来源：Science Direct
Three new compounds with the composition NaLn9N4Se8 (Ln = Gd – Dy) could be synthesized and structurally characterized. Initially intended to achieve the ternary Ln4N2Se3 representatives, the involvement of sodium-containing reactants led to the formation of these quaternary phases. They crystallize in the monoclinic system with the space group C2/m (lattice parameters: a = 1358 – 1341 pm, b = 399 – 394 pm, c = 1016 – 1026 pm and β = 109.1 – 109.3°) and one formula unit per unit cell. A group-subgroup relationship of both mentioned compound types can be shown, describing the structure of the title compounds as stuffed Sm4N2S3-type arrangement with infinite double-strands
(t = terminal, e = edge-connecting) of cis-edge connected [NLn4]9+ tetrahedra as common structural element. All cations reside in quasi-octahedral coordination spheres (Na/Ln+3+: 6 Se2−, (Ln1)3+: 1 N3− + 5 Se2−, (Ln2)3+: 3 N3− + 3 Se2−). Raman-spectroscopic measurements reveal distinct bands at 374 and 622 cm−1, which can be assigned to vibrations in the mentioned double-strands of fused [NLn4]9+ tetrahedra.