Cs3PSe4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 5-coordinate geometry to one Se(3), two equivalent Se(1), and two equivalent Se(2) atoms. In the second Cs site, Cs(2) is bonded in a 7-coordinate geometry to two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms. P(1) is bonded in a tetrahedral geometry to one Se(1), one Se(3), and two equivalent Se(2) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Cs(1), four equivalent Cs(2), and one P(1) atom to form distorted SeCs6P pentagonal bipyramids that share corners with five equivalent Se(3)Cs5P octahedra, corners with two equivalent Se(1)Cs6P pentagonal bipyramids, edges with two equivalent Se(1)Cs6P pentagonal bipyramids, and faces with two equivalent Se(3)Cs5P octahedra. The corner-sharing octahedral tilt angles range from 12-48°. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one Cs(1), three equivalent Cs(2), and one P(1) atom. In the third Se site, Se(3) is bonded to one Cs(1), four equivalent Cs(2), and one P(1) atom to form SeCs5P octahedra that share corners with five equivalent Se(1)Cs6P pentagonal bipyramids, edges with two equivalent Se(3)Cs5P octahedra, and faces with two equivalent Se(1)Cs6P pentagonal bipyramids.
Cs3PSe4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 5-coordinate geometry to one Se(3), two equivalent Se(1), and two equivalent Se(2) atoms. The Cs(1)-Se(3) bond length is 3.59 Å. There is one shorter (3.68 Å) and one longer (3.69 Å) Cs(1)-Se(1) bond length. Both Cs(1)-Se(2) bond lengths are 3.81 Å. In the second Cs site, Cs(2) is bonded in a 7-coordinate geometry to two equivalent Se(1), two equivalent Se(3), and three equivalent Se(2) atoms. There is one shorter (3.75 Å) and one longer (3.79 Å) Cs(2)-Se(1) bond length. There is one shorter (3.60 Å) and one longer (3.62 Å) Cs(2)-Se(3) bond length. There are a spread of Cs(2)-Se(2) bond distances ranging from 3.68-3.76 Å. P(1) is bonded in a tetrahedral geometry to one Se(1), one Se(3), and two equivalent Se(2) atoms. The P(1)-Se(1) bond length is 2.22 Å. The P(1)-Se(3) bond length is 2.21 Å. Both P(1)-Se(2) bond lengths are 2.21 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Cs(1), four equivalent Cs(2), and one P(1) atom to form distorted SeCs6P pentagonal bipyramids that share corners with five equivalent Se(3)Cs5P octahedra, corners with two equivalent Se(1)Cs6P pentagonal bipyramids, edges with two equivalent Se(1)Cs6P pentagonal bipyramids, and faces with two equivalent Se(3)Cs5P octahedra. The corner-sharing octahedral tilt angles range from 12-48°. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one Cs(1), three equivalent Cs(2), and one P(1) atom. In the third Se site, Se(3) is bonded to one Cs(1), four equivalent Cs(2), and one P(1) atom to form SeCs5P octahedra that share corners with five equivalent Se(1)Cs6P pentagonal bipyramids, edges with two equivalent Se(3)Cs5P octahedra, and faces with two equivalent Se(1)Cs6P pentagonal bipyramids.