Investigation into Structural Variation from 3D to 1D and Strong Second Harmonic Generation of the AHgPS (A = Na, K, Rb, Cs) Family.

The continuous exploration of multinary chalcogenide semiconductors has provided a variety of new functional materials. In this paper, four new quaternary chalcogenides AHgPS (A = Na, K, Rb, Cs) have been prepared by solid-state syntheses. These findings complement the lack of research on this quaternary system. Influenced by the size effect of cations and the coordination mode of Hg, the four compounds crystallize in four different space groups [NaHgPS, 4̅2; KHgPS, 2; RbHgPS, 2/; CsHgPS, 222] and show an interesting evolution from a 3D framework structure to a 1D chain structure. Moreover, all of these compounds feature noncentrosymmetric (NCS) structures except for RbHgPS. The materials exhibit wide band gaps of 2.7 eV < < 3.0 eV. The NCS- related second-harmonic-generation (SHG) property of NaHgPS and KHgPS was also studied. They display strong powder SHG responses (3.14 × AgGaS for NaHgPS; 4.15 × AgGaS for KHgPS), which indicate their intriguing potential as IR nonlinear-optical materials. Moreover, first-principles theoretical calculations were performed to understand the structure-property relationships of these materials.