A first-principles study of hydrogen surface coverage on δ-Pu (100), (111), and (110) surfaces

Hydriding corrosion of plutonium leads to surface cracking, pitting, and ultimately structural failure. Laboratory experiments demonstrate that hydriding begins on the surface or near the subsurface of plutonium. However, there has not yet been a systematic evaluation of hydrogen surface coverage on plutonium. In this work, we compute the surface energies of the low facet surfaces of face-centered cubic delta-Pu. The adsorption free energies of expected hydrogen structures at low and high coverage are presented along with the likely progression for filling sites as the H-2 partial pressure increases. Implications for near-equilibrium pressure hydride nucleation and non-equilibrium millibar pressure hydriding are discussed.

Automated summary

Hydriding corrosion of plutonium causes surface cracking, pitting, and structural failure. This study calculates the surface energies of low facet surfaces of face-centered cubic delta-Pu, and discusses the adsorption free energies of hydrogen structures at different coverage levels, as well as the progression of filling sites with increasing H-2 partial pressure. Implications for near-equilibrium pressure hydride nucleation and non-equilibrium millibar pressure hydriding are explored.