Na_3SiS_3F: A Wide Bandgap Fluorothiosilicate with Unique SiS_3F Unit and High Laser-Induced Damage Threshold

摘要

The exploration of antilaser damage wide bandgap infrared (IR) nonlinearoptical (NLO) materials is urgent but challenging. Herein, by introducing theidea of fluorination into chalcogenides, a wide bandgap IR NLO materialNa_3SiS_3F with unprecedented [SiS_3F] tetrahedra is designed and synthesized.Na_3SiS_3F shows a wide bandgap of 4.75 eV (the largest one in the reportedquaternary metal chalcogenides), resulting in a high laser damage inducedthreshold of ≈5 × AgGaS_2 (AGS). Meanwhile, the compound has a moderateNLO response (≈0.3 ×AGS) with phase-matching behavior, largebirefringence (0.15@1064 nm), and wide IR transparent region. Theintroduction of fluorine breaks the structural symmetry and broadens thehighest occupied molecular orbital-lowest unoccupied molecular orbital(HOMO-LUMO) gap, polarizability anisotropy, and hyperpolarizability of theSi–S tetrahedral unit. The results indicate that Na_3SiS_3F is a promising IRNLO material for the high-power laser application and open an avenue for thedesign of new wide bandgap IR NLO materials based on NLO-active[SiS_xF_(4?x)] (x = 1, 2, 3) mixed anionic tetrahedral group.