LiGaF2(IO3)2: A mixed-metal gallium iodate-fluoride with large birefringence and wide band gap

The first mixed alkali-metal gallium iodate-fluoride, namely, LiGaF2(IO3)2, was successfully obtained under hydrothermal conditions. The structure of LiGaF2(IO3)2 features a novel two-dimensional (2D) [GaF2(IO3)2] layer composed of [Ga2F4(IO3)6]4 dimers further bridged by (IO3) groups. LiGaF2(IO3)2 exhibits a wide band gap of 4.33 eV, corresponding to the ultraviolet (UV) absorption edge of 230 nm. Calculations of linear optical property revealed that LiGaF2(IO3)2 has a remarkably large birefringence of 0.181 @1064 nm and 0.206@532 nm, indicating that it is a potential birefringent material that could be used from visible to UV region. This study provides a new method for the future discovery of promising optical crystals.