Synthesis, Structure, and optical properties of Y3GaGe0.5S7: A new member in the polar R3MTQ7 family

A new quaternary chalcogenide Y 3 GaGe 0.5 S 7 belongs to R 3 MTQ 7 family was discovered for the first time, which was obtained through a conventional solid-state reaction at high temperature. The crystal structure indicates that Y 3 GaGe 0.5 S 7 crystallizes in hexagonal system P 6 3 space group ( a  = 9.6204(6) Å, c  = 6.0111(7) Å, V  = 481.80(8) Å 3 and Z  = 1). The crystal structure of the title compound is assembled by chains of face-sharing GaS 6 octahedra that are surrounded by both discrete Y cations and isolated Ga/GeS 4 tetrahedra. UV–vis–NIR spectroscopy measurement reveals that the optical band of the title compound is 2.30 eV. It shows weak Second Harmonic Generation (SHG) property but with the high laser-induce damage threshold (LIDT) value (8.55 MW/cm 2 ), which is close to 3 times that of AgGaS 2 (2.82 MW/cm 2 ). Furthermore, the first-principle calculations are applied to depth analysis the relationship between linear and nonlinear of optical properties and crystal structure.