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

A new quaternary chalcogenide Y3GaGe0.5S7 belongs to R3MTQ7 family was discovered for the first time, which was obtained through a conventional solid-state reaction at high temperature. The crystal structure indicates that Y3GaGe0.5S7 crystallizes in hexagonal system P63 space group (a = 9.6204(6) Å, c = 6.0111(7) Å, V = 481.80(8) Å3 and Z = 1). The crystal structure of the title compound is assembled by chains of face-sharing GaS6 octahedra that are surrounded by both discrete Y cations and isolated Ga/GeS4 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/cm2), which is close to 3 times that of AgGaS2 (2.82 MW/cm2). Furthermore, the first-principle calculations are applied to depth analysis the relationship between linear and nonlinear of optical properties and crystal structure.