Na3SiS3F: A Wide Bandgap Fluorothiosilicate with Unique [SiS3F] Unit and High Laser-Induced Damage Threshold

The exploration of antilaser damage wide bandgap infrared (IR) nonlinear optical (NLO) materials is urgent but challenging. Herein, by introducing the idea of fluorination into chalcogenides, a wide bandgap IR NLO material Na 3 SiS 3 F with unprecedented [SiS 3 F] tetrahedra is designed and synthesized. Na 3 SiS 3 F shows a wide bandgap of 4.75 eV (the largest one in the reported quaternary metal chalcogenides), resulting in a high laser damage induced threshold of ≈5 × AgGaS 2 (AGS). Meanwhile, the compound has a moderate NLO response (≈0.3 ×AGS) with phase-matching behavior, large birefringence (0.15@1064 nm), and wide IR transparent region. The introduction of fluorine breaks the structural symmetry and broadens the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap, polarizability anisotropy, and hyperpolarizability of the Si–S tetrahedral unit. The results indicate that Na 3 SiS 3 F is a promising IR NLO material for the high-power laser application and open an avenue for the design of new wide bandgap IR NLO materials based on NLO-active [SiS x F 4− x ] ( x = 1, 2, 3) mixed anionic tetrahedral group.