Li 8 NaRb 3 (SO 4 ) 6 ·2H 2 O as a new sulfate deep-ultraviolet nonlinear optical material

Sulfates have long been ignored as nonlinear optical materials over the past decades. Here we report a new sulfate deep-ultraviolet nonlinear optical material Li 8 NaRb 3 (SO 4 ) 6 ·2H 2 O synthesized by the facile water solution method. It crystallizes in the asymmetric monoclinic space group C 2 (No. 5). Its single-crystal structure features a three-dimensional framework made up of SO 4 and LiO 4 tetrahedra. Powder second-harmonic generation tests demonstrate that Li 8 NaRb 3 (SO 4 ) 6 ·2H 2 O is phase-matchable with a second-harmonic generation response of about 0.5 × KH 2 PO 4 . Ultraviolet-visible-near-infrared diffuse reflectance spectra illustrate that the ultraviolet cutoff edge of Li 8 NaRb 3 (SO 4 ) 6 ·2H 2 O may be as low as λ < 190 nm. Theoretical calculations reveal that the optical properties of Li 8 NaRb 3 (SO 4 ) 6 ·2H 2 O are mainly attributed to S–O groups. All these results reveal that Li 8 NaRb 3 (SO 4 ) 6 ·2H 2 O 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.