Pr2Se3 crystallizes in the tetragonal I-42d space group. There are three inequivalent Pr sites. In the first Pr site, Pr(1) is bonded to two equivalent Se(2), two equivalent Se(3), and four equivalent Se(1) atoms to form a mixture of distorted edge, face, and corner-sharing PrSe8 hexagonal bipyramids. In the second Pr site, Pr(2) is bonded to two equivalent Se(1), two equivalent Se(3), and four equivalent Se(2) atoms to form a mixture of distorted edge, face, and corner-sharing PrSe8 hexagonal bipyramids. In the third Pr site, Pr(3) is bonded in a 8-coordinate geometry to two equivalent Se(2), three equivalent Se(1), and three equivalent Se(3) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Pr(2), two equivalent Pr(1), and three equivalent Pr(3) atoms to form distorted SePr6 octahedra that share corners with three equivalent Se(1)Pr6 octahedra, corners with five equivalent Se(2)Pr5 square pyramids, corners with seven equivalent Se(3)Pr5 square pyramids, edges with two equivalent Se(1)Pr6 octahedra,  an edgeedge with one Se(3)Pr5 square pyramid, edges with three equivalent Se(2)Pr5 square pyramids, faces with two equivalent Se(1)Pr6 octahedra,  a faceface with one Se(2)Pr5 square pyramid, and faces with two equivalent Se(3)Pr5 square pyramids. The corner-sharing octahedral tilt angles range from 18-49°. In the second Se site, Se(2) is bonded to one Pr(1), two equivalent Pr(2), and two equivalent Pr(3) atoms to form SePr5 square pyramids that share corners with five equivalent Se(1)Pr6 octahedra, corners with four equivalent Se(2)Pr5 square pyramids, corners with four equivalent Se(3)Pr5 square pyramids, edges with three equivalent Se(1)Pr6 octahedra,  an edgeedge with one Se(2)Pr5 square pyramid, edges with four equivalent Se(3)Pr5 square pyramids,  a faceface with one Se(1)Pr6 octahedra, and  a faceface with one Se(2)Pr5 square pyramid. The corner-sharing octahedral tilt angles range from 22-49°. In the third Se site, Se(3) is bonded to one Pr(1), one Pr(2), and three equivalent Pr(3) atoms to form distorted SePr5 square pyramids that share corners with seven equivalent Se(1)Pr6 octahedra, corners with four equivalent Se(2)Pr5 square pyramids, corners with five equivalent Se(3)Pr5 square pyramids,  an edgeedge with one Se(1)Pr6 octahedra, edges with four equivalent Se(2)Pr5 square pyramids, faces with two equivalent Se(1)Pr6 octahedra, and  a faceface with one Se(3)Pr5 square pyramid. The corner-sharing octahedral tilt angles range from 13-54°.
Pr2Se3 crystallizes in the tetragonal I-42d space group. There are three inequivalent Pr sites. In the first Pr site, Pr(1) is bonded to two equivalent Se(2), two equivalent Se(3), and four equivalent Se(1) atoms to form a mixture of distorted edge, face, and corner-sharing PrSe8 hexagonal bipyramids. Both Pr(1)-Se(2) bond lengths are 3.00 Å. Both Pr(1)-Se(3) bond lengths are 3.20 Å. There are two shorter (3.03 Å) and two longer (3.18 Å) Pr(1)-Se(1) bond lengths. In the second Pr site, Pr(2) is bonded to two equivalent Se(1), two equivalent Se(3), and four equivalent Se(2) atoms to form a mixture of distorted edge, face, and corner-sharing PrSe8 hexagonal bipyramids. Both Pr(2)-Se(1) bond lengths are 3.27 Å. Both Pr(2)-Se(3) bond lengths are 3.04 Å. There are two shorter (3.01 Å) and two longer (3.19 Å) Pr(2)-Se(2) bond lengths. In the third Pr site, Pr(3) is bonded in a 8-coordinate geometry to two equivalent Se(2), three equivalent Se(1), and three equivalent Se(3) atoms. There is one shorter (2.97 Å) and one longer (3.21 Å) Pr(3)-Se(2) bond length. There are a spread of Pr(3)-Se(1) bond distances ranging from 3.02-3.35 Å. There are a spread of Pr(3)-Se(3) bond distances ranging from 2.98-3.20 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Pr(2), two equivalent Pr(1), and three equivalent Pr(3) atoms to form distorted SePr6 octahedra that share corners with three equivalent Se(1)Pr6 octahedra, corners with five equivalent Se(2)Pr5 square pyramids, corners with seven equivalent Se(3)Pr5 square pyramids, edges with two equivalent Se(1)Pr6 octahedra,  an edgeedge with one Se(3)Pr5 square pyramid, edges with three equivalent Se(2)Pr5 square pyramids, faces with two equivalent Se(1)Pr6 octahedra,  a faceface with one Se(2)Pr5 square pyramid, and faces with two equivalent Se(3)Pr5 square pyramids. The corner-sharing octahedral tilt angles range from 18-49°. In the second Se site, Se(2) is bonded to one Pr(1), two equivalent Pr(2), and two equivalent Pr(3) atoms to form SePr5 square pyramids that share corners with five equivalent Se(1)Pr6 octahedra, corners with four equivalent Se(2)Pr5 square pyramids, corners with four equivalent Se(3)Pr5 square pyramids, edges with three equivalent Se(1)Pr6 octahedra,  an edgeedge with one Se(2)Pr5 square pyramid, edges with four equivalent Se(3)Pr5 square pyramids,  a faceface with one Se(1)Pr6 octahedra, and  a faceface with one Se(2)Pr5 square pyramid. The corner-sharing octahedral tilt angles range from 22-49°. In the third Se site, Se(3) is bonded to one Pr(1), one Pr(2), and three equivalent Pr(3) atoms to form distorted SePr5 square pyramids that share corners with seven equivalent Se(1)Pr6 octahedra, corners with four equivalent Se(2)Pr5 square pyramids, corners with five equivalent Se(3)Pr5 square pyramids,  an edgeedge with one Se(1)Pr6 octahedra, edges with four equivalent Se(2)Pr5 square pyramids, faces with two equivalent Se(1)Pr6 octahedra, and  a faceface with one Se(3)Pr5 square pyramid. The corner-sharing octahedral tilt angles range from 13-54°.