Sm3InSe6 crystallizes in the orthorhombic Pnnm space group. There are three inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 8-coordinate geometry to one Se(1), one Se(5), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms. In the second Sm site, Sm(2) is bonded in a 8-coordinate geometry to one Se(1), one Se(2), two equivalent Se(4), two equivalent Se(5), and two equivalent Se(6) atoms. In the third Sm site, Sm(3) is bonded to one Se(1), one Se(4), one Se(6), two equivalent Se(3), and two equivalent Se(5) atoms to form distorted SmSe7 pentagonal bipyramids that share  a cornercorner with one In(1)Se6 octahedra, edges with two equivalent In(2)Se6 octahedra, and edges with two equivalent Sm(3)Se7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. There are two inequivalent In sites. In the first In site, In(1) is bonded to two equivalent Se(6) and four equivalent Se(2) atoms to form InSe6 octahedra that share corners with two equivalent Sm(3)Se7 pentagonal bipyramids and edges with two equivalent In(1)Se6 octahedra. In the second In site, In(2) is bonded to two equivalent Se(3) and four equivalent Se(1) atoms to form InSe6 octahedra that share edges with two equivalent In(2)Se6 octahedra and edges with four equivalent Sm(3)Se7 pentagonal bipyramids. There are six inequivalent Se sites. In the first Se site, Se(5) is bonded to one Sm(1), two equivalent Sm(2), and two equivalent Sm(3) atoms to form distorted SeSm5 trigonal bipyramids that share corners with four equivalent Se(3)Sm4In square pyramids,  a cornercorner with one Se(1)Sm3In2 trigonal bipyramid, corners with two equivalent Se(4)Sm5 trigonal bipyramids, corners with four equivalent Se(6)Sm3In trigonal pyramids,  an edgeedge with one Se(3)Sm4In square pyramid, edges with two equivalent Se(1)Sm3In2 trigonal bipyramids, edges with two equivalent Se(2)Sm3In2 trigonal bipyramids, edges with two equivalent Se(5)Sm5 trigonal bipyramids, edges with three equivalent Se(4)Sm5 trigonal bipyramids, and  an edgeedge with one Se(6)Sm3In trigonal pyramid. In the second Se site, Se(6) is bonded to one Sm(3), two equivalent Sm(2), and one In(1) atom to form distorted SeSm3In trigonal pyramids that share corners with two equivalent Se(3)Sm4In square pyramids, corners with two equivalent Se(2)Sm3In2 trigonal bipyramids, corners with two equivalent Se(4)Sm5 trigonal bipyramids, corners with three equivalent Se(1)Sm3In2 trigonal bipyramids, corners with four equivalent Se(5)Sm5 trigonal bipyramids, corners with three equivalent Se(6)Sm3In trigonal pyramids,  an edgeedge with one Se(5)Sm5 trigonal bipyramid, edges with two equivalent Se(2)Sm3In2 trigonal bipyramids, and  a faceface with one Se(4)Sm5 trigonal bipyramid. In the third Se site, Se(1) is bonded to one Sm(1), one Sm(2), one Sm(3), and two equivalent In(2) atoms to form SeSm3In2 trigonal bipyramids that share  a cornercorner with one Se(4)Sm5 trigonal bipyramid,  a cornercorner with one Se(5)Sm5 trigonal bipyramid, corners with three equivalent Se(2)Sm3In2 trigonal bipyramids, corners with four equivalent Se(1)Sm3In2 trigonal bipyramids, corners with three equivalent Se(6)Sm3In trigonal pyramids, edges with four equivalent Se(3)Sm4In square pyramids,  an edgeedge with one Se(1)Sm3In2 trigonal bipyramid, edges with two equivalent Se(4)Sm5 trigonal bipyramids, and edges with two equivalent Se(5)Sm5 trigonal bipyramids. In the fourth Se site, Se(2) is bonded to one Sm(2), two equivalent Sm(1), and two equivalent In(1) atoms to form SeSm3In2 trigonal bipyramids that share corners with two equivalent Se(3)Sm4In square pyramids, corners with two equivalent Se(2)Sm3In2 trigonal bipyramids, corners with three equivalent Se(1)Sm3In2 trigonal bipyramids, corners with four equivalent Se(4)Sm5 trigonal bipyramids, corners with two equivalent Se(6)Sm3In trigonal pyramids,  an edgeedge with one Se(3)Sm4In square pyramid,  an edgeedge with one Se(4)Sm5 trigonal bipyramid, edges with two equivalent Se(5)Sm5 trigonal bipyramids, edges with three equivalent Se(2)Sm3In2 trigonal bipyramids, and edges with two equivalent Se(6)Sm3In trigonal pyramids. In the fifth Se site, Se(3) is bonded to two equivalent Sm(1), two equivalent Sm(3), and one In(2) atom to form SeSm4In square pyramids that share  a cornercorner with one Se(3)Sm4In square pyramid, corners with two equivalent Se(2)Sm3In2 trigonal bipyramids, corners with four equivalent Se(4)Sm5 trigonal bipyramids, corners with four equivalent Se(5)Sm5 trigonal bipyramids, corners with two equivalent Se(6)Sm3In trigonal pyramids, edges with two equivalent Se(3)Sm4In square pyramids,  an edgeedge with one Se(2)Sm3In2 trigonal bipyramid,  an edgeedge with one Se(4)Sm5 trigonal bipyramid,  an edgeedge with one Se(5)Sm5 trigonal bipyramid, and edges with four equivalent Se(1)Sm3In2 trigonal bipyramids. In the sixth Se site, Se(4) is bonded to one Sm(3), two equivalent Sm(1), and two equivalent Sm(2) atoms to form distorted SeSm5 trigonal bipyramids that share corners with four equivalent Se(3)Sm4In square pyramids,  a cornercorner with one Se(1)Sm3In2 trigonal bipyramid, corners with two equivalent Se(5)Sm5 trigonal bipyramids, corners with four equivalent Se(2)Sm3In2 trigonal bipyramids, corners with two equivalent Se(6)Sm3In trigonal pyramids,  an edgeedge with one Se(3)Sm4In square pyramid,  an edgeedge with one Se(2)Sm3In2 trigonal bipyramid, edges with two equivalent Se(1)Sm3In2 trigonal bipyramids, edges with two equivalent Se(4)Sm5 trigonal bipyramids, edges with three equivalent Se(5)Sm5 trigonal bipyramids, and  a faceface with one Se(6)Sm3In trigonal pyramid.
Sm3InSe6 crystallizes in the orthorhombic Pnnm space group. There are three inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 8-coordinate geometry to one Se(1), one Se(5), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms. The Sm(1)-Se(1) bond length is 3.28 Å. The Sm(1)-Se(5) bond length is 3.22 Å. Both Sm(1)-Se(2) bond lengths are 3.02 Å. Both Sm(1)-Se(3) bond lengths are 3.12 Å. Both Sm(1)-Se(4) bond lengths are 2.96 Å. In the second Sm site, Sm(2) is bonded in a 8-coordinate geometry to one Se(1), one Se(2), two equivalent Se(4), two equivalent Se(5), and two equivalent Se(6) atoms. The Sm(2)-Se(1) bond length is 3.03 Å. The Sm(2)-Se(2) bond length is 3.09 Å. Both Sm(2)-Se(4) bond lengths are 3.07 Å. Both Sm(2)-Se(5) bond lengths are 3.02 Å. Both Sm(2)-Se(6) bond lengths are 2.96 Å. In the third Sm site, Sm(3) is bonded to one Se(1), one Se(4), one Se(6), two equivalent Se(3), and two equivalent Se(5) atoms to form distorted SmSe7 pentagonal bipyramids that share  a cornercorner with one In(1)Se6 octahedra, edges with two equivalent In(2)Se6 octahedra, and edges with two equivalent Sm(3)Se7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. The Sm(3)-Se(1) bond length is 3.08 Å. The Sm(3)-Se(4) bond length is 3.07 Å. The Sm(3)-Se(6) bond length is 2.91 Å. Both Sm(3)-Se(3) bond lengths are 3.00 Å. Both Sm(3)-Se(5) bond lengths are 2.92 Å. There are two inequivalent In sites. In the first In site, In(1) is bonded to two equivalent Se(6) and four equivalent Se(2) atoms to form InSe6 octahedra that share corners with two equivalent Sm(3)Se7 pentagonal bipyramids and edges with two equivalent In(1)Se6 octahedra. Both In(1)-Se(6) bond lengths are 2.58 Å. All In(1)-Se(2) bond lengths are 2.87 Å. In the second In site, In(2) is bonded to two equivalent Se(3) and four equivalent Se(1) atoms to form InSe6 octahedra that share edges with two equivalent In(2)Se6 octahedra and edges with four equivalent Sm(3)Se7 pentagonal bipyramids. Both In(2)-Se(3) bond lengths are 2.75 Å. All In(2)-Se(1) bond lengths are 2.75 Å. There are six inequivalent Se sites. In the first Se site, Se(5) is bonded to one Sm(1), two equivalent Sm(2), and two equivalent Sm(3) atoms to form distorted SeSm5 trigonal bipyramids that share corners with four equivalent Se(3)Sm4In square pyramids,  a cornercorner with one Se(1)Sm3In2 trigonal bipyramid, corners with two equivalent Se(4)Sm5 trigonal bipyramids, corners with four equivalent Se(6)Sm3In trigonal pyramids,  an edgeedge with one Se(3)Sm4In square pyramid, edges with two equivalent Se(1)Sm3In2 trigonal bipyramids, edges with two equivalent Se(2)Sm3In2 trigonal bipyramids, edges with two equivalent Se(5)Sm5 trigonal bipyramids, edges with three equivalent Se(4)Sm5 trigonal bipyramids, and  an edgeedge with one Se(6)Sm3In trigonal pyramid. In the second Se site, Se(6) is bonded to one Sm(3), two equivalent Sm(2), and one In(1) atom to form distorted SeSm3In trigonal pyramids that share corners with two equivalent Se(3)Sm4In square pyramids, corners with two equivalent Se(2)Sm3In2 trigonal bipyramids, corners with two equivalent Se(4)Sm5 trigonal bipyramids, corners with three equivalent Se(1)Sm3In2 trigonal bipyramids, corners with four equivalent Se(5)Sm5 trigonal bipyramids, corners with three equivalent Se(6)Sm3In trigonal pyramids,  an edgeedge with one Se(5)Sm5 trigonal bipyramid, edges with two equivalent Se(2)Sm3In2 trigonal bipyramids, and  a faceface with one Se(4)Sm5 trigonal bipyramid. In the third Se site, Se(1) is bonded to one Sm(1), one Sm(2), one Sm(3), and two equivalent In(2) atoms to form SeSm3In2 trigonal bipyramids that share  a cornercorner with one Se(4)Sm5 trigonal bipyramid,  a cornercorner with one Se(5)Sm5 trigonal bipyramid, corners with three equivalent Se(2)Sm3In2 trigonal bipyramids, corners with four equivalent Se(1)Sm3In2 trigonal bipyramids, corners with three equivalent Se(6)Sm3In trigonal pyramids, edges with four equivalent Se(3)Sm4In square pyramids,  an edgeedge with one Se(1)Sm3In2 trigonal bipyramid, edges with two equivalent Se(4)Sm5 trigonal bipyramids, and edges with two equivalent Se(5)Sm5 trigonal bipyramids. In the fourth Se site, Se(2) is bonded to one Sm(2), two equivalent Sm(1), and two equivalent In(1) atoms to form SeSm3In2 trigonal bipyramids that share corners with two equivalent Se(3)Sm4In square pyramids, corners with two equivalent Se(2)Sm3In2 trigonal bipyramids, corners with three equivalent Se(1)Sm3In2 trigonal bipyramids, corners with four equivalent Se(4)Sm5 trigonal bipyramids, corners with two equivalent Se(6)Sm3In trigonal pyramids,  an edgeedge with one Se(3)Sm4In square pyramid,  an edgeedge with one Se(4)Sm5 trigonal bipyramid, edges with two equivalent Se(5)Sm5 trigonal bipyramids, edges with three equivalent Se(2)Sm3In2 trigonal bipyramids, and edges with two equivalent Se(6)Sm3In trigonal pyramids. In the fifth Se site, Se(3) is bonded to two equivalent Sm(1), two equivalent Sm(3), and one In(2) atom to form SeSm4In square pyramids that share  a cornercorner with one Se(3)Sm4In square pyramid, corners with two equivalent Se(2)Sm3In2 trigonal bipyramids, corners with four equivalent Se(4)Sm5 trigonal bipyramids, corners with four equivalent Se(5)Sm5 trigonal bipyramids, corners with two equivalent Se(6)Sm3In trigonal pyramids, edges with two equivalent Se(3)Sm4In square pyramids,  an edgeedge with one Se(2)Sm3In2 trigonal bipyramid,  an edgeedge with one Se(4)Sm5 trigonal bipyramid,  an edgeedge with one Se(5)Sm5 trigonal bipyramid, and edges with four equivalent Se(1)Sm3In2 trigonal bipyramids. In the sixth Se site, Se(4) is bonded to one Sm(3), two equivalent Sm(1), and two equivalent Sm(2) atoms to form distorted SeSm5 trigonal bipyramids that share corners with four equivalent Se(3)Sm4In square pyramids,  a cornercorner with one Se(1)Sm3In2 trigonal bipyramid, corners with two equivalent Se(5)Sm5 trigonal bipyramids, corners with four equivalent Se(2)Sm3In2 trigonal bipyramids, corners with two equivalent Se(6)Sm3In trigonal pyramids,  an edgeedge with one Se(3)Sm4In square pyramid,  an edgeedge with one Se(2)Sm3In2 trigonal bipyramid, edges with two equivalent Se(1)Sm3In2 trigonal bipyramids, edges with two equivalent Se(4)Sm5 trigonal bipyramids, edges with three equivalent Se(5)Sm5 trigonal bipyramids, and  a faceface with one Se(6)Sm3In trigonal pyramid.