Strained behavior of monolayer HfS2, HfSe2, and HfTe2 from molecular dynamic simulations

We have employed the classical molecular dynamics (MD) simulations to investigate the mechanical properties of the HfX2 (X=S, Se, Te) monolayers (MLs) -the emerging nano-materials possessing highly attractive for functional electronic and optoelectronic systems. The studied materials have exhibited isotropic mechanical properties in armchair and zigzag directions. Both the stress-strain curves and the structural evolution around the fracture point have indicated that materials have undergone a brittle fracture once up to the ultimate stress. At the same temperature, HfS2 ML exhibits a higher Young's modulus than HfSe2, yet HfSe2 possesses slightly larger fracture strain, fracture stress, and toughness compared to HfS2. Among the three materials, HfTe2 displays the poorest mechanical performance. The calculated results may be attributed to materials' distinct microstructures and bond lengths. It's found that temperature can obviously affect the mechanical properties of materials. For example, as the temperature increases, the calculations show that the fracture strain, fracture stress and toughness have obviously decreased. However, the Young's modulus decreases slightly and linearly with the increasing temperature. These results suggest temperature can induce the mechanical degradation.