Selenite bromide nonlinear optical materials PbGaF(SeO)Br and PbNbO(SeO)Br: synthesis and characterization

Two new isomorphic selenite bromides, namely Pb 2 GaF 2 (SeO 3 ) 2 Br ( 1 ) and Pb 2 NbO 2 (SeO 3 ) 2 Br ( 2 ), were synthesized by mild hydrothermal reactions. These two compounds crystallize in the noncentrosymmertric space group P 2 1 and feature 3D structures consisting of 1D (Pb 2 Br) 3+ cationic chains and 2D [Ga 2 F 4 (SeO 3 ) 4 ] 6− /[Nb 2 O 4 (SeO 3 ) 4 ] 6− anonic chains. As measured, 1 and 2 are phase-matchable and exhibit excellent second harmonic generation (SHG) responses of 4.5 and 1.4 times that of KDP, respectively. Moreover, these two compounds possess wide bandgaps (>3.17 eV) and high thermal stabilities (>425 °C), indicating their suitable performances as potential nonlinear optical materials. First-principle density functional theory (DFT) calculations were also performed to explicate the structure-property relationship. Two new isomorphic NLO materials of Pb 2 GaF 2 (SeO 3 ) 2 Br (4.5 × KDP) and Pb 2 NbO 2 (SeO 3 ) 2 Br (1.4 × KDP) were successfully designed and synthesized.