Interplay between Gd and oxygen vacancy on the electronic properties and defect chemistry of Gd-doped CeO₂: A DFT + U study

The electronic properties and defect chemistry of Gd-doped CeO₂ have been systematically investigated using the density functional theory with the Hubbard U correction. Three types of doping are considered in 2 × 2 × 2 CeO₂ supercell: one Gd substitution for Ce, one Gd substitution and one oxygen vacancy, and 2 Gd substitutions and an oxygen vacancy. Detailed thermodynamic and kinetic investigations have been conducted to elaborate the favorability for the formation of these dopants in CeO₂. Results show that Gd substitutions and oxygen vacancy tend to cluster in the form of Gd-V_O-Gd via strong interaction between donor (V_O) and acceptor (substitutional Gd) states. Such a donor–acceptor interaction is found to lead to charge compensation. In contrast, a single or isolated Gd substitution hardly influences the defect chemistry of oxygen vacancy. This work is expected to offer valuable insights into the Gd-doped CeO₂, beneficial for widening the practical applications of CeO₂-based materials and devices.