First-Principles Calculations of the Mechanical and Elastic Properties of 2Hc- and 2Ha-WS2/CrS2 Under Pressure

Abstract By utilizing the first-principles method, the pressure-induced effects on phase transition, mechanical stability, and elastic properties of WS 2 /CrS 2 are investigated in the pressure range from 0 to 80 GPa. Transitions from 2H c to 2H a for WS 2 and CrS 2 are found to occur at 17.5 and 25 GPa, respectively. It is found that both 2H a and 2H c phases of WS 2 and CrS 2 meet the mechanical stability criteria up to 80 GPa, suggesting that those structures are mechanically stable. The bulk and shear modulus anisotropy of the two phases of WS 2 and CrS 2 decrease rapidly under pressure and, finally, trend to isotropy. With increasing pressure, the elastic moduli ( Y , B , and G ), sound velocities ( v s , v p , v m ), and Debye temperatures (Θ) of 2H a and 2H c of WS 2 and CrS 2 increase monotonously. Moreover, the Debye temperature (Θ) of 2H c phase is higher than that of 2H a phase for both WS 2 and CrS 2 . The bulk, shear, and Young’s modulus, Poisson coefficient, and brittle/ductile behaviour are estimated. The percentages of anisotropy in compressibility and shear and the ratio of bulk to shear modulus ( B / G ) are also studied.