First-principles simulation of H interacting with transition elements in molybdenum for nuclear material application

Abstract Based on first-principles simulations, we have studied systematically the interaction of transition elements (TEs) with hydrogen (H) in interstitial lattice and vacancy in molybdenum. The results indicated that the stable position of H can be remarkably affected by the TEs, which can be attributed to the valence electron density redistribution surrounding the TEs. The interactions between H and TEs display mainly the attraction, which is explained by the elastic mechanism and the Pauling electronegativity. The elastic mechanism mainly characterizes the H-TE interaction for the TE atoms with the small atomic volume and the large electronegativity in comparison with molybdenum, the opposite cases can be explained by the Pauling electronegativity viewpoint. The appearance of one H atom around the TE atom can affect negatively the binding of the second H. The positive binding energy among H, vacancy and TE can easily lead to the H-TE-vacancy cluster formation in molybdenum. The existence of the TE atom in the vicinity of vacancy can affect the interaction between H and vacancy, while the presence of the H atom around vacancy may influence the interplay between TE and vacancy. The present results give a detailed physical analysis on the interaction between H and TE as well as among H, vacancy and TE in molybdenum and could further help us design the future Mo-based material with regard to the choice of alloy composition for the consideration of the H retention.