Choice of U for DFT plus U Calculations for Titanium Oxides

Many recent articles have suggested that density functional theory (DFT) with the generalized-gradient approximation does not provide the correct electronic structure for the oxides of titanium. The current opinion is that a Hubbard U correction improves the DFT results. There is no generally accepted method for deciding what the value of the U parameter should be, and we propose that, if one intends to study catalysis, U should be chosen to fit the reaction energy for the oxidation of Ti2O3 to TiO2. We show that the value of U derived in this manner provides additional improvements in the description of the electronic structure.