Institut de Chimie Moléculaire et des Matériaux d'Orsay

Defects and dopants in metal oxides are absolutely crucial to their performance in many applications. Modelling of defect formation and doping is an important part of understanding these processes. The most widely used approach is density functional theory (DFT). However, due to limitations in present approximate exchange-correlation functionals, e.g. the local density and generalised gradient approximations, the DFT description of many defects and dopants in widely used metal oxides is, in the main, entirely incorrect.
We present some results from our work on cerium dioxide and titanium dioxide, where we have used DFT corrected for on-site Coulomb interactions, DFT+U, to study oxygen vacancy formation, metal adsorption and the defects that form upon doping. In general, the DFT+U results are consistent with known experimental data and can also be used to predict the cation oxidation states present upon doping, as well as rationalising experimental findings.

However, DFT+U has its own limitations, principally, that the U parameter is empirical and that U can only be applied to particular species. To this end, we have begun hybrid DFT studies of defects and dopants in metal oxides and present some initial results on this to assess the applicability of DFT+U.