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]−∞ (chain 1, chains of [GaS4]5− tetrahedra) and [Ga4S9]6−∞ (chain 2, chains of T2-supertetrahedra) connected by isolated [ZnS4]6− tetrahedra. Structure correlation with the network constructed solely using chain 1 (Pb4Ga4GeQ12-type) is discussed. Pb5Ga6ZnS15 was calculated to have a suitable static briefringence (Δn) of 0.1137, and a large nonlinear optical susceptibility d31 of 58.32 pm V−1 at a wavelength of 2.05 μm (0.6 eV), much higher than that of the benchmark AgGaS2 (18.14 pm V−1).