Ab Initio Studies of The Interaction of H with Pu₆Fe

The corrosion of plutonium (Pu) by hydrogen (H) is rapid, however the mechanisms which dictate the hydride formation process is not fully understood. Iron (Fe) is a common impurity in Pu and segregates to the grain boundaries and triple points to form the intermetallic compound Pu₆Fe. To understand the role played by Pu₆Fe in the hydride formation process, density functional theory was employed to compute the energetics and electronic structure of H in interstitial and vacancy sites in Pu₆Fe. H binding was exothermic, with binding energies around -0.4 to -0.2 eV/H atom. With the aid of ab initio molecular dynamics, the interstitial diffusion of H was modeled and the crystal structure for bulk Pu₆Fe hydride was predicted. The role played by the Pu 5f electron states in the hydride formation process will be elucidated.