Cs3Tl2Br9 crystallizes in the trigonal P-3m1 space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to three equivalent Br(1) and nine equivalent Br(2) atoms to form CsBr12 cuboctahedra that share corners with three equivalent Cs(2)Br12 cuboctahedra, corners with nine equivalent Cs(1)Br12 cuboctahedra, faces with three equivalent Cs(1)Br12 cuboctahedra, faces with three equivalent Cs(2)Br12 cuboctahedra, and faces with five equivalent Tl(1)Br6 octahedra. In the second Cs site, Cs(2) is bonded to six equivalent Br(1) and six equivalent Br(2) atoms to form CsBr12 cuboctahedra that share corners with six equivalent Cs(1)Br12 cuboctahedra, corners with six equivalent Cs(2)Br12 cuboctahedra, faces with six equivalent Cs(1)Br12 cuboctahedra, and faces with six equivalent Tl(1)Br6 octahedra. Tl(1) is bonded to three equivalent Br(1) and three equivalent Br(2) atoms to form TlBr6 octahedra that share corners with three equivalent Tl(1)Br6 octahedra, faces with three equivalent Cs(2)Br12 cuboctahedra, and faces with five equivalent Cs(1)Br12 cuboctahedra. The corner-sharing octahedra are not tilted. There are two inequivalent Br sites. In the first Br site, Br(1) is bonded to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Tl(1) atoms to form a mixture of distorted face and corner-sharing BrCs4Tl2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the second Br site, Br(2) is bonded in a distorted single-bond geometry to one Cs(2), three equivalent Cs(1), and one Tl(1) atom.
Cs3Tl2Br9 crystallizes in the trigonal P-3m1 space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded to three equivalent Br(1) and nine equivalent Br(2) atoms to form CsBr12 cuboctahedra that share corners with three equivalent Cs(2)Br12 cuboctahedra, corners with nine equivalent Cs(1)Br12 cuboctahedra, faces with three equivalent Cs(1)Br12 cuboctahedra, faces with three equivalent Cs(2)Br12 cuboctahedra, and faces with five equivalent Tl(1)Br6 octahedra. All Cs(1)-Br(1) bond lengths are 3.96 Å. There are six shorter (3.93 Å) and three longer (3.96 Å) Cs(1)-Br(2) bond lengths. In the second Cs site, Cs(2) is bonded to six equivalent Br(1) and six equivalent Br(2) atoms to form CsBr12 cuboctahedra that share corners with six equivalent Cs(1)Br12 cuboctahedra, corners with six equivalent Cs(2)Br12 cuboctahedra, faces with six equivalent Cs(1)Br12 cuboctahedra, and faces with six equivalent Tl(1)Br6 octahedra. All Cs(2)-Br(1) bond lengths are 3.93 Å. All Cs(2)-Br(2) bond lengths are 3.87 Å. Tl(1) is bonded to three equivalent Br(1) and three equivalent Br(2) atoms to form TlBr6 octahedra that share corners with three equivalent Tl(1)Br6 octahedra, faces with three equivalent Cs(2)Br12 cuboctahedra, and faces with five equivalent Cs(1)Br12 cuboctahedra. The corner-sharing octahedra are not tilted. All Tl(1)-Br(1) bond lengths are 2.93 Å. All Tl(1)-Br(2) bond lengths are 2.66 Å. There are two inequivalent Br sites. In the first Br site, Br(1) is bonded to two equivalent Cs(1), two equivalent Cs(2), and two equivalent Tl(1) atoms to form a mixture of distorted face and corner-sharing BrCs4Tl2 octahedra. The corner-sharing octahedral tilt angles range from 0-60°. In the second Br site, Br(2) is bonded in a distorted single-bond geometry to one Cs(2), three equivalent Cs(1), and one Tl(1) atom.