Berlin 2018 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 20: Topical session (Symposium MM): Hydrogen in Materials
MM 20.8: Vortrag
Dienstag, 13. März 2018, 12:45–13:00, H 0107
Hydrogen influence on diffusion in nickel from first-principles calculations — •Döme Tanguy1, Yu Wang1,2, and Damien Connétable2 — 1University Lyon 1, Villeurbanne, France — 2ENSIACET, Toulouse, France
The diffusion coefficient of vacancy-hydrogen clusters (VHn), at equilibrium, in Ni is evaluated. The key is a good separation of timescales between H diffusion and the metal-vacancy exchange so that cluster diffusion can be treated as an uncorrelated random walk and that H is always in equilibrium before the vacancy-metal exchange. Then, the diffusion coefficient is a sum over jump paths of the equilibrium probability of being in a specific VHn configuration times the corresponding activation terms. The influence of H on the energy barriers for the metal-vacancy exchange are calculated ab initio. It is shown that vacancies are drastically slowed down by H. Nevertheless, at equilibrium, VHn clusters always induce a speed up of metal diffusion, because of the overall enrichment in vacancies. The implications concerning H induced damage, in particular in regards to Ni-Cr oxidation and GB embrittlement, are discussed. Details in Phys. Rev. B 91 094106.