LiZn(OH)CO₃ : A Deep-Ultraviolet Nonlinear Optical Hydroxycarbonate Designed from a Diamond-like Structure

Deep-ultraviolet (DUV) nonlinear optical (NLO) crystals are vital to the development of science and state-of-the-art technologies, but the exploration of these important optoelectronic materials is hindered by the contradiction between NLO effect and energy band gap as well as the sensitivity of DUV phase-matching to optical birefringence. Here, in order to achieve a well balanced DUV NLO performance, we chose the diamond-like structure as the prototype template for the material design and synthesized the first DUV NLO hydroxycarbonate crystal, LiZn(OH)CO₃ . This compound simultaneously has a wide band gap (>6.53 eV), a strong second harmonic generation response (ca. 3.2×KDP), and a large birefringence (0.147 at 1064 nm) with the shortest DUV phase-matching capability (λ_PM <190 nm) among all reported NLO carbonates. Moreover, the structure-property relationships in LiZn(OH)CO₃ are analyzed by first-principles calculations. This work presents an effective design strategy to push the NLO performance of hydroxycarbonates into the DUV region.