Solvothermal Syntheses of Three-Dimensional Open-Framework Thioantimonates Displaying Nonlinear Optical Responses

The exploration of noncentrosymmetric chalcogenides is important for discovering second-oeder nonlinear optical (NLO) materials. We herein report two new gallium thioantimonates, (NH₄)_2.7Cs_1.3Ga₄SbS₉S_0.3O_0.7H (GaSbS-I) and Cs₄Ga₄SbS₉S_0.3O_0.7H (GaSbS-II), which have been successfully synthesized by facile solvothermal methods. GaSbS-I and GaSbS-II are isostructural, and they exhibit a three-dimensional open framework constructed by [Ga₄S₉Q] units and [SbS₃] units. Both two compounds are second harmonic generation (SHG) active with powder SHG efficiencies of 1.2 and 1.4 times that of the benchmark KH₂PO₄ (KDP) in a non-phase-matching behavior at 1064 nm. The calculated band gaps for GaSbS-I and GaSbS-II are 2.08 and 2.36 eV, respectively, consistent with the experimental values of 2.60 and 2.95 eV. The crystal structures and their optical performance relationship have been clarified by theoretical investigations based on the DFT method.