Quantum-Mechanical Calculations of the Electronic Structure of Ln2Zr2O7 Zirconates (Ln = La, Nd, Sm, Eu, and Gd) with the Pyrochlore Structure

Five compounds with the formula Ln2Zr2O7 (Ln = La, Nd, Sm, Eu, and Gd) were investigated. These materials exhibit important physicochemical properties and find practical applications for the development of high-temperature barriers, gas traps, and the adsorption of actinides in nuclear waste. The investigations were performed using ab initio calculations within the framework of density functional theory employing the full-potential augmented plane-wave method. Quantum-mechanical calculations of the electronic structure and optical spectra of the investigated semiconductors were carried out using the exchange-correlation potential within the generalized gradient approximation (GGA), incorporating GGA + U corrections to account for strong correlations among f- and d-electrons, as well as the GGA + U + mBJ approach to obtain more realistic band gap (Eg) values. Relativistic spin–orbit coupling effects within the electronic systems of heavy-element atoms were also taken into account. The band gaps (Eg) and the complex dielectric function, from which optical properties can be derived, were calculated. A comparison of the calculated total densities of states (DOS) with experimental X-ray photoelectron spectra (XPS) demonstrated the validity of the applied exchange-correlation potential corrections and highlighted the importance of accounting for the spin–orbit splitting of atomic electronic states to accurately reproduce all features of the experimental XPS spectra.