Rb2CuBr3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to two equivalent Br(1), two equivalent Br(2), and three equivalent Br(3) atoms to form distorted RbBr7 pentagonal bipyramids that share corners with two equivalent Rb(1)Br7 pentagonal bipyramids,  a cornercorner with one Cu(1)Br4 tetrahedra, edges with four equivalent Rb(1)Br7 pentagonal bipyramids, and edges with four equivalent Cu(1)Br4 tetrahedra. In the second Rb site, Rb(2) is bonded in a 7-coordinate geometry to two equivalent Br(1), two equivalent Br(3), and three equivalent Br(2) atoms. Cu(1) is bonded to one Br(2), one Br(3), and two equivalent Br(1) atoms to form CuBr4 tetrahedra that share  a cornercorner with one Rb(1)Br7 pentagonal bipyramid, corners with two equivalent Cu(1)Br4 tetrahedra, and edges with four equivalent Rb(1)Br7 pentagonal bipyramids. There are three inequivalent Br sites. In the first Br site, Br(1) is bonded to two equivalent Rb(1), two equivalent Rb(2), and two equivalent Cu(1) atoms to form distorted BrRb4Cu2 octahedra that share corners with two equivalent Br(1)Rb4Cu2 octahedra, corners with two equivalent Br(2)Rb5Cu octahedra, corners with five equivalent Br(3)Rb5Cu octahedra, edges with two equivalent Br(1)Rb4Cu2 octahedra, edges with two equivalent Br(3)Rb5Cu octahedra, edges with five equivalent Br(2)Rb5Cu octahedra, and  a faceface with one Br(3)Rb5Cu octahedra. The corner-sharing octahedral tilt angles range from 14-61°. In the second Br site, Br(2) is bonded to two equivalent Rb(1), three equivalent Rb(2), and one Cu(1) atom to form distorted BrRb5Cu octahedra that share corners with two equivalent Br(1)Rb4Cu2 octahedra, corners with eight equivalent Br(3)Rb5Cu octahedra,  an edgeedge with one Br(3)Rb5Cu octahedra, edges with four equivalent Br(2)Rb5Cu octahedra, edges with five equivalent Br(1)Rb4Cu2 octahedra, and  a faceface with one Br(3)Rb5Cu octahedra. The corner-sharing octahedral tilt angles range from 14-59°. In the third Br site, Br(3) is bonded to two equivalent Rb(2), three equivalent Rb(1), and one Cu(1) atom to form distorted BrRb5Cu octahedra that share corners with five equivalent Br(1)Rb4Cu2 octahedra, corners with eight equivalent Br(2)Rb5Cu octahedra,  an edgeedge with one Br(2)Rb5Cu octahedra, edges with two equivalent Br(1)Rb4Cu2 octahedra, edges with four equivalent Br(3)Rb5Cu octahedra,  a faceface with one Br(1)Rb4Cu2 octahedra, and  a faceface with one Br(2)Rb5Cu octahedra. The corner-sharing octahedral tilt angles range from 26-61°.
Rb2CuBr3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to two equivalent Br(1), two equivalent Br(2), and three equivalent Br(3) atoms to form distorted RbBr7 pentagonal bipyramids that share corners with two equivalent Rb(1)Br7 pentagonal bipyramids,  a cornercorner with one Cu(1)Br4 tetrahedra, edges with four equivalent Rb(1)Br7 pentagonal bipyramids, and edges with four equivalent Cu(1)Br4 tetrahedra. There is one shorter (3.46 Å) and one longer (3.48 Å) Rb(1)-Br(1) bond length. Both Rb(1)-Br(2) bond lengths are 3.44 Å. There are two shorter (3.42 Å) and one longer (3.50 Å) Rb(1)-Br(3) bond length. In the second Rb site, Rb(2) is bonded in a 7-coordinate geometry to two equivalent Br(1), two equivalent Br(3), and three equivalent Br(2) atoms. Both Rb(2)-Br(1) bond lengths are 3.54 Å. Both Rb(2)-Br(3) bond lengths are 3.47 Å. There are two shorter (3.44 Å) and one longer (3.51 Å) Rb(2)-Br(2) bond length. Cu(1) is bonded to one Br(2), one Br(3), and two equivalent Br(1) atoms to form CuBr4 tetrahedra that share  a cornercorner with one Rb(1)Br7 pentagonal bipyramid, corners with two equivalent Cu(1)Br4 tetrahedra, and edges with four equivalent Rb(1)Br7 pentagonal bipyramids. The Cu(1)-Br(2) bond length is 2.45 Å. The Cu(1)-Br(3) bond length is 2.46 Å. Both Cu(1)-Br(1) bond lengths are 2.55 Å. There are three inequivalent Br sites. In the first Br site, Br(1) is bonded to two equivalent Rb(1), two equivalent Rb(2), and two equivalent Cu(1) atoms to form distorted BrRb4Cu2 octahedra that share corners with two equivalent Br(1)Rb4Cu2 octahedra, corners with two equivalent Br(2)Rb5Cu octahedra, corners with five equivalent Br(3)Rb5Cu octahedra, edges with two equivalent Br(1)Rb4Cu2 octahedra, edges with two equivalent Br(3)Rb5Cu octahedra, edges with five equivalent Br(2)Rb5Cu octahedra, and  a faceface with one Br(3)Rb5Cu octahedra. The corner-sharing octahedral tilt angles range from 14-61°. In the second Br site, Br(2) is bonded to two equivalent Rb(1), three equivalent Rb(2), and one Cu(1) atom to form distorted BrRb5Cu octahedra that share corners with two equivalent Br(1)Rb4Cu2 octahedra, corners with eight equivalent Br(3)Rb5Cu octahedra,  an edgeedge with one Br(3)Rb5Cu octahedra, edges with four equivalent Br(2)Rb5Cu octahedra, edges with five equivalent Br(1)Rb4Cu2 octahedra, and  a faceface with one Br(3)Rb5Cu octahedra. The corner-sharing octahedral tilt angles range from 14-59°. In the third Br site, Br(3) is bonded to two equivalent Rb(2), three equivalent Rb(1), and one Cu(1) atom to form distorted BrRb5Cu octahedra that share corners with five equivalent Br(1)Rb4Cu2 octahedra, corners with eight equivalent Br(2)Rb5Cu octahedra,  an edgeedge with one Br(2)Rb5Cu octahedra, edges with two equivalent Br(1)Rb4Cu2 octahedra, edges with four equivalent Br(3)Rb5Cu octahedra,  a faceface with one Br(1)Rb4Cu2 octahedra, and  a faceface with one Br(2)Rb5Cu octahedra. The corner-sharing octahedral tilt angles range from 26-61°.