First-principles study of plutonium and cerium solubility in Gd2Sn2O7 pyrochlore

The solubility of Pu and Ce in Gd₂Sn₂O₇ pyrochlore has been investigated by the first principles calculation based on the density functional theory plus Hubbard U correction. The capacity of Pu and Ce substitution in Gd₂Sn₂O₇, as well as the structural properties and the electronic distribution of Gd_2−yPu_ySn₂O₇ (y = 0, 0.5, 1.0, 1.5, 2.0) has been studied. Our energetic analysis suggests that Pu can only perform A-site incorporation in Gd₂Sn₂O₇, and Ce is unable to accomplish substitution in both A and B sites. This result indicates that from the aspect of energy properties, the reliability of Ce surrogate for Pu in the research of stannate pyrochlores requires further investigation. The structural and electronic calculation elucidates that Pu immobilization will weaken the radiation resistance of Gd₂Sn₂O₇ and Pu presents as a reduced charge state in the solid solution.