First-Principles Study of Hydrogen Behaviors in $\alpha$-Pu$_{2}$O$_{3}$

TL;DR

This study uses first-principles calculations to explore how hydrogen interacts with α-Pu₂O₃, revealing insights into hydrogen incorporation, diffusion, and its implications for hydriding in plutonium oxides.

Contribution

It provides a microscopic understanding of hydrogen behaviors in α-Pu₂O₃ using first-principles methods, which was previously unexplored.

Findings

Hydrogen incorporation is endothermic and H atoms prefer to form H₂ molecules.

Hydrogen diffusion and dissolution are feasible and promoted by pressure and temperature.

Pu sesquioxide is resistant to reduction by hydrogen, but α-Pu₂O₃ facilitates hydrogen transport.

Abstract

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 $\alpha$-Pu$_{2}$O$_{3}$ are investigated by the first-principles calculations and $\textit{ab initio}$ 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 H$_{2}$ molecules rather than reacting with $\alpha$-Pu$_{2}$O$_{3}$. The H and H$_{2}$ diffusion are both feasible, generally, H will recombine first as H$_{2}$ and then migrate. Both pressure P$_{H2}$ and temperature can promote the hydrogen dissolution in $\alpha$-Pu$_{2}$O$_{3}$. The single H$_{2}$ molecule incorporation and (H+H$_{2}$) mixed dissolution will successively appear when increasing P$_{H2}$. Compared to PuO$_{2}$, this work indicates that Pu sesquioxide is hardly reduced by hydrogen, but the porous $\alpha$-Pu$_{2}$O$_{3}$ facilitates hydrogen transport in Pu oxide layers. We presents the microscopic picture of hydrogen behaviors in the defect-free $\alpha$-Pu$_{2}$O$_{3}$, which could shed some light on the study of the hydriding induction period of Pu.