Crystal structure of NaBa4Ge3S10Cl viewed down [110] direction 

By introducing the highly-electronegative halide anion into chalcogenides, one novel chalcohalide, NaBa₄Ge₃S₁₀Cl, has been synthesized by conventional high temperature solid–state method. It crystallizes in a new structure type of space group P6₃ with a =9.7653(2) Å, c = 12.0581(3) Å and Z = 2. The fundamental unit is the unique [Ge₃S₉] ring comprised of three GeS₄ tetrahedra via sharing corner S atoms. The [Ge₃S₉] rings are arranged to form pseudo layers, which are stacked through Na-Cl-Ba chains to build up the structure. The macroscopic packing of these [Ge₃S₉] rings provides the material moderate NLO response at 2090 nm fundamental light. Furthermore, UV-vis-IR spectroscopy shows that NaBa₄Ge₃S₁₀Cl has a very large band gap of 3.49 eV, which is very beneficial to increase the laser damage threshold and avoid the two-photon absorption problem of the conventional near IR laser pumping sources. 

J. Mater. Chem. C, 2014

The [Ge₃S₉] pseudo-layer (A) and the chain structure (B) in NaBa₄Ge₃S₁₀Cl

The coordination environments of cations in NaBa₄Ge₃S₁₀Cl