An Effective Strategy for Designing Nonlinear Optical Crystals by Combining the Structure-Directing Property of Oxyfluorides with Chemical Substitution.

Rationally designing a high-performance nonlinear optical (NLO) crystal remains a great ongoing challenge. It involves not only the design of noncentrosymmetric structures but also property optimization. In this communication, a new strategy for effectively designing the NLO crystal has been put forward, that is, using the structure-directing property of oxyfluoride anions to obtain a noncentrosymmetric and polar structure, and then by substitution of IO3 - for isovalent F- anions to further enhance the SHG response. With this strategy, a new iodate fluoride, Ba2 [MoO3 F(IO3 )](MoO3 F2 ) has been successfully designed from the Ba2 (MoO3 F2 )F2 with the cis-directing [MoO4 F2 ]4- groups. It exhibits a large SHG response (≈8×KDP), a wide transparent region (0.30-10.92 μm), a high laser-induced damage threshold (LDT) (88.53 MW cm-2 ), and a large birefringence (≈0.264@532 nm). These indicate Ba2 [MoO3 F(IO3 )](MoO3 F2 ) would be a promising NLO crystal.