Ba 5 Ga 2 SiO 4 S 6 : a Phase-Matching Nonlinear Optical Oxychalcogenide Design via Structural Regulation Originated from Heteroanion Introduction.

Tailored structural regulation to obtain a new non-centrosymmetric (NCS) compound with excellent optical properties is highly desirable but remains a challenge for nonlinear optical (NLO) material design. In this work, centrosymmetric celsian-type BaGa 2 Si 2 O 8 was selected as a template structure, and a novel NCS oxychalcogenide, namely, Ba 5 Ga 2 SiO 4 S 6 , was successfully designed via the introduction of heteroanions under high-temperature solid-state conditions. Ba 5 Ga 2 SiO 4 S 6 adopts the monoclinic space group of Cc (no. 9) and is formed by charges balancing Ba 2+ cations and discrete [Ga 2 SiO 4 S 6 ] clusters made of corner-sharing [SiO 4 ] and [GaOS 3 ] tetrahedra. Notably, Ba 5 Ga 2 SiO 4 S 6 exhibits the critical requirements as a potential UV NLO candidate, including a phase-matching second-harmonic generation intensity (∼1.0 × KDP), a beneficial laser-induced damage threshold (1.2 × KDP), a large birefringence (Δ n = 0.10@546 nm), and a short UV absorption cutoff edge (ca. 0.26 μm). Furthermore, the theoretical calculation is implemented to provide a deeper analysis of the structure-activity relationship. The investigated example of structural regulation originated from heteroanion introduction in this study may offer a feasible strategy for high-performance NLO candidate design.