Effect of uniaxial tensile strain on binding energy of hydrogen atoms to vacancy-carbon-hydrogen complexes in α-iron

Abstract

• The hydrogen binding energy to vacancies under uniaxial tensile strain was calculated. • The binding energy of hydrogen atoms to vacancies decreased with increasing strain. • The binding energy of hydrogen to vacancy-C complexes increased with increasing strain. • The hydrogen retention was estimated under uniaxial tensile strain. The hydrogen binding energy to vacancies or vacancy-carbon complexes in α -Fe under uniaxial tensile strain was calculated using the density functional theory. The solution energies of hydrogen and carbon decreased with an increase in the uniaxial tensile strain. With increasing strain, the binding energy of hydrogen atoms to vacancies also decreases; however, the binding energy of the vacancy-carbon complexes increases. The hydrogen retention was estimated under exposure to hydrogen gas. In the strained area, both the hydrogen concentration of the interstitial hydrogen atoms and the number of hydrogen atoms trapped in the vacancies increased. Therefore, hydrogen retention increased with increasing strain; however, the change in the hydrogen binding energy did not have a strong impact on the hydrogen retention. The presence of vacancies affects hydrogen retention more strongly. Although the binding energy of hydrogen atoms to vacancy-carbon complexes increased, the hydrogen retention in the Fe-C alloy was lower than that in pure Fe.