SrPSe3 crystallizes in the monoclinic P2_1/c space group. Sr(1) is bonded in a 8-coordinate geometry to two equivalent Se(1), three equivalent Se(2), and three equivalent Se(3) atoms. P(1) is bonded to one P(1), one Se(1), one Se(2), and one Se(3) atom to form distorted PPSe3 tetrahedra that share  a cornercorner with one Se(3)Sr3P tetrahedra. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Sr(1) and one P(1) atom. In the second Se site, Se(2) is bonded in a distorted see-saw-like geometry to three equivalent Sr(1) and one P(1) atom. In the third Se site, Se(3) is bonded to three equivalent Sr(1) and one P(1) atom to form distorted SeSr3P tetrahedra that share  a cornercorner with one P(1)PSe3 tetrahedra, corners with four equivalent Se(3)Sr3P tetrahedra, and  an edgeedge with one Se(3)Sr3P tetrahedra.
SrPSe3 crystallizes in the monoclinic P2_1/c space group. Sr(1) is bonded in a 8-coordinate geometry to two equivalent Se(1), three equivalent Se(2), and three equivalent Se(3) atoms. There is one shorter (3.19 Å) and one longer (3.22 Å) Sr(1)-Se(1) bond length. There are a spread of Sr(1)-Se(2) bond distances ranging from 3.28-3.36 Å. There are a spread of Sr(1)-Se(3) bond distances ranging from 3.21-3.37 Å. P(1) is bonded to one P(1), one Se(1), one Se(2), and one Se(3) atom to form distorted PPSe3 tetrahedra that share  a cornercorner with one Se(3)Sr3P tetrahedra. The P(1)-P(1) bond length is 2.25 Å. The P(1)-Se(1) bond length is 2.18 Å. The P(1)-Se(2) bond length is 2.19 Å. The P(1)-Se(3) bond length is 2.19 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Sr(1) and one P(1) atom. In the second Se site, Se(2) is bonded in a distorted see-saw-like geometry to three equivalent Sr(1) and one P(1) atom. In the third Se site, Se(3) is bonded to three equivalent Sr(1) and one P(1) atom to form distorted SeSr3P tetrahedra that share  a cornercorner with one P(1)PSe3 tetrahedra, corners with four equivalent Se(3)Sr3P tetrahedra, and  an edgeedge with one Se(3)Sr3P tetrahedra.