Synthesis, Crystal, and Electronic Structures, and Second Harmonic Generation of La₄Ge₃S₁₂

The crystal structure of La 4 Ge 3 S 12 has been known to be noncentrosymmetric for almost four decades. This characteristic inversion symmetry breaking suggests the presence of nonlinear optical properties. Yet, only recently have nonlinear optical phenomena such as second harmonic generation (SHG) been reported in this material. In this study, La 4 Ge 3 S 12 is synthesized using the direct reaction method and the composition, crystal structure, and electronic structure are characterized using electron probe microanalysis, powder and single‐crystal X‐ray diffraction, and X‐ray photoelectron spectroscopy. The experimentally measured electronic structure is in line with that obtained using first‐principles calculations. In addition, we observed the nonlinear optical properties of La 4 Ge 3 S 12 in response to an ultrashort infrared pulsed laser. It is found that the intensity of the SHG depends quadratically on the intensity of the incident light, mirroring the intrinsic nature of nonlinear optics.