Displacement field induced by a vacancy in nickel and some implications for the solubility of hydrogen

Abstract

The displacement field induced by a vacancy in nickel and its possible implications for the hydrogen solubility in the interstitial sites is investigated up to 1100 K. The displacement field is extracted from our previous atomistic-scale density functional theory calculations and is compared with continuous isotropic models with and without image forces due to the distribution of the defects. This procedure put in forward the contribution of the elastic anisotropy and the vacancy concentration on the elastic displacement field. Then, we calculate the dilatation of the interstitial sites due to the presence of the defect and the local hydrostatic stress acting on them. This local hydrostatic stress modifies the hydrogen solubility in the interstitial sites. Elastic distortions contribute to reduce the local solubility inside the vacancy core and the opposite out of it. Finally, we extract the elastic contribution of the trapping energy of hydrogen in the displacement field of the vacancy. We find that the elastic energy is significant only for the closest interstitial sites of the defect core and limits the attractive electronic contribution to the trapping energy. In addition, we show that the elastic anisotropy and the vacancy concentration have moderate effects on the local solubility in the displacement field close to the defect core.

Keywords:

• nickel
• vacancy
• displacement field
• hydrogen trapping

Acknowledgments

The authors thank the two anonymous reviewers for helpful comments.

Additional information

Funding

Funding. This work was performed using HPC resources from GENCI-IDRIS [grant number 2013-097055], the Centre de Ressources Informatique de Haute-Normandie funded by the Etat/Region program [project 2013004] and the Ymir computational resources of the University of La Rochelle.