Pu-Doping-Induced Weberite-like Local Motifs and Enhanced Immobilization in Gd2Zr2O7 Pyrochlore: A DFT + U Study

Abstract

Abstract This study employs density functional theory with the Hubbard U correction (DFT + U) method to investigate how Pu incorporation into distinct sites (Gd or Zr) in Gd2Zr2O7 governs locally weberite-like disorder and subsequently influences Pu immobilization behavior. We reveal that incorporating Pu into Zr sites induces spontaneous 48f oxygen displacement toward vacant 8a sites, forming weberite-like local motifs characterized by 7-fold coordinated Pu. This structural disorder increases the oxygen positional parameter xO48f and elongates average Pu–O48f bonds. Solution energies confirm preferential Pu immobilization at Zr sites, where the locally disordered weberite-like arrangement provides additional stabilization. Electronic structure analysis reveals that Pu incorporation into Zr sites induces stronger Pu–O hybridization than Gd-site substitution. Crucially, the 7-coordinated Pu in locally disordered weberite-like arrangements exhibits pronounced ionic character, which could favor Pu immobilization at Zr sites in Gd2Zr2O7. These results suggest that local weberite-like disorder may be a key mechanism for optimizing Pu immobilization in pyrochlore ceramics.