to one O(1) and one O(3) atom. The Cu(4)-O(1) bond length is 1.81 Å. The Cu(4)-O(3) bond length is 1.84 Å. In the fifth Cu site, Cu(5) is bonded in a linear geometry to one O(2) and one O(4) atom. The Cu(5)-O(2) bond length is 1.83 Å. The Cu(5)-O(4) bond length is 1.82 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Rb(2), one Rb(3), two equivalent Rb(1), one Cu(1), and one Cu(4) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Rb(2), one Rb(3), one Cu(2), one Cu(3), and one Cu(5) atom. In the third O site, O(3) is bonded to one Rb(1), one Rb(2), one Cu(1), one Cu(3), and one Cu(4) atom to form distorted corner-sharing ORb2Cu3 square pyramids. The corner-sharing octahedral tilt angles range from 19-72°. In the fourth O site, O(4) is bonded to one Rb(1), one Rb(2), two equivalent Rb(3), one Cu(2), and one Cu(5) atom to form distorted ORb4Cu2 octahedra that share corners with two equivalent O(3)Rb2Cu3 square pyramids and  an edgeedge with one O(4)Rb4Cu2 octahedra.