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Sulfates have long been ignored as nonlinear optical materials over the past decades. Here we report a new sulfate deep-ultraviolet nonlinear optical material Li8NaRb3(SO4)6·2H2O synthesized by the facile water solution method. It crystallizes in the asymmetric monoclinic space group C2 (No. 5). Its single-crystal structure features a three-dimensional framework made up of SO4 and LiO4 tetrahedra. Powder second-harmonic generation tests demonstrate that Li8NaRb3(SO4)6·2H2O is phase-matchable with a second-harmonic generation response of about 0.5 × KH2PO4. Ultraviolet-visible-near-infrared diffuse reflectance spectra illustrate that the ultraviolet cutoff edge of Li8NaRb3(SO4)6·2H2O may be as low as λ ＜ 190 nm. Theoretical calculations reveal that the optical properties of Li8NaRb3(SO4)6·2H2O are mainly attributed to S–O groups. All these results reveal that Li8NaRb3(SO4)6·2H2O may possess potential use in the deep-ultraviolet nonlinear optics field. We believe that the discoveries in our work will attract scientists’ attention to sulfate systems for their potential as deep-ultraviolet nonlinear optical materials. [ABSTRACT FROM AUTHOR]

Few nonlinear optical (NLO) materials are available for deep-UV second-harmonic generation (SHG), limited by the fundamental requirements of the structure-directing optical properties. KBe2BO3F2 is the sole exception, but it suffers from the high toxicity of the compositional beryllium element and a serious layering growth tendency. Here, we report a beryllium-free deep-UV NLO phosphate with honeycomb-like topological structural layers, namely, CsNaMgP2O7. The phosphate exhibits an enhanced SHG response of 1.1 times that of KH2PO4, which is comparable to that of KBe2BO3F2. Based on theoretical analysis, the enhanced SHG response can be well rationalized. Meanwhile, CsNaMgP2O7 possesses a reinforced interlayer bonding of about 2.95 times that of KBe2BO3F2, which is very favorable to mitigate the layering growth tendency. This work will be helpful to better understand the structure–property relationships in deep-UV NLO materials. [ABSTRACT FROM AUTHOR]