An estimation was made of the interaction energy between hydrogen atoms and an atomic vacancy in alpha iron by using density functional theory. The mobility of an atomic vacancy in a hydrogen environment was than calculated by using the climbing image nudged elastic band method. These analyses showed that two hydrogen atoms were trapped by an atomic vacancy in reasonable hydrogen gaseous environments (300K, 70MPa). A reduction in the vacancy formation energy, from 2.14 to 1.68eV, and an increase in the activation energy for vacancy diffusion, from 0.62 to 1.07eV due to the hydrogen atoms were also observed. The analysis suggested that supersaturated vacancies accumulated locally during plastic deformation in hydrogen environments.

First-Principles Calculation of Hydrogen Effects on the Formation and Diffusion of Vacancies in Alpha Iron: Discussion of the Hydrogen-Enhanced Strain-Induced Vacancy Mechanism. R.Matsumoto, N.Nishiguchi, S.Taketomi, N.Miyazaki: Journal of the Society of Materials Science of Japan, 2014, 63[2], 182-7