NaNd2Se3 is Caswellsilverite-like structured and crystallizes in the orthorhombic Immm 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 four equivalent Nd(1)Se6 octahedra, edges with two equivalent Na(1)Se6 octahedra, and edges with ten equivalent Nd(1)Se6 octahedra. The corner-sharing octahedra are not tilted. Nd(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form NdSe6 octahedra that share corners with two equivalent Na(1)Se6 octahedra, corners with four equivalent Nd(1)Se6 octahedra, edges with five equivalent Na(1)Se6 octahedra, and edges with seven equivalent Nd(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Na(1) and four equivalent Nd(1) atoms to form a mixture of corner and edge-sharing SeNa2Nd4 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the second Se site, Se(2) is bonded to two equivalent Na(1) and four equivalent Nd(1) atoms to form a mixture of corner and edge-sharing SeNa2Nd4 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.
NaNd2Se3 is Caswellsilverite-like structured and crystallizes in the orthorhombic Immm 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 four equivalent Nd(1)Se6 octahedra, edges with two equivalent Na(1)Se6 octahedra, and edges with ten equivalent Nd(1)Se6 octahedra. The corner-sharing octahedra are not tilted. Both Na(1)-Se(2) bond lengths are 2.98 Å. All Na(1)-Se(1) bond lengths are 2.99 Å. Nd(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form NdSe6 octahedra that share corners with two equivalent Na(1)Se6 octahedra, corners with four equivalent Nd(1)Se6 octahedra, edges with five equivalent Na(1)Se6 octahedra, and edges with seven equivalent Nd(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. Both Nd(1)-Se(2) bond lengths are 2.97 Å. There are two shorter (2.98 Å) and two longer (3.01 Å) Nd(1)-Se(1) bond lengths. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Na(1) and four equivalent Nd(1) atoms to form a mixture of corner and edge-sharing SeNa2Nd4 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the second Se site, Se(2) is bonded to two equivalent Na(1) and four equivalent Nd(1) atoms to form a mixture of corner and edge-sharing SeNa2Nd4 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.