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SmSe is Wurtzite structured and crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Sm2+ is bonded to four equivalent Se2- atoms to form corner-sharing SmSe4 tetrahedra. All Sm–Se bond lengths are 2.84 Å. Se2- is bonded to four equivalent Sm2+ atoms to form corner-sharing SeSm4 tetrahedra.
Sm3Se4 crystallizes in the cubic I-43d space group. The structure is three-dimensional. Sm+2.67+ is bonded to eight equivalent Se2- atoms to form a mixture of distorted corner, edge, and face-sharing SmSe8 hexagonal bipyramids. There are four shorter (2.97 Å) and four longer (3.16 Å) Sm–Se bond lengths. Se2- is bonded to six equivalent Sm+2.67+ atoms to form a mixture of distorted corner, edge, and face-sharing SeSm6 octahedra. The corner-sharing octahedra tilt angles range from 18–49°.
SmSe is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Sm2+ is bonded to six equivalent Se2- atoms to form a mixture of edge and corner-sharing SmSe6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Sm–Se bond lengths are 2.95 Å. Se2- is bonded to six equivalent Sm2+ atoms to form a mixture of edge and corner-sharing SeSm6 octahedra. The corner-sharing octahedral tilt angles are 0°.
Sm2Se3 is Stibnite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Sm3+ sites. In the first Sm3+ site, Sm3+ is bonded in a 7-coordinate geometry to eight Se2- atoms. There are a spread of Sm–Se bond distances ranging from 3.03–3.50 Å. In the second Sm3+ site, Sm3+ is bonded to seven Se2- atoms to form a mixture of distorted corner and edge-sharing SmSe7 pentagonal bipyramids. There are a spread of Sm–Se bond distances ranging from 2.94–3.02 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to five Sm3+ atoms to form a mixture of distorted corner and edge-sharing SeSm5 square pyramids. In the second Se2- site, Se2- is bonded to five Sm3+ atoms to form a mixture of distorted corner and edge-sharing SeSm5 trigonal bipyramids. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to five Sm3+ atoms.
Sm5Se9 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are five inequivalent Sm+2.40+ sites. In the first Sm+2.40+ site, Sm+2.40+ is bonded in a 9-coordinate geometry to nine Se+1.33- atoms. There are a spread of Sm–Se bond distances ranging from 3.01–3.17 Å. In the second Sm+2.40+ site, Sm+2.40+ is bonded in a 8-coordinate geometry to eight Se+1.33- atoms. There are a spread of Sm–Se bond distances ranging from 2.90–3.18 Å. In the third Sm+2.40+ site, Sm+2.40+ is bonded in a 8-coordinate geometry to eight Se+1.33- atoms. There are a spread of Sm–Se bond distances ranging from 2.93–3.19 Å. In the fourth Sm+2.40+ site, Sm+2.40+ is bonded in a 8-coordinate geometry to eight Se+1.33- atoms. There are a spread of Sm–Se bond distances ranging from 2.95–3.12 Å. In the fifth Sm+2.40+ site, Sm+2.40+ is bonded in a 8-coordinate geometry to eight Se+1.33- atoms. There are a spread of Sm–Se bond distances ranging from 2.95–3.16 Å. There are nine inequivalent Se+1.33- sites. In the first Se+1.33- site, Se+1.33- is bonded in a 5-coordinate geometry to four Sm+2.40+ and one Se+1.33- atom. The Se–Se bond length is 2.52 Å. In the second Se+1.33- site, Se+1.33- is bonded in a 4-coordinate geometry to four Sm+2.40+ atoms. In the third Se+1.33- site, Se+1.33- is bonded to five Sm+2.40+ atoms to form a mixture of distorted corner and edge-sharing SeSm5 trigonal bipyramids. In the fourth Se+1.33- site, Se+1.33- is bonded to five Sm+2.40+ atoms to form a mixture of distorted corner and edge-sharing SeSm5 trigonal bipyramids. In the fifth Se+1.33- site, Se+1.33- is bonded in a 5-coordinate geometry to four Sm+2.40+ and one Se+1.33- atom. The Se–Se bond length is 2.53 Å. In the sixth Se+1.33- site, Se+1.33- is bonded in a 4-coordinate geometry to four Sm+2.40+ atoms. In the seventh Se+1.33- site, Se+1.33- is bonded in a 5-coordinate geometry to five Sm+2.40+ atoms. In the eighth Se+1.33- site, Se+1.33- is bonded to five Sm+2.40+ atoms to form a mixture of distorted corner and edge-sharing SeSm5 trigonal bipyramids. In the ninth Se+1.33- site, Se+1.33- is bonded to five Sm+2.40+ atoms to form a mixture of distorted corner and edge-sharing SeSm5 trigonal bipyramids.
SmSe2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Sm3+ is bonded in a 9-coordinate geometry to nine Se+1.50- atoms. There are a spread of Sm–Se bond distances ranging from 3.02–3.12 Å. There are two inequivalent Se+1.50- sites. In the first Se+1.50- site, Se+1.50- is bonded in a 8-coordinate geometry to four equivalent Sm3+ and four equivalent Se+1.50- atoms. All Se–Se bond lengths are 2.92 Å. In the second Se+1.50- site, Se+1.50- is bonded to five equivalent Sm3+ atoms to form a mixture of distorted corner and edge-sharing SeSm5 trigonal bipyramids.