Pb2TiFO(SeO3)2Br: A New Polar Compound with the Strongest Second Harmonic Generation in the Selenite Bromide Family

Combining different acentric functional units is an effective strategy to design and synthesize new nonlinear optical (NLO) crystals. Guided by this idea, two new polar selenite bromide compounds, Pb2TiFO(SeO3)2Br and Pb2VO2(SeO3)2Br, have been synthesized via hydrothermal method. Attributable to the synergistic effect of multiple NLO-active units, Pb2TiFO(SeO3)2Br exhibits the largest second harmonic generation (SHG) response among all reported NLO selenite bromides under 1064 nm laser radiation, about 10.0 × KH2PO4 (KDP). Pb2TiFO(SeO3)2Br has no obvious absorption from the near-ultraviolet (UV) to the middle-infrared (IR) region. Meanwhile, the structure–property relationship in Pb2TiFO(SeO3)2Br was also elucidated by first-principles studies.