Pressure‐induced enhancement of mechanical performance in ZrC system

Superhard materials are indispensable for use in cutting and polishing, as well as for nuclear reactor construction. As a candidate for hard material, ZrC has been extensively studied but not in its pressurized phase. Through evolutionary algorithm and density functional theory, we narrowed down the stoichiometry of Zr and C elements at various elevated pressures. The semimetal property of Zr4C4 continues to exist at high pressures but with lower electrical conductivity. Ionic and covalent bonding coexist around the pseudogap for high pressure phases. Both elastic constants and elastic moduli are found to increase steadily with surrounding pressure, connoting the superior mechanical and thermal characteristics of Zr4C4. This can be seen in the increased hardness values, higher melting temperatures, and better machinability indices for Zr4C4 as pressure rises. The predicted G/B and Poison's ratios have both agreed that Zr4C4 exhibits a transition from brittle to ductile behavior when the applied pressure goes above 85 GPa, displaying an overall improved mechanical performance. Analyses of the predicted G/B and Poison's ratios indicate that Zr4C4 undergoes a brittle to ductile transition when the applied pressure exceeds 85 GPa, displaying an overall improved mechanical performance.