CsSbSe2 crystallizes in the monoclinic P2_1/c space group. Cs(1) is bonded in a 9-coordinate geometry to one Sb(1), four equivalent Se(1), and four equivalent Se(2) atoms. Sb(1) is bonded in a 5-coordinate geometry to one Cs(1), two equivalent Se(1), and two equivalent Se(2) atoms. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to four equivalent Cs(1) and two equivalent Sb(1) atoms. In the second Se site, Se(2) is bonded to four equivalent Cs(1) and two equivalent Sb(1) atoms to form a mixture of distorted edge, corner, and face-sharing SeCs4Sb2 octahedra. The corner-sharing octahedral tilt angles are 43°.
CsSbSe2 crystallizes in the monoclinic P2_1/c space group. Cs(1) is bonded in a 9-coordinate geometry to one Sb(1), four equivalent Se(1), and four equivalent Se(2) atoms. The Cs(1)-Sb(1) bond length is 3.93 Å. There are a spread of Cs(1)-Se(1) bond distances ranging from 3.81-4.11 Å. There are a spread of Cs(1)-Se(2) bond distances ranging from 3.71-3.76 Å. Sb(1) is bonded in a 5-coordinate geometry to one Cs(1), two equivalent Se(1), and two equivalent Se(2) atoms. There is one shorter (2.55 Å) and one longer (3.08 Å) Sb(1)-Se(1) bond length. There is one shorter (2.59 Å) and one longer (2.80 Å) Sb(1)-Se(2) bond length. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to four equivalent Cs(1) and two equivalent Sb(1) atoms. In the second Se site, Se(2) is bonded to four equivalent Cs(1) and two equivalent Sb(1) atoms to form a mixture of distorted edge, corner, and face-sharing SeCs4Sb2 octahedra. The corner-sharing octahedral tilt angles are 43°.