Dissolution and diffusion behaviors of hydrogen in copper: A first-principles investigation

We have investigated the dissolution and diffusion behaviors of hydrogen (H) in copper (Cu) based on first-principles calculations in combination with the classical thermodynamics models. A single H atom energetically prefers to occupy the octahedral interstitial site (OIS) instead of the tetrahedral interstitial site (TIS). This can be confirmed by the charge density results. The dissolved equilibrium concentration of H is 8.98 × 10−7 at a typical temperature 600 K. We demonstrate that the OIS → TIS → OIS path is the optimal diffusion path of H in Cu with diffusion barrier of 0.23 eV. Double H atoms tend to be paired up at the two neighboring OIS’s along the 〈1 1 0〉 direction with a distance of 2.59 Å and a binding energy of 0.07 eV. This suggests a weak attractive interaction between H atoms, with the implication that self-trapping of H and thus formation of the H2 molecules are quite difficult in the bulk Cu.