First Principles Study of the Interfaces Between Tungsten and Transition Metal Carbides: Structures, Energetic and Light Elements Trapping

The fundamental understanding of the structure and energetic properties of interfaces is crucial in materials design and lifetime predictions. In this work, we have performed systematic first-principles calculations to study the stability of the interfaces between tungsten (W) and transition metal carbides (TMC=ZrC, TiC, TaC, HfC, MoC and VC) and predict the trapping of light element impurities (H, He, Li, Be, B, C, N, O, S and P). For all the systems, the coherent W(100)-TMC(100) interfaces have a better stability with lower interface energies than the semi-coherent W(110)-TMC(100) ones. The electronic structure analysis show a strong covalent bonding between the interfacial W and C atoms. The interface and the C vacancy both behave as strong traps to H, He and other light elements, and the interface cohesion is strongly decreased in the presence of impurities. The detrapping energies for H and He at the interface are about 1.14 eV and 2.26 eV, respectively. However, the migration energy barrier of H and He along the interface is less than 0.35 eV, implying that the interface could act as a rapid diffusion path for H and He once they are trapped. The present results provide a consistent explanation for recent experimental phenomena of the interface structure and the H isotope retention in W-ZrC, W-TiC and W-TaC materials under irradiation and further recommend that a multi-scale interface structure may be a good choice for future W-based materials to synergistically enhance the overall performance as plasma facing materials.