# 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 Tanguy^{1}, Yu Wang^{1,2}, and Damien Connétable^{2} — ^{1}University Lyon 1, Villeurbanne, France — ^{2}ENSIACET, Toulouse, France

The diffusion coefficient of vacancy-hydrogen clusters (VH_{n}), 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 VH_{n} 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, VH_{n} 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.