CsGaSe3 crystallizes in the monoclinic P2_1/c space group. Cs(1) is bonded in a 11-coordinate geometry to three equivalent Se(3), four equivalent Se(1), and four equivalent Se(2) atoms. Ga(1) is bonded to one Se(1), one Se(3), and two equivalent Se(2) atoms to form corner-sharing GaSe4 tetrahedra. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted single-bond geometry to four equivalent Cs(1) and one Ga(1) atom. In the second Se site, Se(2) is bonded in a distorted L-shaped geometry to four equivalent Cs(1) and two equivalent Ga(1) atoms. In the third Se site, Se(3) is bonded in a distorted single-bond geometry to three equivalent Cs(1) and one Ga(1) atom.
CsGaSe3 crystallizes in the monoclinic P2_1/c space group. Cs(1) is bonded in a 11-coordinate geometry to three equivalent Se(3), four equivalent Se(1), and four equivalent Se(2) atoms. There are two shorter (3.93 Å) and one longer (4.15 Å) Cs(1)-Se(3) bond length. There are a spread of Cs(1)-Se(1) bond distances ranging from 3.71-4.28 Å. There are a spread of Cs(1)-Se(2) bond distances ranging from 3.77-4.18 Å. Ga(1) is bonded to one Se(1), one Se(3), and two equivalent Se(2) atoms to form corner-sharing GaSe4 tetrahedra. The Ga(1)-Se(1) bond length is 2.42 Å. The Ga(1)-Se(3) bond length is 2.43 Å. There is one shorter (2.39 Å) and one longer (2.41 Å) Ga(1)-Se(2) bond length. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted single-bond geometry to four equivalent Cs(1) and one Ga(1) atom. In the second Se site, Se(2) is bonded in a distorted L-shaped geometry to four equivalent Cs(1) and two equivalent Ga(1) atoms. In the third Se site, Se(3) is bonded in a distorted single-bond geometry to three equivalent Cs(1) and one Ga(1) atom.