RbNd2Br5 crystallizes in the monoclinic P2_1/c space group. Rb(1) is bonded in a 9-coordinate geometry to two equivalent Br(2), two equivalent Br(3), two equivalent Br(4), and three equivalent Br(1) atoms. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to two equivalent Br(2), two equivalent Br(3), two equivalent Br(4), and two equivalent Br(5) atoms. In the second Nd site, Nd(2) is bonded in a 7-coordinate geometry to one Br(2), one Br(3), one Br(4), two equivalent Br(1), and two equivalent Br(5) atoms. There are five inequivalent Br sites. In the first Br site, Br(1) is bonded in a 5-coordinate geometry to three equivalent Rb(1) and two equivalent Nd(2) atoms. In the second Br site, Br(2) is bonded in a 5-coordinate geometry to two equivalent Rb(1), one Nd(2), and two equivalent Nd(1) atoms. In the third Br site, Br(3) is bonded to two equivalent Rb(1), one Nd(2), and two equivalent Nd(1) atoms to form distorted BrRb2Nd3 trigonal bipyramids that share corners with four equivalent Br(4)Rb2Nd3 square pyramids, corners with two equivalent Br(5)Nd4 tetrahedra, corners with four equivalent Br(3)Rb2Nd3 trigonal bipyramids,  an edgeedge with one Br(4)Rb2Nd3 square pyramid, edges with two equivalent Br(5)Nd4 tetrahedra, and  a faceface with one Br(4)Rb2Nd3 square pyramid. In the fourth Br site, Br(4) is bonded to two equivalent Rb(1), one Nd(2), and two equivalent Nd(1) atoms to form distorted BrRb2Nd3 square pyramids that share corners with four equivalent Br(5)Nd4 tetrahedra, corners with four equivalent Br(3)Rb2Nd3 trigonal bipyramids, edges with two equivalent Br(4)Rb2Nd3 square pyramids,  an edgeedge with one Br(5)Nd4 tetrahedra,  an edgeedge with one Br(3)Rb2Nd3 trigonal bipyramid, and  a faceface with one Br(3)Rb2Nd3 trigonal bipyramid. In the fifth Br site, Br(5) is bonded to two equivalent Nd(1) and two equivalent Nd(2) atoms to form distorted BrNd4 tetrahedra that share corners with four equivalent Br(4)Rb2Nd3 square pyramids, corners with two equivalent Br(5)Nd4 tetrahedra, corners with two equivalent Br(3)Rb2Nd3 trigonal bipyramids,  an edgeedge with one Br(4)Rb2Nd3 square pyramid,  an edgeedge with one Br(5)Nd4 tetrahedra, and edges with two equivalent Br(3)Rb2Nd3 trigonal bipyramids.
RbNd2Br5 crystallizes in the monoclinic P2_1/c space group. Rb(1) is bonded in a 9-coordinate geometry to two equivalent Br(2), two equivalent Br(3), two equivalent Br(4), and three equivalent Br(1) atoms. There is one shorter (3.35 Å) and one longer (3.62 Å) Rb(1)-Br(2) bond length. There is one shorter (3.36 Å) and one longer (3.55 Å) Rb(1)-Br(3) bond length. There is one shorter (3.59 Å) and one longer (3.74 Å) Rb(1)-Br(4) bond length. There are a spread of Rb(1)-Br(1) bond distances ranging from 3.30-3.96 Å. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to two equivalent Br(2), two equivalent Br(3), two equivalent Br(4), and two equivalent Br(5) atoms. There is one shorter (2.97 Å) and one longer (3.64 Å) Nd(1)-Br(2) bond length. There is one shorter (2.98 Å) and one longer (3.44 Å) Nd(1)-Br(3) bond length. There is one shorter (3.03 Å) and one longer (3.15 Å) Nd(1)-Br(4) bond length. There is one shorter (3.07 Å) and one longer (3.17 Å) Nd(1)-Br(5) bond length. In the second Nd site, Nd(2) is bonded in a 7-coordinate geometry to one Br(2), one Br(3), one Br(4), two equivalent Br(1), and two equivalent Br(5) atoms. The Nd(2)-Br(2) bond length is 3.02 Å. The Nd(2)-Br(3) bond length is 3.10 Å. The Nd(2)-Br(4) bond length is 3.19 Å. There is one shorter (3.19 Å) and one longer (3.46 Å) Nd(2)-Br(1) bond length. There is one shorter (3.01 Å) and one longer (3.06 Å) Nd(2)-Br(5) bond length. There are five inequivalent Br sites. In the first Br site, Br(1) is bonded in a 5-coordinate geometry to three equivalent Rb(1) and two equivalent Nd(2) atoms. In the second Br site, Br(2) is bonded in a 5-coordinate geometry to two equivalent Rb(1), one Nd(2), and two equivalent Nd(1) atoms. In the third Br site, Br(3) is bonded to two equivalent Rb(1), one Nd(2), and two equivalent Nd(1) atoms to form distorted BrRb2Nd3 trigonal bipyramids that share corners with four equivalent Br(4)Rb2Nd3 square pyramids, corners with two equivalent Br(5)Nd4 tetrahedra, corners with four equivalent Br(3)Rb2Nd3 trigonal bipyramids,  an edgeedge with one Br(4)Rb2Nd3 square pyramid, edges with two equivalent Br(5)Nd4 tetrahedra, and  a faceface with one Br(4)Rb2Nd3 square pyramid. In the fourth Br site, Br(4) is bonded to two equivalent Rb(1), one Nd(2), and two equivalent Nd(1) atoms to form distorted BrRb2Nd3 square pyramids that share corners with four equivalent Br(5)Nd4 tetrahedra, corners with four equivalent Br(3)Rb2Nd3 trigonal bipyramids, edges with two equivalent Br(4)Rb2Nd3 square pyramids,  an edgeedge with one Br(5)Nd4 tetrahedra,  an edgeedge with one Br(3)Rb2Nd3 trigonal bipyramid, and  a faceface with one Br(3)Rb2Nd3 trigonal bipyramid. In the fifth Br site, Br(5) is bonded to two equivalent Nd(1) and two equivalent Nd(2) atoms to form distorted BrNd4 tetrahedra that share corners with four equivalent Br(4)Rb2Nd3 square pyramids, corners with two equivalent Br(5)Nd4 tetrahedra, corners with two equivalent Br(3)Rb2Nd3 trigonal bipyramids,  an edgeedge with one Br(4)Rb2Nd3 square pyramid,  an edgeedge with one Br(5)Nd4 tetrahedra, and edges with two equivalent Br(3)Rb2Nd3 trigonal bipyramids.