Mechanical properties and their sensitivity to point defects: (HfNbTaTiZr)C high-entropy carbide

High-entropy carbides (HECs) show excellent mechanical properties, but the strengthening mechanism remains unclear. In this work, using first-principles calculations, we comparatively investigated the ideal mechanical properties of $(\mathrm{HfNbTaTiZr})\mathrm{C}$ and its constituent transition metal carbides (TMCs), as well as their sensitivity to point defects. It was found that the properties near the equilibrium point follow the rule of mixture, while those far from the equilibrium state are governed by the weakest link. Most importantly, the introduction of carbon vacancy significantly weakens the mechanical properties of the TMCs, while it less affects and even improves the mechanical properties of the HEC, indicating that the insensitivity to point defects may be one of the significant features of HECs. The results showed that the interaction between lattice distortion and defects would play an important role in improving the mechanical properties of HECs, which may provide guidance for the composition design of HECs.