Pb5Ga6ZnS15: a noncentrosymmetric framework with chains of T2-supertetrahedra

A novel noncentrosysmmetric sulfide, Pb5Ga6ZnS15 (1), was synthesized for the first time. Its crystal structure revealed the presence of [GaS2](infinity)(-) (chain 1, chains of [GaS4](5-) tetrahedra) and [Ga4S9](infinity)(6-) (chain 2, chains of T2-supertetrahedra) connected by isolated [ZnS4](6-) tetrahedra. Structure correlation with the network constructed solely using chain 1 (Pb(4)Ga(4)GeQ(12)-type) is discussed. Pb5Ga6ZnS15 was calculated to have a suitable static briefringence (Delta n) of 0.1137, and a large nonlinear optical susceptibility d(31) of 58.32 pm V-1 at a wavelength of 2.05 mu m (0.6 eV), much higher than that of the benchmark AgGaS2 (18.14 pm V-1).