Rb2Bi4Se7 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 8-coordinate geometry to one Se(3), two equivalent Se(4), two equivalent Se(7), and three equivalent Se(1) atoms. In the second Rb site, Rb(2) is bonded in a 6-coordinate geometry to one Se(4), one Se(7), two equivalent Se(2), and two equivalent Se(6) atoms. There are four inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one Se(5), one Se(6), two equivalent Se(2), and two equivalent Se(3) atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 9°. In the second Bi site, Bi(2) is bonded to one Se(3), two equivalent Se(6), and three equivalent Se(7) atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 12°. In the third Bi site, Bi(3) is bonded to one Se(3), one Se(4), two equivalent Se(1), and two equivalent Se(5) atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles range from 4-12°. In the fourth Bi site, Bi(4) is bonded to one Se(2), two equivalent Se(4), and three equivalent Se(5) atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles range from 4-9°. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to three equivalent Rb(1) and two equivalent Bi(3) atoms. In the second Se site, Se(2) is bonded to two equivalent Rb(2), one Bi(4), and two equivalent Bi(1) atoms to form SeRb2Bi3 square pyramids that share  a cornercorner with one Se(5)Bi6 octahedra, corners with two equivalent Se(7)Rb3Bi3 pentagonal pyramids, corners with two equivalent Se(3)RbBi4 trigonal bipyramids, corners with four equivalent Se(6)Rb2Bi3 trigonal bipyramids, edges with two equivalent Se(5)Bi6 octahedra, edges with two equivalent Se(4)Rb3Bi3 octahedra, edges with two equivalent Se(2)Rb2Bi3 square pyramids,  an edgeedge with one Se(6)Rb2Bi3 trigonal bipyramid, and  an edgeedge with one Se(3)RbBi4 trigonal bipyramid. The corner-sharing octahedral tilt angles are 10°. In the third Se site, Se(3) is bonded to one Rb(1), one Bi(2), one Bi(3), and two equivalent Bi(1) atoms to form SeRbBi4 trigonal bipyramids that share corners with three equivalent Se(4)Rb3Bi3 octahedra,  a cornercorner with one Se(7)Rb3Bi3 pentagonal pyramid, corners with two equivalent Se(2)Rb2Bi3 square pyramids, corners with two equivalent Se(3)RbBi4 trigonal bipyramids, edges with two equivalent Se(5)Bi6 octahedra, edges with two equivalent Se(7)Rb3Bi3 pentagonal pyramids,  an edgeedge with one Se(2)Rb2Bi3 square pyramid, and edges with two equivalent Se(6)Rb2Bi3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 5-35°. In the fourth Se site, Se(4) is bonded to one Rb(2), two equivalent Rb(1), one Bi(3), and two equivalent Bi(4) atoms to form SeRb3Bi3 octahedra that share corners with two equivalent Se(5)Bi6 octahedra, corners with two equivalent Se(7)Rb3Bi3 pentagonal pyramids, corners with two equivalent Se(6)Rb2Bi3 trigonal bipyramids, corners with three equivalent Se(3)RbBi4 trigonal bipyramids, edges with two equivalent Se(4)Rb3Bi3 octahedra, edges with three equivalent Se(5)Bi6 octahedra, edges with two equivalent Se(2)Rb2Bi3 square pyramids, and  a faceface with one Se(7)Rb3Bi3 pentagonal pyramid. The corner-sharing octahedral tilt angles are 6°. In the fifth Se site, Se(5) is bonded to one Bi(1), two equivalent Bi(3), and three equivalent Bi(4) atoms to form SeBi6 octahedra that share corners with two equivalent Se(4)Rb3Bi3 octahedra,  a cornercorner with one Se(2)Rb2Bi3 square pyramid,  a cornercorner with one Se(6)Rb2Bi3 trigonal bipyramid, edges with three equivalent Se(4)Rb3Bi3 octahedra, edges with four equivalent Se(5)Bi6 octahedra, edges with two equivalent Se(2)Rb2Bi3 square pyramids, and edges with two equivalent Se(3)RbBi4 trigonal bipyramids. The corner-sharing octahedral tilt angles are 6°. In the sixth Se site, Se(6) is bonded to two equivalent Rb(2), one Bi(1), and two equivalent Bi(2) atoms to form distorted SeRb2Bi3 trigonal bipyramids that share  a cornercorner with one Se(5)Bi6 octahedra, corners with two equivalent Se(4)Rb3Bi3 octahedra, corners with two equivalent Se(7)Rb3Bi3 pentagonal pyramids, corners with four equivalent Se(2)Rb2Bi3 square pyramids, edges with three equivalent Se(7)Rb3Bi3 pentagonal pyramids,  an edgeedge with one Se(2)Rb2Bi3 square pyramid, edges with two equivalent Se(6)Rb2Bi3 trigonal bipyramids, and edges with two equivalent Se(3)RbBi4 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 3-45°. In the seventh Se site, Se(7) is bonded to one Rb(2), two equivalent Rb(1), and three equivalent Bi(2) atoms to form distorted SeRb3Bi3 pentagonal pyramids that share corners with two equivalent Se(4)Rb3Bi3 octahedra, corners with two equivalent Se(2)Rb2Bi3 square pyramids,  a cornercorner with one Se(3)RbBi4 trigonal bipyramid, corners with two equivalent Se(6)Rb2Bi3 trigonal bipyramids, edges with four equivalent Se(7)Rb3Bi3 pentagonal pyramids, edges with two equivalent Se(3)RbBi4 trigonal bipyramids, edges with three equivalent Se(6)Rb2Bi3 trigonal bipyramids, and  a faceface with one Se(4)Rb3Bi3 octahedra. The corner-sharing octahedral tilt angles are 56°.
Rb2Bi4Se7 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded in a 8-coordinate geometry to one Se(3), two equivalent Se(4), two equivalent Se(7), and three equivalent Se(1) atoms. The Rb(1)-Se(3) bond length is 3.52 Å. Both Rb(1)-Se(4) bond lengths are 3.73 Å. Both Rb(1)-Se(7) bond lengths are 3.75 Å. There is one shorter (3.43 Å) and two longer (3.66 Å) Rb(1)-Se(1) bond lengths. In the second Rb site, Rb(2) is bonded in a 6-coordinate geometry to one Se(4), one Se(7), two equivalent Se(2), and two equivalent Se(6) atoms. The Rb(2)-Se(4) bond length is 3.54 Å. The Rb(2)-Se(7) bond length is 3.74 Å. Both Rb(2)-Se(2) bond lengths are 3.43 Å. Both Rb(2)-Se(6) bond lengths are 3.44 Å. There are four inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to one Se(5), one Se(6), two equivalent Se(2), and two equivalent Se(3) atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 9°. The Bi(1)-Se(5) bond length is 3.06 Å. The Bi(1)-Se(6) bond length is 2.86 Å. Both Bi(1)-Se(2) bond lengths are 3.00 Å. Both Bi(1)-Se(3) bond lengths are 2.91 Å. In the second Bi site, Bi(2) is bonded to one Se(3), two equivalent Se(6), and three equivalent Se(7) atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 12°. The Bi(2)-Se(3) bond length is 3.03 Å. Both Bi(2)-Se(6) bond lengths are 2.96 Å. There is one shorter (2.86 Å) and two longer (2.99 Å) Bi(2)-Se(7) bond lengths. In the third Bi site, Bi(3) is bonded to one Se(3), one Se(4), two equivalent Se(1), and two equivalent Se(5) atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles range from 4-12°. The Bi(3)-Se(3) bond length is 2.94 Å. The Bi(3)-Se(4) bond length is 2.99 Å. Both Bi(3)-Se(1) bond lengths are 2.79 Å. Both Bi(3)-Se(5) bond lengths are 3.21 Å. In the fourth Bi site, Bi(4) is bonded to one Se(2), two equivalent Se(4), and three equivalent Se(5) atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles range from 4-9°. The Bi(4)-Se(2) bond length is 2.80 Å. Both Bi(4)-Se(4) bond lengths are 2.94 Å. There are two shorter (3.01 Å) and one longer (3.18 Å) Bi(4)-Se(5) bond length. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to three equivalent Rb(1) and two equivalent Bi(3) atoms. In the second Se site, Se(2) is bonded to two equivalent Rb(2), one Bi(4), and two equivalent Bi(1) atoms to form SeRb2Bi3 square pyramids that share  a cornercorner with one Se(5)Bi6 octahedra, corners with two equivalent Se(7)Rb3Bi3 pentagonal pyramids, corners with two equivalent Se(3)RbBi4 trigonal bipyramids, corners with four equivalent Se(6)Rb2Bi3 trigonal bipyramids, edges with two equivalent Se(5)Bi6 octahedra, edges with two equivalent Se(4)Rb3Bi3 octahedra, edges with two equivalent Se(2)Rb2Bi3 square pyramids,  an edgeedge with one Se(6)Rb2Bi3 trigonal bipyramid, and  an edgeedge with one Se(3)RbBi4 trigonal bipyramid. The corner-sharing octahedral tilt angles are 10°. In the third Se site, Se(3) is bonded to one Rb(1), one Bi(2), one Bi(3), and two equivalent Bi(1) atoms to form SeRbBi4 trigonal bipyramids that share corners with three equivalent Se(4)Rb3Bi3 octahedra,  a cornercorner with one Se(7)Rb3Bi3 pentagonal pyramid, corners with two equivalent Se(2)Rb2Bi3 square pyramids, corners with two equivalent Se(3)RbBi4 trigonal bipyramids, edges with two equivalent Se(5)Bi6 octahedra, edges with two equivalent Se(7)Rb3Bi3 pentagonal pyramids,  an edgeedge with one Se(2)Rb2Bi3 square pyramid, and edges with two equivalent Se(6)Rb2Bi3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 5-35°. In the fourth Se site, Se(4) is bonded to one Rb(2), two equivalent Rb(1), one Bi(3), and two equivalent Bi(4) atoms to form SeRb3Bi3 octahedra that share corners with two equivalent Se(5)Bi6 octahedra, corners with two equivalent Se(7)Rb3Bi3 pentagonal pyramids, corners with two equivalent Se(6)Rb2Bi3 trigonal bipyramids, corners with three equivalent Se(3)RbBi4 trigonal bipyramids, edges with two equivalent Se(4)Rb3Bi3 octahedra, edges with three equivalent Se(5)Bi6 octahedra, edges with two equivalent Se(2)Rb2Bi3 square pyramids, and  a faceface with one Se(7)Rb3Bi3 pentagonal pyramid. The corner-sharing octahedral tilt angles are 6°. In the fifth Se site, Se(5) is bonded to one Bi(1), two equivalent Bi(3), and three equivalent Bi(4) atoms to form SeBi6 octahedra that share corners with two equivalent Se(4)Rb3Bi3 octahedra,  a cornercorner with one Se(2)Rb2Bi3 square pyramid,  a cornercorner with one Se(6)Rb2Bi3 trigonal bipyramid, edges with three equivalent Se(4)Rb3Bi3 octahedra, edges with four equivalent Se(5)Bi6 octahedra, edges with two equivalent Se(2)Rb2Bi3 square pyramids, and edges with two equivalent Se(3)RbBi4 trigonal bipyramids. The corner-sharing octahedral tilt angles are 6°. In the sixth Se site, Se(6) is bonded to two equivalent Rb(2), one Bi(1), and two equivalent Bi(2) atoms to form distorted SeRb2Bi3 trigonal bipyramids that share  a cornercorner with one Se(5)Bi6 octahedra, corners with two equivalent Se(4)Rb3Bi3 octahedra, corners with two equivalent Se(7)Rb3Bi3 pentagonal pyramids, corners with four equivalent Se(2)Rb2Bi3 square pyramids, edges with three equivalent Se(7)Rb3Bi3 pentagonal pyramids,  an edgeedge with one Se(2)Rb2Bi3 square pyramid, edges with two equivalent Se(6)Rb2Bi3 trigonal bipyramids, and edges with two equivalent Se(3)RbBi4 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 3-45°. In the seventh Se site, Se(7) is bonded to one Rb(2), two equivalent Rb(1), and three equivalent Bi(2) atoms to form distorted SeRb3Bi3 pentagonal pyramids that share corners with two equivalent Se(4)Rb3Bi3 octahedra, corners with two equivalent Se(2)Rb2Bi3 square pyramids,  a cornercorner with one Se(3)RbBi4 trigonal bipyramid, corners with two equivalent Se(6)Rb2Bi3 trigonal bipyramids, edges with four equivalent Se(7)Rb3Bi3 pentagonal pyramids, edges with two equivalent Se(3)RbBi4 trigonal bipyramids, edges with three equivalent Se(6)Rb2Bi3 trigonal bipyramids, and  a faceface with one Se(4)Rb3Bi3 octahedra. The corner-sharing octahedral tilt angles are 56°.