Nonlinear Optical Crystal Rb4Sn3Cl2Br8: Synthesis, Structure, and Characterization

A new Sn-based halide compound, Rb4Sn3Cl2Br8, is synthesized by hydrothermal method. This compound crystallizes in orthorhombic noncentrosymmetric space group of Cmc2(1), and the structure is composed of one-dimensional [Sn4Cl2Br8](1)(infinity) chains elongated in parallel to the a-axis. Interestingly, in the [Sn4Cl2Br8](1)(infinity) chains the [SnBr5] and [SnCIBr4] groups hold pyramidal configurations which are found for the first time in Sn-based metal halides. Rb4Sn3Cl2Br8 exhibits a high thermal stability (up to 270 degrees C) and a relatively large bandgap of 2.82 eV. This compound shows a phase-matchable powder second harmonic generation response of 0.5 times of KH2PO4 (KDP), and is the first phase-matchable Sn-based halide nonlinear optical material. The discovery of Rb4Sn3Cl2Br8 will be beneficial to further phase-matchable nonlinear optical materials exploration in Sn-based halides.