keywords: DFT, CaZrTi2¬¬O7, zirconolite, immobilisation, electronic properties
Zirconolite (CaZrTi2O7) has been acknowledged as the favourable candidate for high level radioactive waste immobilisation due to its effectiveness in aqueous durability, chemical flexibility, waste loading and radiation tolerance. In this study, the structural and electronic properties of zirconolitehave investigated using Density Functional Theory (DFT) within generalized gradient approximation (GGA) as implemented in Quantum ESPRESSO (QE). It was found that the zirconolite structure is stable. The calculated electronic band structure of zirconolite shown along a high symmetry direction and the energy range of band structure is plotted from 0.00 eV to 3.0 eV, the energy separation between the conduction band maximum and valence band minimum occurred at the R2 and T2 points, indicating that zirconolite is an indirect band gap material with an approximate value of 2.90 eV energy gap, this value is consistent with previous DFT result but less than the experimental result whichreveals the material’s semi-conductivity. The calculated density of the state (DOS) shows the domination of different states in both the valence band and the conduction band while projected density of the state (PDOS) indicates s-orbital of Zr, s-orbital of Ca and p-orbital of Ti atoms are responsible for material properties in the valence band near the Fermi level. The type of chemical bond and charge transfer between the anions and the cations was examined by charge density distribution.