DFT Investigation of Magnesium-Doped Zirconolite for High-Level Nuclear Waste Immobilization

The black mineral zirconolite (CaZrTi2O7), which is made up of calcium zirconium titanate, has been considered an appropriate waste form for immobilizing radioactive waste. Using Density Functional Theory (DFT), this study examined the impact of magnesium substitution on ceramic nuclear waste from Zirconolite. To explore the material's structural stability and electronic characteristics, a computational simulation was conducted using Quantum ESPRESSO within the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) and Broyden-Fletcher-Golfarb-Shannon (BFGS) relaxation calculations. From the energy range of -2.0 eV to 2.0 eV, the computed electronic band structure was displayed along the symmetry routes. An indirect band gap material with 0.06 eV was revealed by the energy gap between the valence band maximum (VBm) and the conduction band minimum (CBm) at the R2 and Γ sites. The behavior of semiconductors is consistent with this energy gap value. The dopant substitution energy effect was determined to be 1.424 eV, indicating that the Mg-doped Zirconolite's molecular structure remained stable. To sum up, doping CaZrTi2O7 ceramic may promote the production of oxygen, which enhances Magnesium's mobility to the subterranean water molecules inside the geological disposal facility.