Experimental Observations on the Structural Transitions and Metallization in the Two-Dimensional Layered Compound of Cadmium Phosphide Sulfide Under Extreme Conditions

Cadmium phosphorous trisulfide (CdPS3), a prototypical member of metal thio- and selenophosphates (MTPs), has garnered tremendous research interest due to its fundamental properties and potential for novel applications. In this paper, we conducted a comprehensive investigation on the structural evolution and electrical transport behaviors of CdPS3 up to 59.1 GPa under different hydrostatic environments by means of Raman spectroscopy and electrical conductivity measurements. Under non-hydrostatic compression, CdPS3 experienced a succession of structural modifications from C2/m to R3¯ phases at 1.4(5) GPa, then to the isostructural R3¯ phase at 7.8(5) GPa and sequentially to the P3¯1m phase at 29.8(11) GPa, followed by a semiconductor-to-metal transition at 51.3(8) GPa. Under hydrostatic pressurization, ~2.0 GPa pressure hysteresis for the R3¯-to-P3¯1m structural modification and metallization was identified, which can be reasonably interpreted by the impact of deviatoric stress. Upon decompression, the structural transitions of CdPS3 were demonstrated to be reversible with the existence of considerable pressure hysteresis under different hydrostatic environments. Our findings on CdPS3 not only lay a solid foundation for exploring the physicochemical properties of other MTPs under extreme conditions but also push forward its applications in high-performance multifunctional devices.