NaBa4(GaB4O9)2X3 (X = Cl, Br) with NLO-Active GaO4 Tetrahedral Unit: Experimental and ab Initio Studies

Abstract

Two gallium borates, NaBa4(GaB4O9)2X3 (X = Cl, Br), were synthesized by high temperature solution method. The title compounds crystallize in the same space group P42nm. Their structures feature a 3D [GaB4O9]∞ framework composed of GaO4 tetrahedra and B4O9 groups. NaBa4(GaB4O9)2X3 (X = Cl, Br) compounds show the largest second harmonic generation responses among alkali metal and alkaline-earth metal gallium borates that are 1.5 and 1.1 times that of KH2PO4 (KDP), respectively, and are type I phase-matchable. Combined electronic structure and SHG density calculations as well as local dipole moment analysis have revealed that B–O groups and GaO4 tetrahedron play major roles in SHG response.