Mechanical Amorphization-Mediated Self-Healing of Fractured Diamond

Self-healing in covalently bonded matter remains challenging due to the high energy barrier for bond reconstruction. Nanotwinned diamond composites (ntDCs) have demonstrated room-temperature fracture self-healing, while the atomic mechanisms of cracking and self-healing remain unclear. Using atomistic simulations, we uncovered the mechanisms of amorphization-mediated self-healing of fractured ntDCs. Mechanical mismatch at crack-boundary interfaces induced local disorder, forming high-energy amorphous clusters with mixed hybridizations. These amorphous clusters act as sites for self-healing, where the disordered environment promotes a preferential sp2-to-sp3 transition. Furthermore, the simulated pressure-driven self-healing of fractured ntDCs suggested that the posthealing fracture mode is highly dependent on the pressure. Higher pressures facilitate the formation of continuous diamond grains across the fractured interfaces, enhancing the mechanical integrity and recovery efficiency. Our findings provide molecular insights into the self-healing of covalent materials and offer theoretical support for the fabrication of large-sized noncrystalline carbons.