Influence of Ga on H Reactivity with Ga-Stabilized δ-Pu Alloys

5 years ago

Influence of Ga on H Reactivity with Ga-Stabilized δ-Pu Alloys

Thomas J. Venhaus, Sarah C. Hernandez, Muhammad N. Huda, Scott Richmond

The influence of Ga on the adsorption and solubility of H on Ga-stabilized δ-Pu alloys is investigated using density functional theory and experimentally via a Sieverts’ apparatus. All-electron DFT calculations, with spin–orbit coupling and full relaxations of the surface, are implemented to calculate H adsorption on δ-Pu–Ga alloy (111) surfaces. Chemisorption energies indicate that H prefers a 3-fold hollow site that binds strongly to a Pu-rich environment regardless of Ga concentration of the surface. Sites that include a Ga–H bond yield an increase in chemisorption energies as opposed to chemisorption energies when the H is only bonded to Pu atoms. Also, solution energies for interstitial sites are less exothermic than surface adsorption energies. Experimentally, H-vacancy binding is more exothermic than interstitial binding, and since vacancy binding is the analogue of surface binding, the DFT results are in agreement. Both DFT and experimental results show that with increasing Ga content to 7 at. % Ga there is an increase in H solution energies, thus reducing H solubility. The maximal reduction of H solubility is between 4 and 5 at. % Ga stabilized δ-Pu. The bonding nature of H on the Pu–Ga surface, via analysis of the partial density of states, shows weak hybridizations between the Pu 6d and H 1s states, with a slight decrease of the Pu 5f states near the Fermi level. Overall, Ga will affect the surface adsorption and solubility of H in δ-Pu–Ga alloys.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b04199

DOI: 10.1021/acs.jpcc.7b04199