Diffusion of interstitial hydrogen plays a key role in potential uses for amorphous metals as membranes for hydrogen purification. It was shown how first-principles-based methods could be used to characterize diffusion of interstitial H in amorphous metals using amorphous Fe3B as an example. Net transport of interstitial H was governed by the transport diffusion coefficient that appears in Fick’s law. This diffusion coefficient was strongly dependent on the interstitial concentration, and was not equal to the self-diffusion coefficient except at dilute interstitial concentrations. Under conditions of practical interest, the concentrations of interstitial H in amorphous metals were not dilute so methods to determine the transport diffusion coefficient must be used if net mass transport was to be described. It was shown how kinetic Monte Carlo simulations of interstitial H diffusion that use rates derived from first-principles calculations could be used to assess both self- and transport diffusion coefficients of H in amorphous metals. These methods will be helpful in efforts to screen amorphous metal alloys as potential membranes for hydrogen purification.

Self-Diffusion and Macroscopic Diffusion of Hydrogen in Amorphous Metals from First-Principles Calculations. S.Hao, D.S.Sholl: Journal of Chemical Physics, 2009, 130[24], 244705