A first-principles study of the stability of the diamond(111)/WC(001)/Cu(111) interface

The heat sink material operating within the deflector environment is critical for ensuring the stable performance of fusion reactors. Among candidate materials, Cu alloys are regarded as the primary decision for deflector heat sinks due to their high strength and excellent thermal stability. In this study, the interfacial strength of the diamond(111)/WC(001)/Cu(111) system was investigated using a first-principles approach. Both the C- and W-terminal surfaces of WC(001) were considered, and four interfacial models were developed based on computational results. The diamond(111)/WC(001) at the C-terminal and Cu(111)/WC(001) interfaces exhibited stronger charge interactions, higher interfacial adhesion work, and enhanced surface and thermal stability, attributed to the formation of strong interfacial C–C covalent bonds and additional ionic attraction from W atoms, which significantly strengthened interfacial bonding. Although the W-terminal WC surface demonstrated greater inherent surface stability, the introduction of a WC interlayer between diamond(111) and Cu(111) interfaces significantly improved the overall interfacial bonding strength. Furthermore, the bonding strength of the Cu/WC interface was lower than that of the diamond/WC interface, indicating that interfacial failure within the diamond/WC/Cu system would likely initiate at the Cu/WC interface. These results offer atomic-level insights into the structural and bonding characteristics of the diamond/WC/Cu interface, providing a theoretical foundation for the design of advanced heat-sink materials in high-performance fusion reactor applications.