First-principles calculations and experiments for Ce⁴⁺ effects on structure and chemical stabilities of Zr_1-xCe_xSiO₄

Using Ce atom as the surrogate for tetravalence actinides, the structure stability, chemical bonding and solubility of Zr_1-xCe_xSiO₄ have been investigated by combing first principles calculations and static leach test (MCC-1) experimentally to understand the effect of actinides on stability of ZrSiO₄. The structural analysis indicates that the high symmetry of [CeO₈] polyhedron could well maintain the structural stability of Zr_1-xCe_xSiO₄. However, due to the longer and weaker CeO bond than ZrO bond, LR_Ce is slightly higher than LR_Zr. Besides, the LR_Zr and LR_Ce are highest in acid leaching solution, followed in alkaline leaching solution and deionized water system. Worth noted, the negative solution energy of −22.254 eV indicates the pre-existing Zr vacancy is energetically favorite to accommodate actinides surrogate Ce impurities or quadrivalent actinides with slight structural deformation, showing the strong structural and chemical stabilities of ZrSiO₄.