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 x 2 x 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.