Sm3CuSe6 crystallizes in the monoclinic P2_1/m space group. There are four inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 8-coordinate geometry to one Se(2), one Se(6), two equivalent Se(3), two equivalent Se(4), and two equivalent Se(7) atoms. In the second Sm site, Sm(2) is bonded in a 9-coordinate geometry to one Cu(1), one Se(1), one Se(2), one Se(3), one Se(4), two equivalent Se(5), and two equivalent Se(7) atoms. In the third Sm site, Sm(3) is bonded in a 10-coordinate geometry to two equivalent Cu(1), one Se(3), one Se(4), one Se(6), one Se(7), two equivalent Se(1), and two equivalent Se(5) atoms. In the fourth Sm site, Sm(4) is bonded in a 8-coordinate geometry to one Se(2), one Se(6), two equivalent Se(1), two equivalent Se(3), and two equivalent Se(4) atoms. Cu(1) is bonded in a 4-coordinate geometry to one Sm(2), two equivalent Sm(3), one Se(5), one Se(7), and two equivalent Se(1) atoms. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to one Sm(2), one Sm(4), two equivalent Sm(3), and two equivalent Cu(1) atoms. In the second Se site, Se(2) is bonded to one Sm(1), one Sm(4), and two equivalent Sm(2) atoms to form distorted corner-sharing SeSm4 trigonal pyramids. In the third Se site, Se(3) is bonded in a 6-coordinate geometry to one Sm(1), one Sm(2), one Sm(3), one Sm(4), one Se(3), and one Se(5) atom. In the fourth Se site, Se(4) is bonded in a 5-coordinate geometry to one Sm(1), one Sm(2), one Sm(3), one Sm(4), and one Se(4) atom. In the fifth Se site, Se(5) is bonded in a 5-coordinate geometry to two equivalent Sm(2), two equivalent Sm(3), one Cu(1), and one Se(3) atom. In the sixth Se site, Se(6) is bonded to one Sm(1), one Sm(4), and two equivalent Sm(3) atoms to form corner-sharing SeSm4 trigonal pyramids. In the seventh Se site, Se(7) is bonded in a 5-coordinate geometry to one Sm(1), one Sm(3), two equivalent Sm(2), and one Cu(1) atom.
Sm3CuSe6 crystallizes in the monoclinic P2_1/m space group. There are four inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 8-coordinate geometry to one Se(2), one Se(6), two equivalent Se(3), two equivalent Se(4), and two equivalent Se(7) atoms. The Sm(1)-Se(2) bond length is 2.83 Å. The Sm(1)-Se(6) bond length is 2.84 Å. Both Sm(1)-Se(3) bond lengths are 3.06 Å. Both Sm(1)-Se(4) bond lengths are 3.15 Å. Both Sm(1)-Se(7) bond lengths are 3.03 Å. In the second Sm site, Sm(2) is bonded in a 9-coordinate geometry to one Cu(1), one Se(1), one Se(2), one Se(3), one Se(4), two equivalent Se(5), and two equivalent Se(7) atoms. The Sm(2)-Cu(1) bond length is 3.19 Å. The Sm(2)-Se(1) bond length is 2.97 Å. The Sm(2)-Se(2) bond length is 2.98 Å. The Sm(2)-Se(3) bond length is 3.12 Å. The Sm(2)-Se(4) bond length is 3.08 Å. There is one shorter (3.09 Å) and one longer (3.12 Å) Sm(2)-Se(5) bond length. There is one shorter (2.95 Å) and one longer (3.07 Å) Sm(2)-Se(7) bond length. In the third Sm site, Sm(3) is bonded in a 10-coordinate geometry to two equivalent Cu(1), one Se(3), one Se(4), one Se(6), one Se(7), two equivalent Se(1), and two equivalent Se(5) atoms. There is one shorter (3.13 Å) and one longer (3.15 Å) Sm(3)-Cu(1) bond length. The Sm(3)-Se(3) bond length is 3.06 Å. The Sm(3)-Se(4) bond length is 3.07 Å. The Sm(3)-Se(6) bond length is 2.93 Å. The Sm(3)-Se(7) bond length is 2.97 Å. There is one shorter (2.97 Å) and one longer (3.19 Å) Sm(3)-Se(1) bond length. There is one shorter (3.06 Å) and one longer (3.10 Å) Sm(3)-Se(5) bond length. In the fourth Sm site, Sm(4) is bonded in a 8-coordinate geometry to one Se(2), one Se(6), two equivalent Se(1), two equivalent Se(3), and two equivalent Se(4) atoms. The Sm(4)-Se(2) bond length is 2.85 Å. The Sm(4)-Se(6) bond length is 2.84 Å. Both Sm(4)-Se(1) bond lengths are 3.03 Å. Both Sm(4)-Se(3) bond lengths are 3.12 Å. Both Sm(4)-Se(4) bond lengths are 3.07 Å. Cu(1) is bonded in a 4-coordinate geometry to one Sm(2), two equivalent Sm(3), one Se(5), one Se(7), and two equivalent Se(1) atoms. The Cu(1)-Se(5) bond length is 2.40 Å. The Cu(1)-Se(7) bond length is 2.38 Å. There is one shorter (2.48 Å) and one longer (2.59 Å) Cu(1)-Se(1) bond length. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to one Sm(2), one Sm(4), two equivalent Sm(3), and two equivalent Cu(1) atoms. In the second Se site, Se(2) is bonded to one Sm(1), one Sm(4), and two equivalent Sm(2) atoms to form distorted corner-sharing SeSm4 trigonal pyramids. In the third Se site, Se(3) is bonded in a 6-coordinate geometry to one Sm(1), one Sm(2), one Sm(3), one Sm(4), one Se(3), and one Se(5) atom. The Se(3)-Se(3) bond length is 2.50 Å. The Se(3)-Se(5) bond length is 3.02 Å. In the fourth Se site, Se(4) is bonded in a 5-coordinate geometry to one Sm(1), one Sm(2), one Sm(3), one Sm(4), and one Se(4) atom. The Se(4)-Se(4) bond length is 2.47 Å. In the fifth Se site, Se(5) is bonded in a 5-coordinate geometry to two equivalent Sm(2), two equivalent Sm(3), one Cu(1), and one Se(3) atom. In the sixth Se site, Se(6) is bonded to one Sm(1), one Sm(4), and two equivalent Sm(3) atoms to form corner-sharing SeSm4 trigonal pyramids. In the seventh Se site, Se(7) is bonded in a 5-coordinate geometry to one Sm(1), one Sm(3), two equivalent Sm(2), and one Cu(1) atom.