NaSm2Se3 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/c space group. Na(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form NaSe6 octahedra that share corners with two equivalent Na(1)Se6 octahedra, corners with two equivalent Sm(1)Se6 octahedra, corners with two equivalent Sm(2)Se6 octahedra, edges with two equivalent Na(1)Se6 octahedra, edges with five equivalent Sm(1)Se6 octahedra, and edges with five equivalent Sm(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form SmSe6 octahedra that share corners with two equivalent Na(1)Se6 octahedra, corners with two equivalent Sm(1)Se6 octahedra, corners with two equivalent Sm(2)Se6 octahedra, edges with two equivalent Sm(1)Se6 octahedra, edges with five equivalent Na(1)Se6 octahedra, and edges with five equivalent Sm(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second Sm site, Sm(2) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form SmSe6 octahedra that share corners with two equivalent Na(1)Se6 octahedra, corners with two equivalent Sm(1)Se6 octahedra, corners with two equivalent Sm(2)Se6 octahedra, edges with two equivalent Sm(2)Se6 octahedra, edges with five equivalent Na(1)Se6 octahedra, and edges with five equivalent Sm(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Na(1), two equivalent Sm(1), and two equivalent Sm(2) atoms to form a mixture of corner and edge-sharing SeNa2Sm4 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second Se site, Se(2) is bonded to two equivalent Na(1), two equivalent Sm(1), and two equivalent Sm(2) atoms to form a mixture of corner and edge-sharing SeNa2Sm4 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.
NaSm2Se3 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/c space group. Na(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form NaSe6 octahedra that share corners with two equivalent Na(1)Se6 octahedra, corners with two equivalent Sm(1)Se6 octahedra, corners with two equivalent Sm(2)Se6 octahedra, edges with two equivalent Na(1)Se6 octahedra, edges with five equivalent Sm(1)Se6 octahedra, and edges with five equivalent Sm(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Both Na(1)-Se(2) bond lengths are 2.95 Å. All Na(1)-Se(1) bond lengths are 2.96 Å. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form SmSe6 octahedra that share corners with two equivalent Na(1)Se6 octahedra, corners with two equivalent Sm(1)Se6 octahedra, corners with two equivalent Sm(2)Se6 octahedra, edges with two equivalent Sm(1)Se6 octahedra, edges with five equivalent Na(1)Se6 octahedra, and edges with five equivalent Sm(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Both Sm(1)-Se(2) bond lengths are 2.96 Å. All Sm(1)-Se(1) bond lengths are 2.94 Å. In the second Sm site, Sm(2) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form SmSe6 octahedra that share corners with two equivalent Na(1)Se6 octahedra, corners with two equivalent Sm(1)Se6 octahedra, corners with two equivalent Sm(2)Se6 octahedra, edges with two equivalent Sm(2)Se6 octahedra, edges with five equivalent Na(1)Se6 octahedra, and edges with five equivalent Sm(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Both Sm(2)-Se(2) bond lengths are 2.94 Å. There are two shorter (2.94 Å) and two longer (2.95 Å) Sm(2)-Se(1) bond lengths. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Na(1), two equivalent Sm(1), and two equivalent Sm(2) atoms to form a mixture of corner and edge-sharing SeNa2Sm4 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second Se site, Se(2) is bonded to two equivalent Na(1), two equivalent Sm(1), and two equivalent Sm(2) atoms to form a mixture of corner and edge-sharing SeNa2Sm4 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.