First-principles calculations on mechanical and elastic properties of 2H- and 3R-WS2 under pressure

Abstract The structure, mechanical stability and elastic properties of 2H- and 3R-WS 2 under pressure have been investigated using first-principles calculations based on density functional theory (DFT). The equilibrium lattice parameters of 2H- and 3R-WS 2 at 0 GPa are consistent with experimental and other theoretical values. 2H-WS 2 is more stable than 3R-WS 2 when pressure is less than 5.8 GPa whereas 3R-WS 2 is more stable than 2H-WS 2 when pressure is higher than 5.8 GPa. According to the mechanical stability criteria, both 2H- and 3R-WS 2 exhibit mechanical stability under the pressure range from 0 to 20 GPa. With the increasing pressure, the elastic moduli ( E , B , G ), sound velocities ( v s , v p , v m ) and Debye temperatures of 2H- and 3R-WS 2 increase monotonously whereas volume and specific heat decrease. Large elastic anisotropies in compressibility and in shear were demonstrated for 2H- and 3R-WS 2 at 0 GPa. As the pressure increases, anisotropies in compressibility and in shear become weak for 2H- and 3R-WS 2 . Moreover, 2H- and 3R-WS 2 under pressure have higher hardness and better ductility than those at 0 GPa.