Theoretical Calculations Using Density Functional Theory

The theoretical calculations in this part of the work are based on density functional theory,^16,17 using the Vienna ab initio calculation package for first-principles calculations.^18,19 In the calculation process, the projected enhanced wave electric potential (PAW) method is used.²⁰ The exchange-correlation functional uses the generalized gradient approximation (GGA) function combined with the PBE functional^{21 (link)} and the local density approximation (LDA). The PBE + U approximation method is proven to effectively improve the accuracy of the performance calculation of actinide materials.^22,23 Therefore, U = 3.0 is used as a calculation parameter considering the strong correlation effect of 5f orbital, which is consistent with the calculation parameters of Torres and Pegg et al.^24–26 The calculation uses the Monkhorst–Pack method to divide the simple Briyuan area by 5 × 3 × 3 K points.²⁷ The truncation can be 500 eV, and when the atomic energy volume converges to 1.0 × 10⁻⁵ eV per atom, and the atomic force converges below 0.01 eV s⁻¹, the structural relaxation optimization is completed. All calculations are done under periodic boundary conditions. Considering the computational cost, a supercell of size 2 × 2 × 1 is used to calculate properties such as energy and electrons.