Cs5Sb8 is Magnesium tetraboride-like structured and crystallizes in the monoclinic P2_1/c space group. There are five inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one Sb(1), one Sb(3), two equivalent Sb(2), two equivalent Sb(6), and two equivalent Sb(7) atoms. In the second Cs site, Cs(2) is bonded in a 7-coordinate geometry to one Sb(5), one Sb(7), two equivalent Sb(8), and three equivalent Sb(2) atoms. In the third Cs site, Cs(3) is bonded in a 7-coordinate geometry to one Sb(1), one Sb(3), one Sb(5), one Sb(6), one Sb(8), and two equivalent Sb(4) atoms. In the fourth Cs site, Cs(4) is bonded in a 7-coordinate geometry to one Sb(3), one Sb(5), one Sb(6), two equivalent Sb(1), and two equivalent Sb(4) atoms. In the fifth Cs site, Cs(5) is bonded in a 8-coordinate geometry to one Sb(2), one Sb(4), one Sb(5), one Sb(6), two equivalent Sb(1), and two equivalent Sb(8) atoms. There are eight inequivalent Sb sites. In the first Sb site, Sb(8) is bonded in a 7-coordinate geometry to one Cs(3), two equivalent Cs(2), two equivalent Cs(5), one Sb(1), and one Sb(5) atom. In the second Sb site, Sb(1) is bonded in a 8-coordinate geometry to one Cs(1), one Cs(3), two equivalent Cs(4), two equivalent Cs(5), one Sb(4), and one Sb(8) atom. In the third Sb site, Sb(2) is bonded in a 8-coordinate geometry to one Cs(5), two equivalent Cs(1), three equivalent Cs(2), one Sb(5), and one Sb(7) atom. In the fourth Sb site, Sb(3) is bonded in a 6-coordinate geometry to one Cs(1), one Cs(3), one Cs(4), one Sb(4), one Sb(5), and one Sb(6) atom. In the fifth Sb site, Sb(4) is bonded in a 7-coordinate geometry to one Cs(5), two equivalent Cs(3), two equivalent Cs(4), one Sb(1), and one Sb(3) atom. In the sixth Sb site, Sb(5) is bonded in a 7-coordinate geometry to one Cs(2), one Cs(3), one Cs(4), one Cs(5), one Sb(2), one Sb(3), and one Sb(8) atom. In the seventh Sb site, Sb(6) is bonded in a 7-coordinate geometry to one Cs(3), one Cs(4), one Cs(5), two equivalent Cs(1), one Sb(3), and one Sb(7) atom. In the eighth Sb site, Sb(7) is bonded in a 6-coordinate geometry to one Cs(2), two equivalent Cs(1), one Sb(2), one Sb(6), and one Sb(7) atom.
Cs5Sb8 is Magnesium tetraboride-like structured and crystallizes in the monoclinic P2_1/c space group. There are five inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 8-coordinate geometry to one Sb(1), one Sb(3), two equivalent Sb(2), two equivalent Sb(6), and two equivalent Sb(7) atoms. The Cs(1)-Sb(1) bond length is 4.07 Å. The Cs(1)-Sb(3) bond length is 3.84 Å. There is one shorter (4.24 Å) and one longer (4.28 Å) Cs(1)-Sb(2) bond length. There is one shorter (4.03 Å) and one longer (4.19 Å) Cs(1)-Sb(6) bond length. There is one shorter (3.95 Å) and one longer (4.27 Å) Cs(1)-Sb(7) bond length. In the second Cs site, Cs(2) is bonded in a 7-coordinate geometry to one Sb(5), one Sb(7), two equivalent Sb(8), and three equivalent Sb(2) atoms. The Cs(2)-Sb(5) bond length is 3.98 Å. The Cs(2)-Sb(7) bond length is 3.76 Å. There is one shorter (3.75 Å) and one longer (3.87 Å) Cs(2)-Sb(8) bond length. There are a spread of Cs(2)-Sb(2) bond distances ranging from 4.03-4.27 Å. In the third Cs site, Cs(3) is bonded in a 7-coordinate geometry to one Sb(1), one Sb(3), one Sb(5), one Sb(6), one Sb(8), and two equivalent Sb(4) atoms. The Cs(3)-Sb(1) bond length is 4.41 Å. The Cs(3)-Sb(3) bond length is 3.89 Å. The Cs(3)-Sb(5) bond length is 4.08 Å. The Cs(3)-Sb(6) bond length is 4.17 Å. The Cs(3)-Sb(8) bond length is 3.98 Å. There is one shorter (4.02 Å) and one longer (4.05 Å) Cs(3)-Sb(4) bond length. In the fourth Cs site, Cs(4) is bonded in a 7-coordinate geometry to one Sb(3), one Sb(5), one Sb(6), two equivalent Sb(1), and two equivalent Sb(4) atoms. The Cs(4)-Sb(3) bond length is 4.08 Å. The Cs(4)-Sb(5) bond length is 4.22 Å. The Cs(4)-Sb(6) bond length is 4.14 Å. There is one shorter (3.76 Å) and one longer (3.84 Å) Cs(4)-Sb(1) bond length. There is one shorter (3.94 Å) and one longer (4.02 Å) Cs(4)-Sb(4) bond length. In the fifth Cs site, Cs(5) is bonded in a 8-coordinate geometry to one Sb(2), one Sb(4), one Sb(5), one Sb(6), two equivalent Sb(1), and two equivalent Sb(8) atoms. The Cs(5)-Sb(2) bond length is 4.30 Å. The Cs(5)-Sb(4) bond length is 3.83 Å. The Cs(5)-Sb(5) bond length is 4.10 Å. The Cs(5)-Sb(6) bond length is 3.92 Å. There is one shorter (3.97 Å) and one longer (4.18 Å) Cs(5)-Sb(1) bond length. Both Cs(5)-Sb(8) bond lengths are 4.08 Å. There are eight inequivalent Sb sites. In the first Sb site, Sb(8) is bonded in a 7-coordinate geometry to one Cs(3), two equivalent Cs(2), two equivalent Cs(5), one Sb(1), and one Sb(5) atom. The Sb(8)-Sb(1) bond length is 2.79 Å. The Sb(8)-Sb(5) bond length is 2.91 Å. In the second Sb site, Sb(1) is bonded in a 8-coordinate geometry to one Cs(1), one Cs(3), two equivalent Cs(4), two equivalent Cs(5), one Sb(4), and one Sb(8) atom. The Sb(1)-Sb(4) bond length is 2.86 Å. In the third Sb site, Sb(2) is bonded in a 8-coordinate geometry to one Cs(5), two equivalent Cs(1), three equivalent Cs(2), one Sb(5), and one Sb(7) atom. The Sb(2)-Sb(5) bond length is 2.85 Å. The Sb(2)-Sb(7) bond length is 2.86 Å. In the fourth Sb site, Sb(3) is bonded in a 6-coordinate geometry to one Cs(1), one Cs(3), one Cs(4), one Sb(4), one Sb(5), and one Sb(6) atom. The Sb(3)-Sb(4) bond length is 2.83 Å. The Sb(3)-Sb(5) bond length is 2.97 Å. The Sb(3)-Sb(6) bond length is 2.81 Å. In the fifth Sb site, Sb(4) is bonded in a 7-coordinate geometry to one Cs(5), two equivalent Cs(3), two equivalent Cs(4), one Sb(1), and one Sb(3) atom. In the sixth Sb site, Sb(5) is bonded in a 7-coordinate geometry to one Cs(2), one Cs(3), one Cs(4), one Cs(5), one Sb(2), one Sb(3), and one Sb(8) atom. In the seventh Sb site, Sb(6) is bonded in a 7-coordinate geometry to one Cs(3), one Cs(4), one Cs(5), two equivalent Cs(1), one Sb(3), and one Sb(7) atom. The Sb(6)-Sb(7) bond length is 2.85 Å. In the eighth Sb site, Sb(7) is bonded in a 6-coordinate geometry to one Cs(2), two equivalent Cs(1), one Sb(2), one Sb(6), and one Sb(7) atom. The Sb(7)-Sb(7) bond length is 2.93 Å.