First-Principles Study on Mechanical and Optical Behavior of Plutonium Oxide under Typical Structural Phases and...

The chemical corrosion aging of plutonium is a very important topic. It is easy to be corroded and produces oxidation products of various valence states because of its 5f electron orbit between local and non-local. On the one hand, the phase diagram of plutonium and oxygen is complex, so there is still not enough research on typical structural phases. On the other hand, most of the studies on plutonium oxide focus on PuO₂ and Pu₂O₃ with stoichiometric ratio, while the understanding of non-stoichiometric ratio, especially for Pu₂O_3-x, is not deep enough. Based on this, using the DFT + U theoretical scheme of density functional theory, we have systematically studied the structural stability, lattice parameters, electronic structure, mechanical and optical properties of six typical high temperature phases of β-Pu₂O₃, α-Pu₂O_3,γ-Pu₂O_3, PuO, α-PuO_2,γ-PuO₂. Further, the mechanical properties and optical behavior of Pu₂O_3-x under different oxygen vacancy concentrations are analyzed and discussed in detail. The result shows that the elasticity modulus of single crystal in mechanical properties is directly related to the oxygen/plutonium ratio and crystal system. As the number of oxygen vacancies increases, the mechanical constants continue to increase. In terms of optical properties, PuO has the best optical properties, and the light absorption rate decreases with the increase of oxygen vacancy concentration.