First-principles study of hydrogen behavior in α-Pu2O3

The in-depth understanding of hydrogen permeation through plutonium-oxide overlayers is the prerequisite to evaluate the complex hydriding induction period of Pu. In this work, the incorporation, diffusion and dissolution of hydrogen in α-Pu2O3 are investigated by the first-principles calculations and ab initio thermodynamic method based on DFT+U and DFT-D3 schemes. Our study reveals that the hydrogen incorporation is endothermic and the separated H atoms prefer to recombine as H2 molecules rather than reacting with α-Pu2O3. The H and H2 diffusion are both feasible, generally, H will recombine first as H2 and then migrate. Both pressure PH2 and temperature T can promote the hydrogen dissolution in α-Pu2O3. The single H2 molecule incorporation and (H + H2) mixed dissolution will successively appear when increasing PH2. Compared to PuO2, this work indicates that Pu sesquioxide is hardly reduced by hydrogen, but the porous α-Pu2O3 facilitates hydrogen transport in Pu-oxide layers. We present the microscopic picture of hydrogen behavior in the defect-free α-Pu2O3, which could shed some light on the study of the hydriding induction period of Pu.