On the factors enhancing hydrogen trapping in spherical cavities in metals

Using the reaction-diffusion model for hydrogen (H) trapping in spherical cavities in metals (Zibrov and Schmid, 2022), we theoretically analyze the case of H trapping only in chemisorption sites at the cavity surface. We show that the model can be reduced to a form that is similar to the conventional model of H trapping in point defects. The reduced model includes analytical expressions for correction factors to account for correlated H retrapping by the same cavity and inhomogeneous H potential energy landscape in the vicinity of the cavity surface. We show that these correction factors play a significant role in thermal desorption (TDS) simulations only in the case of very low cavity number densities (detrapping-limited regime), which is rarely encountered in experiments.