Experimental and theoretical studies of the ternary thiophosphate PbPS3 featuring ethane-like [P2S6]4- units.

The ternary thiophosphate PbPS3 was synthesized by a high-temperature solid-state reaction using PbS, P and S. Single-crystal X-ray diffraction analysis reveals that the compound crystallizes in the P21/c space group. It features a three-dimensional structure, which consists of [PbS8] hendecahedra and isolated ethane-like [P2S6]4- units. PbPS3 can be easily obtained by different methods and shows high air stability, which is beneficial to its chemical synthesis and large-sized crystal growth. The crystal structure, optical properties and electronic structure of PbPS3 have been researched by experimental methods and first-principles calculations. The results show that PbPS3 has a moderate bandgap (Eg. exp. = 2.60 eV) and birefringence (Δncal. = 0.094@1064 nm), as well as a wide transparent range. Furthermore, to better understand the origin of the birefringence, structure comparisons and theoretical calculations were carried out. With a relatively high physicochemical stability and easy synthesis, PbPS3 can be expected to be a prospective birefringent material.