Self-diffusion and macroscopic diffusion of hydrogen in amorphous metalsfrom first-principles calculations

摘要

Diffusion of interstitial hydrogen plays a key role in potential uses for amorphous metals asmembranes for hydrogen purification. We show how first principles-based methods can be used tocharacterize diffusion of interstitial H in amorphous metals using amorphous Fe3B as an example.Net transport of interstitial H is governed by the transport diffusion coefficient that appears in Fick'slaw. This diffusion coefficient is strongly dependent on the interstitial concentration, and is not equalto the self-diffusion coefficient except at dilute interstitial concentrations. Under conditions ofpractical interest, the concentrations of interstitial H in amorphous metals are nondilute so methodsto determine the transport diffusion coefficient must be used if net mass transport is to be described.We show how kinetic Monte Carlo simulations of interstitial H diffusion that use rates derived fromfirst-principles calculations can be used to assess both self- and transport diffusion coefficients of Hin amorphous metals. These methods will be helpful in efforts to screen amorphous metal alloys aspotential membranes for hydrogen purification.