Strongest Second Harmonic Generation in the Polar R3MTQ7 Family: Atomic Distribution Induced Nonlinear Optical Cooperation.

Yellow single crystals of the Ln3MTQ7 NLO material family, La3Ga0.5 (Ge0.5/Ga0.5)S7 (I), La3In0.5 (Ge0.5/In0.5)S7 (II), Sm3Ga0.5 (Ge0.5/Ga0.5)S7 (III), La3In0.33GeS7 (IV), Sm3In0.33GeS7(V), and Gd3In0.33GeS7 (VI) are prepared by solid state reaction of stoichiometric amounts of rare earths, Ge, In (Ga), and S (950-980 °C, 100-120 h; controlled cooling).