Abstract: First-principle pseudopotential plane wave calculations and the Nudged Elastic Band method based on the density functional theory (DFT) were used in this article to study the dissociation of molecular hydrogen on a Mg(0001) surface and the subsequent diffusion of atomic hydrogen into the magnesiumsubstrate. First, the dissociation pathway of H2 and the relative barrier were investigated. It was shown that physical adsorption rather than chemisorption of molecular hydrogen was observed in the calculation of the dissociation process of molecular hydrogen. Also, the diffusion process of atomic hydrogen on Mg(0001) was presented. The surface effect, which affected the diffusion of hydrogen obviously, was observed. Finally, comparing the values of the activation energies for the steps of dissociation, diffusion, and desorption, our calculation further showed that the dissociation of H2 and desorption of hydride were the rate-limiting steps.

Key words: First-principle, Potential energy surface, Adsorption energy, Dissociation, Diffusion