Large second-harmonic generation (SHG) response and broad band gap are two important and competitive parameters. It is difficult to balance them out in one material. In this work, by coupling alkali earth metal (AEM) octahedra with large highest occupied molecular orbital (HOMO)−lowest unoccupied molecular orbital (LUMO) gap and nonlinear optical (NLO)-active tetrahedra units, nine noncentrosymmetric (NCS) compounds, belonging to a new quaternary chalcogenide family A I B 3 II C 3 III Q 8 VI with unique windmill-like [Mg 3 M 3 III Q 24 ] (M III = Al, Ga; Q = S, Se) units constructed by alternated [MgQ 6 ] octahedra and [M III Q 4 ] tetrahedra, are rationally designed and fabricated. The compounds show a stable structural framework but adjustable optical properties. Among them, NaMg 3 Ga 3 Se 8 shows a large SHG response (∼1 × AgGaS 2 (AGS)), wide band gap (in selenide) (2.77 eV), high laser-induced damage threshold (LIDT) (∼2.3 × AGS), and suitable birefringence (0.079@546 nm). It should be a potential candidate for infrared (IR) nonlinear optical (NLO) materials. The results enrich the chemical diversity of chalcogenides and open an avenue for the development of new IR NLO materials through the octahedra and tetrahedra coupled strategy.

Nonlinear optical (NLO) crystals are crucial parts of the tuned laser, which can be used in laser processing, lithography, weapons, and other fields. Until now, the major challenge for this field is how to design NLO crystals with good performance, which is also the commanding point for researchers to face. Structural design is a wonderful strategy for exploring NLO crystals. In this paper, we summarized the structure design strategy “removing center” by analyzing the structure of the classical NLO crystal KBe2BO3F2 and other classical NLO crystals. Through the guidance of the “removing center” strategy, two NLO crystals Rb6Si10O23 and Cs6Si10O23 having large second harmonic generation responses (>1 × KDP) in silicate and deep-ultraviolet cut-off edges, were synthesized and grown. The “removing center” design strategy can induct spontaneous micro symmetry breaking to improve the NLO performance of the crystal. It is expected to become a universal structural design strategy.

A new alkaline-earth metal borate, Sr3B14O24, was successfully synthesized by high temperature solution method. It crystallizes in the monoclinic space group P21/c (No. 14) and features a fundamental building block...

Performance enhancement induced by structural modification has long been the target in materials science fields. Direct evidence to witness the effectivity of one strategy is challenging and necessary. In this work, a tetrahedra‐decoration strategy was proposed to improve the birefringent performance sharply, namely decorating the tetrahedra with a single linear [S2] unit. The strategy was verified by comprehensive characterization of two thiogermanates K2BaGeS4 and K2BaGeS5, which crystallize in the same space group, have similar unit cells and the same units arrangements. Theoretical characterization verified that the [GeS5] group has much larger polarization anisotropy than [GeS4], further demonstrated that the linear [S2] led to the sharp birefringence enlargement of K2BaGeS5 (0.19 vs 0.03 of K2BaGeS4). This work provides a new guiding thought to improve the birefringence performance.