Disconnection enhances the second harmonic generation response: synthesis and characterization of Ba23Ga8Sb2S38.

An unusual zero-dimensional quaternary sulfide, Ba(23)Ga(8)Sb(2)S(38), that crystallizes in the noncentrosymmetric polar space group Cmc2(1) was discovered by solid-state reaction of an elemental mixture. The involvement of a second building unit consisting of SbS(3) pyramid and constituting 20% of the structure helped to realize the disconnection of the asymmetric GaS(4) tetrahedra. Such a disconnection leads to the strongest powder second harmonic generation intensity in the IR region among sulfides to date, ~22 times that of commercial AgGaS(2) at an incident laser wavelength of 2.05 μm with the same particle size of 46-74 μm.