Balanced Second-Order Nonlinear Optical Properties of Adducts CHI₃·(S₈)₃ and AsI₃·(S₈)₃: A Systematic Survey

Two isostructural adducts CHI₃·(S₈)₃ (1) and AsI₃·(S₈)₃ (2) are synthesized by a simple solution method. Both of them crystallize in noncentrosymmetric R3m, featuring van der Waals interaction linked CHI₃ tetrahedra or SbI₃ trigonal pyramids with crown-like S₈ molecules. Both 1 and 2 show strong SHG responses and phase matchability under either 1.064 or 2.1 μm. The results of DFT calculations indicate that the electron transfer happens from S-3p to I-5p orbitals, and both of them demonstrate indirect band gaps. The NLO effects of 1 and 2 are almost fully contributed from the CHI₃ or AsI₃ units. Compared with AgGaS₂, their powder laser damage thresholds are ca. 15 and 51 times higher.