A Comparative Study on Hydrogen Diffusion in Amorphous and Crystalline Metals Using a Molecular Dynamics Simulation

A comparative study on hydrogen diffusion in amorphous and simple crystalline structures has been carried out using molecular dynamics simulations. The Cu-Zr bulk metallic glass (BMG) system is selected as the model material and a modified embedded-atom method (MEAM) interatomic potential for the Cu-Zr-H ternary system is developed for the atomistic simulation. It is found that the diffusivity of hydrogen in amorphous alloys is lower than that in open structured crystals but higher than that in close-packed crystals. The hydrogen diffusion in amorphous alloys is strongly hydrogen concentration dependent compared to crystals, increasing as the hydrogen content increases, and the Arrhenius plot of hydrogen diffusion in amorphous alloys shows an upward curvature. The reasons to rationalize all the findings are discussed based on the variety of energy state and migration energy barrier for interstitial sites in amorphous alloys.