Vacancy-interface-helium interaction in Zr-Nb multi-layer system: A first-principles study

Abstract Driven by our previous experimental findings, we have performed ab-initio simulations to investigate the mechanical properties of and vacancy-interface-helium interaction at Zr-Nb (HCP-BCC) multi-layer composite at Burgers orientation ((0 0 0 2)//(1 1 0) - 〈 2 -1 -1 0 〉 // 〈 1 -1 1 〉 ). HCP-BCC interfaces have not been previously modelled using density functional theory. We present many aspects of this interfacial system such as elastic constants, charge densities and densities of states which, although being crucial in understanding the properties of the materials with interfaces at the atomistic level, are usually ignored by similar works. A thorough analysis of the mechanical properties of Zr-Nb multi-layers has been performed and compared with the behaviour of their constituents in bulk form. The results are promising for applicational purposes as the multi-layers retain most of the mechanical properties of the bulk forms except for the anisotropy index. Furthermore, we present electronic structure analysis which reveals formation of bonding between opposing Zr and Nb atoms and transfer of some net charge at the interface. These results, together with the energetics of the systems, are used to understand the interaction among vacancy, He and the interface which gives insight for foreseeing the behaviour of the system in the presence of He atoms.